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MG TD TF 1500 - ignition warning light on-help!

Hi all. I know this must be in archives but...

Just cranked the TD up first time in a week. Started right up as usual. Igntion warning light dim at first, then goes out when I give gas, as usual.

I get ready to drive away, give it gas, and WHOA! Ignition warning light now gets BRIGHTER the more gas I give it!! I shut down. All wires look tight, nothing out of place. Brand new wiring harness. No mouse damage visible. I try again. Now ok! I drive a block and the light comes back on FULL BRIGHT! I head home quick!

Battery checks ok at 12.6v accross the terminals. I discover if I wiggle the light a bit the light goes out. This is a brand new light from LBCO installed this winter by me. Has worked great till now. Both wires on the light are intact. No unintended grounding I can see. Generator belt new and turning just fine. Please don't tell me my generator is kaput?

Sure would like to take a drive. Any suggestions are welcome!


efh Haskell

What is your amp meter reading when this happens?
Also ...this is a long shot:
If you have a battery cut-off switch make sure it is fully "engaged".
Mine blinked a couple weeks ago ...then the car went full dead. Coasted home to find I had driven home with my cut-off switch not fully engaged.
David Sheward

The ammeter shows a good charge when I rev it up. No changes there. I do have a cuttoff switch and all seems intact there.
efh Haskell

Remove bulb...problem solved.

I'd say you have a problem with the voltage control box. You need to test it. This

should explain how to do it.

A R Jones

>Battery checks ok at 12.6v accross the terminals. I discover if I wiggle the light a bit the light goes out.

1) Measuring the battery voltage without the motor running just tells you the battery is connected.
With the motor the voltage at the battery should be 13 to 14.5 V.

2) If wiggling corrects the issue the light ground may need to be cleaned up.

Jim B.
JA Benjamin

1) good idea, I will check.

2) this light does not get grounded. it lights up because it's ground is at control box until engine fires up. Are you saying it is getting grounded elsewhere where it should not be? if so, I can't find that place.

I fiddled with the light some more and the problem went away "for the moment". This is very intermittent.
efh Haskell

DC has to have a posative and a ground or it won't work. Try a little emery cloth and some diletric at your connections.
(I like LaVern's fix on those pesky "check engine" lights on new cars also.)
David Sheward

Sorry David S., but DC just has to have a different potential at each side. In this case it's the battery on one side and the generator output on the other. The side that goes to the generator output is a brown/white wire that is tied to the 'A' terminal of the regulator. This wire making occasional contact with ground would cause these symptoms. Bud
Bud Krueger

Soo this new light was replaced during restoration?? And you can't tell if the old light worked and gave the same symptoms???


I vote with AJ. Run the voltage regulator diagnostic.
And check the generator.

Dave Braun

I said ground, I should have said "return lead"

Jim B.
JA Benjamin

clue #1
"The ammeter shows a good charge when I rev it up."
clue #2
"Battery checks ok at 12.6v across the terminals."
clue #3
"I discover if I wiggle the light a bit the light goes out. "
clue #4
"This is a brand new light from LBCO installed this winter by me."

The fact that the ammeter still shows charge, even with charge light lit, would indicate voltage regulator and cut-off switch are still doing their jobs. A healthy battery would lean towards good regulator, too.

confirm with voltmeter, as Jim Benjamin outlines...
"Measuring the battery voltage without the motor running just tells you the battery is connected.
With the motor the voltage at the battery should be 13 to 14.5 V." Just remember to rev it up over 1000rpm.

Bud's right on this one, that bulb is not grounded, as designed. If it grounds anywhere, it can glow bright... and if a solid short, OH NO!

That area on the instrument cluster is quite congested, and I'm not a fan of the pointy screws like the one that attaches one ignition warning wire into the ignition switch. The other wire runs directly to D on the regulator. There are no bullet connectors, originally anyway.

I'd look for a stray strand at any of those connections, or worn insulation rubbing elbows with metallic parts.

A word to the wise, don't substitute an LED for an incandescent bulb. The LED will be annoyingly bright at idle, where a filament bulb is unnoticeable. I made one work, but it took a while.

Jim Northrup

Jim has a good point. Check for a short to ground.

Mike TD/TA

Okay guys, thanks for the input. To clarify, prior to resto this car didn't have an ig. warning light. It was toast. Pix below is how it is now. I'm off to the garage to do these tests.

However for me to understand what is going on here I think I need a 100% understanding of the ig. warning light's circuit. I think I have a 50% understanding at this point. So here goes, please bear with me:

1. With ig. key in off position, no juice (electricity) gets past "A" terminal on ig. switch, so light is off. Cool.

2. I turn key on (motor still not running). Juice now goes from "A" to "IG" terminal down wire #9 (white) to warning light, through resistance coils, through light bulb filiment, then down through #25 to "D" terminal on control box, thence to regulator frame to "E" terminal (earth/ground). Circuit complete, bulb glows dimly (because of resistance coils). This is the 50% I understand. Right so far?

3. I then pull starter. Engine starts, dynamo turns. This is where I'm fuzzy! Obviously something happens on #25 from generator back to "D" terminal on control box which somehow makes the light go out. Can someone please tell me exactly what is SUPPOSED TO happen (and why) at this time that makes the light go out? If I know how it's supposed to work I can figure out why the light gets VERY bright when I give it more gas (sometimes) instead of going out.

Sorry this is so complicated, but, hey, this is complicated! That "ON NO!" comment of Jim's above has me shaking instead of out driving! No Lucas smoke, please!! Is this a fire danger?



efh Haskell

Having had something similar in times past I temporarily solved it by pulling some fine sand paper between the points on the voltage regulator. In the end it needed a replacement regulator.

May be worth a try.

Ian Bowers

Ed, in your #2 above you might note that the 25 wire connected to the D terminal of the regulator is also connected to the armature of the generator. If the generator isn't turning, this is a path to ground through the armature windings. That is why the ignition warning light burns brightly when the key is first turned on. When the engine starts, and the generator begins to create an output, this point is the output voltage of the generator. The ignition warning lamp is essentially configured to be connected between the battery and the generator. There's a bit more information about the warning lamps on my site at Bud
Bud Krueger

Bud, thanks for the reply. You say:
"The ignition warning lamp is essentially configured to be connected between the battery and the generator."
I guess you mean this happens once the generator is generating juice, correct? If so, I'm trying to follow that on N.22 wiring diagram and can't see it. I see where the juice would eventually get to the A3 fuse and that's it but where does the battery come into that circuit? And I still don't understand why the light would go OUT when juice is flowing from generator up #25 either. If you could explain in the simple layman's terms I think I could get it. (Fyi, I just read all 31 pages of AJ's tech course above and it just doesn't go into the warning light circuit in much detail.)
Thanks again,
efh Haskell

Hi Ed,
lesson 5 it explains everything.
download the files but dont try to print them it will wear your printer out! don't ask how I know.
Ray TF2884
Ray Lee

Bud, I just re-read your post (for the 50th time) and maybe I just got it. Is this what you are saying:

1. Ignition key on.
2. Power goes from IG terminal to light thence to D via #25, thence to armature on generator thence to generator's ground. Circuit complete, light goes on.
3. Start engine.
4. Armature turns, juice goes other direction from generator up #25 to D, thence on it's journey to usefulness, effectivly cutting off the ground that the light was using in #2 above. So the light GOES OFF!

So if my light stays on with engine running the juice is still running up #25 to the light and the light must have found ANOTHER GROUND (aka "short"). So I've gotta find this short - good luck!

How does this sound?
efh Haskell

Ray. Thanks! This is the same correspondence course AJ sent me a link to above. However your link shows me ALL the topics in this course. I found my answer in lesson #6!
When the engine starts and the gen. builds up 12 volts it "opposes and equalises the battery voltage previously applied to the lamp and no current will flow through it [the lamp]. The light goes out".
So either my generator has "ceased to charge" (unlikly since ammeter shows a charge and light brightens when I rev engine?), #25 wire is defective (unlikly since it's new), what else?
efh Haskell

You've got it, Ed. Notice the other #25 (yellow) wire that goes from the Regulator D terminal directly to the generator's D terminal (D=Dynamo, F-Field). Bud

BTW, re: your "what else?" I'd be inclined to check out that #9 (white) wire that's connecting your ignition light to the IG terminal on your ignition switch.
Bud Krueger

Just back from garage with a few test results:

1. Visually inspected points in control box with eng. not running. Look ok, function ok, but not sure how old they are.

2. Checked battery between terminals running eng. @ 3,000rpm. Got about 14V. Good.

3. Checked all pertinant wires for visible problems. None found.

4. Armature test: Disconnected both wires from generator. Checked voltage from armature @ 3,000 rpm. Got about 2.6v. Ok I guess.

5. Generator test: same as #4 but leave both wires connected to generator. {Did not do this test yet}.

6. Disconnected BOTH leads from generator thus removing any possibility of warning light ground. Turned key on and warning light GLOWS VERY DIMLY!!! How is this possible? Seems like the light must be grounding somewhere else, no???

7. Reconnect #25 to generator (#29 still off) with key still on. As expected, light gets brighter as ground completes.

8. Disconnect #25 and reconnect #29. Light still pretty bright! How possible? Is there a short between field and armature's ground inside generator?

Tired...more later. Car still not drivable imo. Comments?
efh Haskell

Sorry Ed, but you're grasping at straws and making statements that just aren't true. For instance #6, "removing any possibility of warning light ground". I just measured the resistance between terminal D of the regulator and terminal E (ground). It's about 100 ohms. That's enough to allow the warning lamp to glow. Your problem seems to be with the warning lamp circuit, rather than with the generator. I'd suggest monitoring the generator output by connecting a voltmeter to the output (regulator terminal D) and see what's going on.

Good luck. Bud
Bud Krueger

Ed, I'd like to suggest something, but it's a pain to do. First -- disconnect the battery to avoid losing smoke. Now, if you're limber enough to get at the back of the ignition warning light, disconnect the white wire from the light and tape it up for safety. Now connect a new wire to that terminal of the light and run the wire directly to the A3 terminal on the fuse box. Now reconnect the battery and try the system. If it behaves as it should the problem is with the old white wire. If not, I'd try swapping the wires from the ignition warning light and the petrol warning light (both wires, both lights). The problem could be in the light socket. Good luck. Bud
Bud Krueger

Bud (et al),
I just tested continuity between D & E on regulator box. You are indeed correct! This is exactly why I originally stated (way above!):
"...then down through #25 to "D" terminal on control box, thence to regulator frame to "E" terminal (earth/ground)."

I understand your concern about my white wire from IG to light but it's brand new, like all my wires. And even if it was "bad" how could this cause my initial problem?

So we have discovered that the warning light indeed has MULTIPLE GROUNDS! I also just disconnect #25 at the D terminal and, indeed, the "dimly glowing" light stopped glowing instantly! We've proven that. I've not seen this documented anywhere so I guess we should be "chuffed" about that, eh?

However I still have the intermittent problem of the light coming on brigtly and progressivly when I drive. Note there is another gent with a brand new post with the same problem, proving I'm not totally crazy!

I also just tried something else. I checked continuity between both terminals on back of light and my metal control panel. I was assuming these lights were totally insulated from the panel but I do have continuity there! I also tried my new (and as yet unsed) petrol warning light. Same continuity. Shouldn't these lights be totally insulated from the control panel somehow? I'm not sure how because the spring that holds them in place touches parts of one terminal and touches the control panel on it's other end. Have I installed these lights wrong? Suggestions, comments?

efh Haskell

Ed, your warning light should not be electrically connected to the panel. I just had a look at a spare warning light and found that if the light is installed correctly the spring is not even close to the terminals. Are you sure you have the horse shoe shaped clip in the groove of the body of the warning light? Your spring lightly touching the terminal is probably the reason the warning light goes on and off as you wiggle it.
Cheers, Hugh Pite
H.D. Pite

Thanks for the quick response. About 1/2 way up this thread I had posted a picture of my light from the rear. Can you take a look at it please and tell me if anything is obviously wrong? I had a bear of a time installing those clips and getting my head in there to really see it now is almost impossible, as you know I'm sure. I'm not sure what is going on, but I am sure I have continuity as I said above (I'm using a volt meter with a continuity tester by the way).
efh Haskell

Ed, I could not really see if your installation is correct. Here is a picture of an assembled warning light.
Cheers, Hugh

H.D. Pite

Ed, I think Hugh has it. There is a solder pad on the outside of the lamp socket that can make contact with the spring mounting mechanism. Let me see if I can get some images of that area. Bud
Bud Krueger

Bud, I may have to pull my dash (again!) to really see what's going on. I'll wait for your pictures first however. Not a fun job:(
efh Haskell

Ed, what about a mirror and a torch. Good luck, huib
Huib Bruijstens

Huib, "a torch". Don't tempt me! (but I guess you mean a flashlight). I tried the torch/mirror but I can't get it in focus with my old eyes in those tight quarters.
efh Haskell

I'm sure Huib meant torch in the UK sense, on this side of the pond a torch is an oxy-acetelyn device that melts metal. On the UK side a torch is a device that lights up whatever you want to see.

As Winston Churchill said "we are two nations separated by a common language".

Bob Jeffers

My dash is apart just now, I rebuilt the lights last winter. Here are some pictures if they help

Jim B.

JA Benjamin

And another view

2 of 4
Jim B

JA Benjamin

a different view

3 of 4

Jim B.

JA Benjamin

Laast one, looking down

4 0f 4

If you need some other view just ask.

I have pictures of the lamps apart during rebuild.

Jim B.

JA Benjamin

Sorry, Ed. Nothing that really shows it. On Ttalk, at I show the lamp mounting. Under the red cloth tape is the resistor wire that creates the 70'ish ohms. The wire is very thin with a very very thin coating of insulation. One end of the wire is soldered to a connector that's attached to the center post of the socket. The other end goes to a solder pad that is connected to the bulb mount inside of the socket. See for a look at how the wire is wrapped around the socket. If the wrapping has come loose it's quite possible for the wire to be in contact with the horseshoe clip, thence to ground at the instrument panel. Ed, is this a new socket? Could have been made wrong. Unfortunately, the socket has to be removed through the front of the panel, so it's a pain to take out. You might try swapping wires with the petrol lamp and see if that takes away the symptoms. Bud
Bud Krueger

Tipping the dash forward is about a 10 minute job.

Remove steering wheel with the splined shaft attached.

Remove the eight securring screws with the decorative washers.

Place a pair of long clamps on the lower dash and put padding on them.

Tip the dash forward and work in comfort.

Hope this helps,
Dave Braun

Ed, here's an image from Patrick Earles that shows wiring issues around an ignition lamp socket. Bud

Bud Krueger

Here is the lamp holder apart.

My resistance wire had broken and I made crimps to rejoin the wires.

Jim B.

JA Benjamin

Thanks guys. I bit the bullet and pulled my dash (30 min, not 10 Dave!) 3 pictures tell the story. Would appreciate your thoughts:

Pix below shows several things. First of all, my "new" lamps (LBCarCo a few months ago) do NOT have the nice red protective tape everyone else seems to have over the resistance coils. One of them has a pathetic strip of something about 1/8" wide, but the other has nothing! As you can see the 1st loop of the coil has slipped down and touches the U-clip which touches the ring which touches the spring which touces the metal control panel! Secondly notice the end of the tiny yellow wire also touches the rings on both warning lights. The U-clip, I can assure you, is in it's recessed slot. This would indeed cause a short, no?

efh Haskell

Next picture shows me doing continuity test on ig. lamp. Both lights (petrol not shown) have this continuity between either terminal and back of metal control panel. "Shrt". Not good!

efh Haskell

You'll notice that I elected to put the U-clip INSIDE the ring rather than over it like most pictures show. That way there is no way it can pop off over time. This should have no effect on anything I can see? Am I missing anything?
efh Haskell

I too have suffered this problem.

When the dynamo is spun up the voltage increases at Terminal F BALANCING the current flowing through the bulb from the battery at Terminal A or is it A1. This balancing act makes the light go out.

I traced my problem down to incorrectly set and corroded points in the control box. I would put a bet on your control box being the cause of this problem. Before you take the dash off take the control box out and go through Section N12 of the WSM. It's not too difficult.

A R Jones

AJ, see my last 3 posts above yours (must have crossed in the mail)...what do you think?
efh Haskell

I have a TF and the bulb arrangement is different from yours. From my experience this is not a grounding problem. The system works by balancing the current from the battery with the output of the dynamo. When the dynamo generates enough current the light goes out.

I now that the control box looks like a magic box but if you follow the instructions in the WSM regarding the cleaning and setting of the points its very easy to recondition the thing. I would spend some time doing that to eliminate the control box. I suspect it isn't regulating the current properly. It fixed my problem. The other thing you might try before you do that now you have the dash out is to take the bulb holder out of the dash and let it hang in mid air. There's no chance of it grounding then.

A R Jones

That explains it, Ed. Next question is what to do about it. I thought that Jeff (LBCarCo) sells Moss stuff. Are those what Moss is selling now for warning lights? Bud
Bud Krueger

I have been reading the post with interest as I am one of the many that think electrical is basically magic! I pose the question.... If the generator has not been polarized when the system was reconnected, would it cause the same sort of symptoms? I know it says that his system is charging, but could it charge without being polarized?
C.R. Tyrell

Retry your test on the lamp-to instrument cluster, but disconnect the wires to the D terminal on the regulator.

It is absolutely critical your socket doesn't conduct to the instrument panel, but...

your previous test should indicate some continuity to ground, because you still have the armature circuit connected to ground. Your "Shrt" will probably turn into a "1" or infinite resistance, (hopefully).

Jim Northrup


SVC has some nice looking warning lights:

Maybe I missed something, but have you checked the resistance coils?

J Barry

That "nice red" material on my lamps is red Duct Tape. The original was cloth and in bad shape. There was no way I could reuse it.

The red duct tape did the job nicely.

Jim B.
JA Benjamin

"Retry your test on the lamp-to instrument cluster, but disconnect the wires to the D terminal on the regulator."
Are you referring to the fact that the light glows very dimly even with the 2 wires pulled at the generator? If so, yes, I did try removing the wires at "D" also and the glowing did indeed stop! I mentioned this way above in a response to Bud. If that's not what you mean, I'm not understanding you.

AJ, yes, I will pull the regulator and do the tests but don't you agree that I have an obvious, visible short to the control panel from these lights (see my recent pictures above)?
efh Haskell

Jim N.
I may have just figured out what you mean. Please confirm with me after reading on.
With the dash now out I just removed the yellow wire at rear of ig. warn light and my continuity test now shows no continuity (no "Shrt") with control panel at all! I must be getting tired. All I was doing was sending MM's current through the control panel's ground and it was coming back thru the yellow wire (because it is grounded at the armature as you said) and giving me "Shrt". That said, I guess my lights are NOT shorting out to control panel after all! (Bud?) I guess I better try AJ's advice and test the regulator next.
When will this thread ever end? I realize it's now too long to be followed by anyone, including me. I'll start a new one when I resolve this.
Thanks for hanging in there all!
efh Haskell

"I'll start a new one when I resolve this"
IMHO: Don't do that will make it easier for the next guy searching the archives to have the solution in the same palce!
Over the years I hit a few of those "unresolved" threads....frustrating.
David Sheward

You said-
"Next picture shows me doing continuity test on ig. lamp. Both lights (petrol not shown) have this continuity between either terminal and back of metal control panel. "Shrt". Not good!"

When you did this test, obviously, the ignition switch was off, BUT, if the wire was still attached to the regulator, your resistance test would ground out through the regulator... that's probably why you got your "Shrt."

Even if you pulled the generator wires off, the ignition lamp will still ground through the regulator.

If you disconect the wire to D, you then may hunt down your intermittent grounding.

I don't want to confuse your issue, but is your gas tank really low or topped up. If your level is low, your petrol light SHOULD be grounding. If it is full, does that light stay on all the time?

Confused yet?
Wait till you read my next post!

Jim Northrup

While not great on electrics, I just went through this thread. Ed, it is obvious from your picture that 1) the clip/cupped washer are assembled wrong (see the picture of the light near the top of the thread for correct order of parts), which puts the edge of the cupped washer much further out toward the end of the lamps and 2) the clip/washer is shorting to the resistance wire. That appears to be the problem. That would also explain why wiggling the lamp would make it go out. Fix the short from the resistance coil to the washer/clip and assemble correctly. If your ammeter was still showing charge, your regulator, generator, etc. are all fine. Totally zero chance the generator would have to do with the light being on if the ammeter was charging normally. Or take the bulb out as LaVerne said about 50 posts ago. End of problem . George
George Butz

How's your ignition switch been behaving lately? I could ask how old it is, but I have a feeling it is about the same age we are. Maybe it has arthritis?

Try turning your key on and off a couple dozen times to clean the contacts.

If you have a poor connection between the switch contacts, from A to IG, it is possible the battery voltage is dropping out and your ignition lamp is responding properly as the generator voltage is higher than the battery side.

Also, doublecheck that both wires screwed into the IG side of the switch are firmly tighten in. If they are twisted together but sloppy in the terminal, you can lose the battery voltage this way also.

By the way, the ladies are bigger offenders than the men, but 5 lbs of keys dangling in the ignition switch doesn't help.

Jim Northrup

I think George has it. After looking at your images, the cupped washer IS UPSIDEDOWN. That washer should be cupping the spring and not the clip. Sure looks like resistance wire contacting that washer.

Have fun with it!
Jim Northrup

Cupped washer: I mentioned above I think the U-clip should go INSIDE the cup of this washer! This will prevent the clip from popping out I figured. Look at J. Barry's link from above:
Looks like SVC agrees with me, no? I'll try your way and see it's effect however.

I did just notice that my U-clip was "riding high" in my photo however. I pushed it back down and that helped I think. I also added a little tape to keep that hanging coil up where it s/b.

Jim, I think we're saying the same thing about the cont. test. Removing yellow wire from D solved that. I understand now.

Ig. switch is pretty old but seems to work fine. I understand what you mean about gen. overpowering battery but this happened very suddenly. I'll clean the switch while I have access however.

Will advise...out for now
efh Haskell

My cupped washers are 'upside down' and I did so to retain the clips. My lights function fine.

Dave Braun

Hi Dave, Upon further review, flipping the washer would have the same issue: misplaced and non-insulated windings shorting against the washer and the clip. I still bet that it the problem- move the windings for clearance and tape/insulate them as was done originally. George
George Butz

Just catching up. A couple of points.

I mentioned above that if you think the bulb holder is shorting to the dash perhaps you should remove it from the dash and hang it on the wires in mid air where there'e no chance of it Earthing, start the car to see if it fixes the problem.

Another point. The ignition switch is connected to the light switch terminal A. Have you checked to see if terminal A is Earthed?

I'm not sure I understand Jim's point about poor connections between A and IG. The system is designed to charge the battery so the dynamo voltage will be higher than the battery voltage. The control box is there to regulate it to make sure it doesn't riase above 16 volts'ish.

Re-reading the above, I'm confused as to whether you checked the open circuit Regulator setting as described on page 22 of the Lucas manual, the one where you disconnect the wires A and A1 and twist them together. This is the test that determines whether the dynamo and control box generate enough voltage to balance the battery voltage.


A R Jones

Dave, thanks for the info. I went ahead and removed both my lights and wrapped the coils with elec. tape the way they should have been in the first place (thanks Moss!). I then managed to replace one light using the spring/clips the "old" way. I then managed to completely destroy the other light trying to get it back in-broke the edge of bakeolight where clip goes right off. I submit the springs/clips were one of the reasons MG did not survive, along with the pedal box, et al. But I got the light back in!!! Anybody want to guess how? I'll tell you how. Tossed the spring in the garbage where it belongs, cleaned everything up and broke out the SUPER GLUE!!!! So far it seems pretty tight. It weighs nothing so I'll wire it up and hope for the best.

Never did really find out reason for original problem (see 1st post above). I'm just gonna assume a short and it's fixed with tape. Time will tell. I'll post when it's all running again.

Thanks to one and all for their advice once again!
efh Haskell

Ed, It is sure not exactly a brilliant mounting arrangment! What were they thinking? Hope it is fixed. Maybe if you need it, you can find a good used one on ebay. I bid a few bucks on a real NOS one a couple weeks ago- it ended up going for over $100 I think. George
George Butz

it ended up going for over $100 I think.

I am glad I repaired mine.

Jim B.
JA Benjamin

Dear Ed

I have been in and out of this discussion over the days, but not had enough time to say 'whoa', and why I am sure the problem lies with your voltage regulator. Your analysis makes no mention of the function of regulator switching in your curcuitry, but it is there and has a role.

It is now 3:00am, and we are off to Spain in the morning, so I have been lying awake thinking that it is now or never!

Point 1: electricity is not only about volts but also amps. Light bulbs are measured in watts, the multiple of V*A, and the brighter the light bulb the higher the watts. Your light bulb keeps getting brighter; clue?

Point 2: Generators create near constant volts (yours is marked 12V somewhere on it). It is the amps which rise as the engine speed rises. If the regulator did not kick in the bulb would burn ever brighter as the engine speed rises, and the battery would overheat.

So, the bulb does not go out because of rising volts pushing back, as you suggest, it goes out because the voltage regulator receives enough amps to trigger the VR switch (coils receiving enough amps to throw the magnetic trigger) and stop the excess current into the battery. There are two coils, so it is a bit more complicated than that, but the problem is too many amps, not volts leaking. If it was a short anywhere Lucas smoke would pop out.

For some reason your VR has decided to play up. Beg, borrow, steal or even buy a known working VR and see if that solves the problem. It is only a 60min job to swap VR's over, but does involve unpicking some of the tool box felt.

Well, that is how it seems to me.

And as an aside, I lie awake worrying even more about the Euro, we are damned if we do nothing about it and pay Greece, Spain and Italy's bills to go on living beyond their means, and damned if we do even let Greeece default on its debts. Hopefully there will still be some paper Euro's circulating in Spain for the next two weeks, not all hoarded under their beds.

Now back to bed, and hopefully to sleep!

Ian Bowers

Ian, I thought I was the only one who dreams about this stuff instead of sleeping! Rest assured I am going to do a set of control box and generator tests before I drive it again. Of course to do that I have to start the engine. To do that I have to install the dash & oil/water lines to the gauge again. I'll post those results here for any future reader.

Go back to sleep now and think about those tapas bars in Spain instead of amps! And post some pix of that newest toy sometime too.
efh Haskell

Still sounds like a slipping fan belt to me.
M Blencowe

Hey Ed.. How does this story end? Cheers
Peter TD 5801
P Hehir

This thread was discussed between 14/05/2012 and 30/12/2014

MG TD TF 1500 index

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