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MG TD TF 1500 - Starter Troubles

Good day all:

Please bear with me as I try to compose this in a manner that even I can understand !

Prior to putting TD3191 on the road in 1974, I received a wiring harness that I later discovered was for the later TD with the separate fuse box, diagram W. 20451. Being a little more of a "green fish" than at present, all I had was the wiring diagram W. 77341.

When I later located a proper diagram for the control box in question, W. 20451, I wired it up using the later loom following the terminal points A1,A etc.c filing in the correct coloured wires. All seemed to be spot on, and I ran the car that way until 1993 when I mothballed it to work on a TC.

After rewiring the car, a short time ago, using the same loom (I had stripped and repainted the car in its original colour scheme), I found a # 33 Brown wire at the control box end of the loom, and I know I had secured it in the past, as the end showed signs of being flattened by a grub screw. However; I cannot recall, for the life of me, at what control box terminal, if any, I had attached it ? But, I am sure I had attached it somewhere and to make matters worse, I don't see this wire shewn being at any terminal on either style control box. Yes, I am now totally confused !

Someone suggested that I tape it off to avoid troubles and forget it, so I did.

Today, I went to fire up the TD, using jumper cables (heavy duty made from welding line). I attached the negative battery cable to the the starter switch and one end of the jumper cable to the negative battery cable. The other end of the negative jumper cable I clamped to the negative post of a 12V battery.

The positive jumper, was grounded to the block and when I touched the cathode of the battery, the engine turned over ! But, I had forgotten to turn on the ignition key so that should not be--correct ?

Further more I had no headlamps, tail lamps, side lamps etc., when I did activate, well turned the ignition key to the on position, or turned on the lamp swotche. Again though, the engine kept turning over all the time !

I crawled under the dash, which at 72 I found a little more difficult than back in 1993, armed with the diagram. I know you look through the diagram, I hold it to a light source, to get the proper way the instruments sit on the cluster plate and the wiring will be per the scematic and all looked in order.

OK; if you are still with me, here it comes. I know I am as thick as two short planks in the electrical field but something is definitely by-passing the starter/ignition system. Could it be the switch itself ?

Lads, I am at a loss and I throw myself upon the wisdom of those well versed in automotive electrics: HELP ! Please !

Respectfully submitted:
Jack Emdall, New Westminster, British Columbia, Canada
PS: The TC wiring is, I would say identical, to the early TD, I did it and it works tickety boo ! So a've I muck'd it oop again, eh !












kernow

Sounds like your thinking is in the correct direction: "Could it be the switch itself?".
I would take that one out of the circuit first and test for continuinty with no connection to power.
David Sheward

Jack, the 5 post control box has a brown wire tied to terminal A1 of the fuse block. This is connected directly to the ungrounded terminal of the battery via the starter switch terminal. Another brown wire is connected from the starter switch terminal to the ammeter, thence to the inspection socket. The 9 post control box doesn't have the brown wire going directly to the fuse terminal.

If the starter turned over when you connected the jumper cable to the battery you either have a shorted starter switch or you connected the negative power cables to the wrong side of the starter switch. There is no need for the ignition key to be in the ON position for the starter to operate. Is there any chance that you did connect the negative cables to side of the starter switch that has the cable going to the starter? Bud (77)
Bud Krueger

If I'm reading this right ...that switch has been sitting unused for 19 years?
IMHO: If it was a "repro switch" from back then very possible it went bad just sitting.
I put one of those on my car years ago and it didn't last very long. Ended up rebuilding my orginal and it has been in service for over 10 years now.
The repro was not very well built!
David Sheward

Good day again all:

Firstly; for Mr. Sheward, the switch is an original and came with the car in 1971 (Lucas part # 764401 is pressed into the body). However; as you read it has been sitting idle for about the same time period to which you referred. No doubt, I will see to changing the existing switch.

I understand that there is no # 33--Brown Wire, terminating at the RF 95/2 Control Box (as per Wiring Diagram # W.77341). Therefore the later styled harness I have, as I wrote, leaves me with this superflous # 33 wire at the Control Box terminal bank.

I see, and again it was brought to mind by Mr. Kreuger, that on the later Wiring Diagram, # W.20451, a # 33 Wire does exist and that it, indeed, affixes at the A1 point of the separate fuse box.

Again, as in my first enquiry, I mentioned the fact that I had affixed the wire in question, at some point and evident by the squashed feature of its wire strands, somewhere, but where ! Time, on memory plays nasty tricks.

When I compare the two Wiring Diagrams, I see no wire routing that tends to bind the five terminal box to the separate fuse block.

As the # 33 Wire is terminated at the A1 terminal of this block, would I be at liberty to fix my vagrant # 33 to the A1 point of the nine terminal box instead ?

I rather think that is where I did have it set before and I know that combining two wires, of different colour codes, also reads as being disaterous (ie: # 36 Brown and Blue and #33 Brown both at A1).

Whilst trying to isolate my current problem, though, I have touched this wire, to the A1 terminal, without any display of anger occurring within the system.

I reckon I could isolate it to ensure it not fouling something, but again, I thought it would look just a wee bit more tidily if it was secured.

I shall also recheck the pathways, from the switch to battery to ammeter, but I feel that is not where my problem lies.

Thanks again chaps; respectfully:
Jack Emdall, TD3191, New Westminster, British Columbia, Canada.



kernow

Bud is spot on. You connected your battery cable to the side of the starter switch that goes to the starter. You need to attach it to the side that goes to the wiring harness. When you attached the cable to the wrong side, there is no power as well to the wiring harness, so there is no lights, etc.

On a nine post regulator you don't want your 33 wire on terminal A1. Your ammeter won't read among other things.
Dave Braun

Sounds to me like Bud has you sorted out?

Not too sure what is being supplied for "switch" these days.
I do know that about 10+ years ago a batch of them were on the market that were ...to put it nicely...junk!
Many of them found their way to ebay auctions at a discount price. (where I got one)

You may be better off with your old one, or re-building it as I did.

Cheers,
David
David Sheward

This thread was discussed between 19/04/2012 and 21/04/2012

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