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MG MGB Technical - Installing/Wiring of Lucas Fog Lamps

I just got a beautiful pair of Lucas fog lamps (FT11's) and I want to stall them on my 71B. They have bullet-style connectors on the lights.

I would like to wire them up with a simple toggle switch under the dash. I suspect I should probably use a relay of some sort. Anyway, what type of relay should I use, where would I mount it, and what can I do to make this look as nice as possible?

Robert
Robert Rushing

Robert, You can find relay information at:
http://www.mgcars.org.uk/MG_Elec-Tech/relays.html
I added have relays in my headlight circuits. I mounted the relays on the right fenderwell near the the grill under the horns. They are out of the way and look neat there . Bosch is one of the better relays to use but I don't know of a local source for them. You will need a relay with four terminals the has normally open cantacts. I have been using relays from NAPA and Advance Auto, they can be found in the lighting aisle of stores like Pep Boys, Advance and Autozone.

Your console should have a blank for adding a foglamp switch. Moss switch fog/spotlight 162-170 will fit the blanks but you will also need a bezel. I drilled a hole in a console blanking plate for a toggle switch to control my cooling fan

If you need wiring instructions let us know. The switch packaging usually has wiring instructions.

Regards, Clifton
Clifton Gordon

Re: Clifton's preference for Bosch relays ~
you should be able to pick these up from a VW/Audi, BMW, or M-B dealer or Eurocar specialist parts house. Just tell them you want a single pole unit for aux. lights and they should know just what to give you. Potter-Brumfield also makes reliable auto relays as well.
Bob Muenchausen

Do relays need to be protected from weather?

What are your suggestions for grounding? Ground to the body or use the headlight grounds?

I assume I'll run the wiring from the lamps to the relay, the relay to the fuse block, then from the fuse block to the switch.

What gauge of wire should I use?

Robert
Robert Rushing

Bobert, Relays need some protection. They should be mounted with the terminals pointed down to prevent water from entering around the relay body and the plastic housing. Run a fused 10 or 12 guage wire from the starter solenoid battery terminal to relay terminal 30. Connect the lights to relay terminal 87. I would use a 10 or 12 gauge wire to a four way bullit connector and use 14 or 12 gauge from the bullet connector to each light. I would run ground to one side of the switch, any good body ground will work or you may have an unused hole in a ground bullit connector behind the console. You can use small wire, 18 gauge, as the relay coil uses very little current. Connect the other side of the switch, 18 gauge, to terminal 85 of the relay. You will need a 12 volt source for the relay coil, I would use a source that is switched on with the ignition switch. There may be a spare lug on the fuse box on the side where the white wires are connected. If none there, you can look for a bullit connector with white wires in the bundle of connectors near the right fender and bulkhead and run a small wire from the connector to relay terminal 86. Good luck, Clifton
Clifton Gordon

Sorry, I meant Robert, sometimes it seems my brain and one or two typing fingers get disconnected. Regards, Clifton
Clifton Gordon

No problem Clifton.

Let's see if I get this: I guess then I should connect the grounds for the fog lamps to the grounds of the headlights (using 4 way connectors). Run the lamps' positive wires to a 4 way connector then a wire from it to the relay. The relay has four wires going from it: the one to the lights, the one to the switch, the one to starter for 12v service to the lights, and one to a white ignition switched wire for the low current for the relay. Does the relay need a ground itself or is that provided by the ground at the switch?

Anything else I'm missing?

Robert
Robert Rushing

Robert, No ground is needed for the relay, your lights should get a ground through the mounting bolts, if they do not, a ground from the lights to any convenient point on the body will do. Regards, Clifton
Clifton Gordon

May I make a few suggestions?

1. Rather than running a wire to pin 86 from the white wire at the fuse box, connect pin 86 to a red wire (any convenient red wire will do). This way, the fod lights will only come on when the parking or marker lghts are on, and you only have to turn off one switch - the main headlight switch - when you stop and get out of the car. It's easy, at least for old timers like myself, to forget and leave them on. If you'd like a better "headlights on" reminder than most which are available, let me know and I'll post the instructions for it. You should never be using the fog lights without the parking/marker lights anyway, as you need to be visible to other drivers from the side and the rear.

2. Buy relay sockets for your relays. Makes it easier to wire, and much easier to replace the relays. You only have to remember what wire goes where once, when you install them. To replace, just pull them out and stick in the new ones - no wiring involved. Sockets may be purchased from British Wiring, http://www.britishwiring.com or from Waytek, Inc, http://waytekwire.com

3. Instead of buying the relays at an auto parts store, buy them from Waytek, part number 75102, and get the five pin type, with a second 87 terminal. These are Bosch relays, rated at 30 amp. Do NOT buy five pin relays with an 87a pin, as the 87a pin is closed when the relay is OFF. Most five pin relays have an 87 and an 87a pin. Buy spares, as they are hard to find locally. Wire one side to the first 87 pin, and the other side to the second 87 pin. This eliminates using a double bullet connector, and one source of trouble later.

4. 14 gauge wire is rated for 15 amps, and should be adequate for any fog lights you may want, especially if you use the five pin relays mentioned above. 12 gauge will be more than adequate, and 10 gauge is overkill. Nothing wrong with using 10 gauge if you wish, but the larger the gauge, the harder it is to wire. 15 amps is good for 180 watts. 12 gauge wire is rated for 20 amps, good for 240 watts, and 10 gauge is rated for 30 amps, good for 360 watts. For a safety margin, you should reduce the maximum wattage by about 20 - 30%

Hope this helps.
Dan Masters

Whoops! That should be http://www.waytekwire.com

Sorry 'bout that.
Dan Masters

I wouldn't mount the relays in front of the radiator as they catch too much weather there and have a relatively long run of unfused brown. You could have an in-line near the fusebox, but better to fit a fused relay near there instead. Neither would I rely on a body ground for a relatively large current, nor the existing headlight ground as that is already taking more than enough load on what are only thin wires. If the fog-lights are wired to only be available when the side-lights are on (highly recommended) then the relay *will* need a ground.
Paul Hunt

Paul,

If wired as described by Clifton, and as modified by me to be on only with the side lights, no additional ground is needed. Power to the relay coil comes from the side light wiring, and the ground for the coil comes through the on-off switch - one side of which is grounded.

Or did I misunderstand your comment on needing a ground?
Dan Masters

Now I'm confused. This is not unusual because I completely suck as electrical issues.

My fog lamps have two wires coming out of them - a positive and a ground. I assumed that the positive would go to the relay and the ground would just be grounded to whatever is handy such as the headlamps. However, would it be better to just ground them to the body instead?

Next, if I use a red wire as the low power to the relay so that they will only come on if the sidelights are on, I still wire it with a separate switch so that they are not on all the time, correct? I don't want them to come on everytime I turn on the side lights or headlights. So I assume that by using a red wire, that the relay will only get power when the sidelights are turned on, thus I can turn on the switch to have them come on or can leave the switch on so that when I turn on the side marker lights or headlights that the fog lights will come on everytime too if I want. Is this correct? Plus if I use the red wire, I will need to ground the relay, right?

When I run the power from the starter to the relay using a fused wire, I just buy an in-line fuse to put on the wire running from the starter to the relay. Is this correct?

I should also mount the relay in the engine bay somewhere near the fuse block, yes?

Thanks for all the help you guys are giving me. Sorry for being so thick headed.

Robert

Robert Rushing

I also do not understand the need for a relay ground other than the one through the switch used for turning the fog lights on and off. If an extra ground is needed how would a plastic bodied relay be grounded? Paul also said its best to not rely on a body ground. The battery is grounded to the body. Is this a defination problem like body/frame/unibody? Thanks, Clifton
Clifton Gordon

Robert,

You're getting close. Wired the way I suggested, the lights wil come on if and only if you have the parking lights on AND the relay switch on. The fog lights will NOT come on if the parking lights are not on, even if the switch is on. You will never need the fog lights unless you also need the parking lights.

For simplicity:

Pin 30: To the battery terminal of the starter solenoid.

Pin 87: To the fog lights. One to each fog lamp if you have two 87 pins.

Pin 86: to a red wire.

Pin 85: To one terminal of the on-off switch. The other terminal of the on-off switch goes to ground.

No additional ground is needed for the relay, nor is there any provision for one.

If you want to use a fuse, place it inline in the wire from the solenoid to pin 30, as close to the solenoid as is practical. On later MGBs, there are several inline fuses in this general area already.

The criteria for relay placement are:

1. Protect from the elements as much as practical.

2. Place them so that the length of wire from the solenoid to pin 30 is as short as practical.

3. Without violating rule #2, place them to minimize the lenght of wire from pin(s) 87 to the lights. Rule # 2 has precedence over rule #3.

4. The length of wire from the red wire to pin 86 is unimportant, as the red wires are already fused and this wire carries very little current.

5. The length of wire to the switch, and from the switch to ground, is unimportant, because these are low current wires, and shorting them to ground has no effect because these wire are shorted to ground under normal operating conditions anyway. The worst thing that will happen is if the wire to from the relay to the switch shorts to ground. In this case, the lights will come on any time the parking lights are on. A nuisance, maybe, but no fire hazard.

FOG LIGHTS

1. Connect the positive leads to pin(s) 87 of the relay. The positive lead is the one that connects to the center pin of the bulbs.

2. Connect the negative lead to ground. A GOOD body ground will work quite well. If I remember correctly, all of your lights are now grounded to the body.

As with any wiring, protect all wiring from hazards, such as sharp edges, etc, as much as you can. Use grommets wherever the wires pass though body work, and cover the wiring with either harness tape or split loom.

I believe this covers it all.




Dan Masters

Dan that was super! Very clear!!! So clear in fact that I hate to ask this one final question: what size of fuse should I use on the in-line fuse? 30 amp?

Thanks a whole lot. I can't wait to get them hooked up now!

Robert
Robert Rushing

I have the manual switch is in the red/green wire from the main lighting switch and a local ground at the relay. But having thought about it if my wiring shorts out it cooks the loom. Whereas if the relay is close to the fusebox and picks up is 12v for the winding from a red there (or from the bullet connector by the firewall on early 2-fuse cars), and the ground for the relay comes from the manual switch on the dash, if that wire now shorts out all that happens is that the relay will be operated when you hadn't intended. When I've nothing better to do I might change it.

When I said 'body ground' I should have said 'physical mounting'. These can't be relied upon as I found out with my rear fogs, one of which packed up after several years use. If there is a ground wire coming out of the lamp I would take it to a suitable grounding point on the body shell, if there isn't a ground wire coming out of the lamp I would provide one.

Dan gives a clue as to fuse size further back.
Paul Hunt

Right you are, Paul. I just noticed that he mentioned how many amps will be created by the size of the wire. So I guess the correct answer would be that the in-line fuse I'll need is according to what size wire I use.

Great stuff!

Robert
Robert Rushing

Robert...did they come with vinyl covers?

If not, Tripple C is running a special on them.

Tony
Beelzie

Doncha mean 'Trippple' C ...
Paul Hunt

Robert,

Fuse sizing is a two step process. First, you size the wire to handle the load, and then you select the fuse to protect the wire. If your lamps draw 10 amps, you will need a wire rated to handle 10 amps, plus a little margin. This would be a 14 gauge wire, which is rated at 15 amps. The fuse size, then, would be 15 amp MAXIMUM. If you should decide to use 12 gauge wire instead, then you could use a 20 amp fuse. 10 gauge wire would allow you to use a 30 amp fuse.

However, regardless of the size wire you use, there is no need to use a fuse rated much larger than the load. Even if you were to use 4 gauge wire, rated at 100 amps, you should still use a fuse rated around 15 amps for a 10 amp load. Even though the 4 gauge wire could handle 100 amps without burning in case of a short, there is no need to let it do so. If you have a short that draws more than the lamps are supposed to draw, you have a problem and you might as well blow the fuse and clear the short.
Dan Masters

That makes a lot of sense. I'm going to have to figure out what I'll need for those lamps. I'm placing an order right now for the 5-pin relay and relay housing. Wish me luck.

Unfortunately, Tony, they didn't. I am one step ahead of you and have the Triple-C catalog out right now with the item circled for Vonda to see when she gets home tonight!

Thanks for your help everyone! Not only have you helped me out but you guys have taught me a lot (except for Tony, well, ok, he's taught me a lot too; but not about electrics!)

Robert
Robert Rushing

Just one point, guys. Fog light can be used with headlights on, but (assuming US laws are similar to the UK) there are rules governing the position that the lights must be fitted, so that they don't dazzle. Spot lights, or driving lights, can be used with main beam, to provide a much higher degree of illumination, but must switch off when main beam is switched to dip beam. Just thought I'd point this out, if only for UK drivers, but there might be a similar ruling in the US.

Mike
Michael Watkins

Michael,

The laws governing auxiliary lighting in the US vary so widely from state to state they no generalizatins can be made.

One other point to be made, though, concerning fog lamps - If you are driving in fog, you should NOT have your regular headlights on at all - high or low beam. Strangely emough, the stock wiring for fog lamps on an MGB was arranged such that you HAD to have the low beams on to have the fog lights on. Weird!

To be effective, fog lights should be mounted as low as possible on the car. Fog lights have a very sharp cutoff, limiting light output to a low level, such that the light shines UNDER the fog. Regular beams, or, for that matter, fog lights that are mounted too high, just reflect off the fog back into your eyes, causing glare that severly reduces your ability to see through the fog.

If you are driving under clear weather conditions on winding country roads, you can use the fog lights as "cornering" lights, since they also have a wide beam pattern. This is the reason I recommend wiring them to be on with the parking lights. This gives you the option of driving with the fog lights on but without the headlights in fog, but with headlights AND fog lights in clear weather. Either way, the fog lights go off when you turn off the main light switch.

As a standard practice, I always wire driving lights so that the high beams must be on to use them. That way, if you dip your lights when meeting oncoming traffic, the driving lights also go off without having to remember to operate a seperate switch.
Dan Masters

FWIW, the fog lights on my 2002 Mazda will work only with low beam lights on. Maybe there is a federal standard requiring they operate that way or it may be to satisfy some state regulations. Clifton
Clifton Gordon

Clifton,

You may be right about the laws. Laws, unfortunately, are passed by politicians, not people who really know what the laws mean. The original MGBs were wired that way too, if they came with the fog lights installed.

Next time you're out driving in a fog (the weather, not you personally - I'm always in a fog myself), check out the fog pattern. You'll find that the fog usually lays several inches above the ground, so if you can get the light under it, you'll be able to see better. Light shining into the fog just bounces back off the moisture droplets and into your eyes, severely reducing your vision depth. If you don't have fog lights, often you can improve your vision by running on just the parking lights. Being lower to the ground helps, but also the fact that they are not as bright, thus don't glare back at you, also helps. When your eyes see the glare, they adjust as if they were in daylight, but you are still trying to see things that are in the dark - doesn't work very well. It's like standing under a street light and trying to see someone hiding in the bushes. Just by shielding your eyes from the light with your hand, you can see into the bushes better.
Dan Masters

Current UK regulations are that both front and rear fogs/spots can *only* come on with the headlights. Since even dipped headlights render front fogs almost useless mine are illegal.
Paul Hunt

Dan

A great comment re driving lights being wired into high beam circuit so that they go off when you dip your beams – must remember that if I install driving lights on my MGB.


BTW – I'm amazed at the number of current model cars, eg WRX, which have these massive so called fog lamps which are brighter than their low beams and which are left on in normal city driving conditions. Somewhat unsafe to cars they are following.

Peter
Peter Vann

I got an e-mail today from British Wiring, my relay and relay housing should be in the mail to me now.

Robert
Robert Rushing

'inappropriate use' of both front and rear fog lights i.e. having them on in conditions that don't warrant it is an offence in the UK risking a UKP1000 fine. Per light. Doesn't stop w*nkers having them on in urban well-lit streets in traffic and rain, though.
Paul Hunt

I'm afraid that the comment on UK fog light restrictions is incorrect. The relevant act (blah blah blah - 1989) states only that rear fog lights may not be used in a manner that causes dazzle and only in a time of seriously reduced visibility. However, it is also stated that in reduced visibility conditions, front lights (either dip beam headlights or front fog lights) must be lit.
So, you can use your rear fogs without the headlights lit as long as you've got front fog lights and they're on.
There is no compulsion here in terms of restrictions on wiring, so rear fog lights that operate independantly of anything else are, actually, legal. The Catch-22 is that if they're on and visibility is good, you're breaking the law. If they're on and visibility is poor and you haven't got the front lit up, you're breaking the law(!)
Incidently, the wiring on my '97 Disco supports this as it allows the rear fogs on with either the headlights, or the front foglights, or both.
Tim Cuthill

Whilst i am not condoning the use of fog lights as driving lights in anything other than the crappiest conditions, a properly set up fog light, is designed as described above, to have a very sharp cut off and therefore whether used in daylight and good conditions or not should not (due t the angle there are set up at and lens type) cause anymore glare in the high than standard dipped beam.

I have myself used 'under the bumper' lights in cars i have driven as an aide to driving as they certainly fill out parts of the road the main headlamps do not. Mind you, i drive mostly country back roads, where i can see the usefulness of extra lights - not much point on a lit highway!!

However i dont believe there to be an alignment check of front fitted fog lamps to UK cars during MOT tests at present, and there almost certainly should be..! For one thing a poorly set up one is going to be practically useless and second, it will cause a glare situation. Chances are the fog lamps that cause annyoance are poorly set up...

Tim's comment is an interesting one, i wonder if anybodys argued their way out of court with that..?

~PHIL

Phil

http://www.fizzindi.demon.co.uk/fogheight.htm

To use any additional front lamps *without* dipped headlights in conditions other than poor visibility, day or night, they must be between 500mm and 1200mm of the ground and 400mm of the sides of the vehicle. A quirk of lighting law (maybe 'corrected' now) says that you can drive with dipped headlights in poor visibility, or no lights at all, but you can't drive on side or parking lights only - another common sight on motorways in the rain. At one time manufactures provided a 'dim dip' headlight if the ignition was on with just the side lights, but that may have been made illegal for newer cars.

"may not be used in a manner that causes dazzle and only in a time of seriously reduced visibility" i.e. inappropriately.
Paul Hunt

This thread was discussed between 30/10/2002 and 07/11/2002

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