burnt wiring to square relay, WHY??

mr bump

mr bump

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The car, 72 cs coupe 3.0 has been laid up in the garage for 5 weeks while i fit a new diff, connected the battery, turned the car over and smoke started to come up from the square relay near the bettery, as you can see from the pic, somthing has caused the wiring to burn. Whats caused this to happen??:(:(
 

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That is your regulator, not the relays. Very common for the insulation on these three wires to crack and crumble causing a short. There is a three prong plug at each end, remove and find the fault. You can replace single wires or buy a new harness.
 
HB Chris said:
That is your regulator, not the relays. Very common for the insulation on these three wires to crack and crumble causing a short. There is a three prong plug at each end, remove and find the fault. You can replace single wires or buy a new harness.
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You are a star chris, been worried like mad for the last hour, its my youngest daughters prom next week and ive promised to drop her off in my coupe....think you just might have saved it, il let you know how i go on.

Thank you chris.
 
Just stripped the wiring out, and the black seems ok, the blue seems ok, but the brown is well burnt!...is the voltage regulator at fault? or just old wiring? Its been fine up until now, can wiring strike when you least expecting it?
 
Nice greeting when I took the glove box out!! This red/chard wire goes through into the engine bay, anyone know what this wire is??
 

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mr bump said:
Just stripped the wiring out, and the black seems ok, the blue seems ok, but the brown is well burnt!...is the voltage regulator at fault? or just old wiring?
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Hard to tell whether the fault is with the wiring or regulator. As Chris wrote "Very common for the insulation on these three wires to crack and crumble causing a short". So, if TWO adjacent wires lose their insulation, they can short to each-other. Or if your brown wire lost its insulation, it might have shorted against some grounded sheet metal. From your photo, it's imposible to tell if either of these scenarios took place - can you do some detective work, and see what might have caused a short?

If nothing looks wrong in terms of the brown wire shorting, then the regulator or alternator probably are at fault. I suppose the simplest way to debug it would be to replace the burned wire with an inline fuse (say 5a), start and rev the engine, and see what happens. If it's the regulator or alternator, the fuse will blow.

According to my wiring diagram the brown wire is D- between the alternator and regulator. Dunno how that helps you, but I can confirm that it is not the wire going to the warning light on the dash (that's the blue one).
 
Bummer...

Make sure to check your battery. I have seen this many times when the battery has "bridged" Mayhem...especially to the ground side of things. Much smoke and misery.
 
pamp said:
I have seen this many times when the battery has "bridged" .
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What does "bridged" mean in this context? I did an Internet search on the term "bridged battery" and came up with the definition: "A battery intended to provide power to system memory while the main battery is replaced" which doesn't sound like what you are referring to.
 
Pamp, Jmackro, thank you for the posts aswell as Chris, aswell as the regulator wires burning through it's also the two red wires from the fuse box area leading through to the battery terminal, they are burnt quiet bad aswell. I've looked on the net and read what is available regarding this type of thing and I think I've got the answer...........Bad earth or not enough earth.

When I did the gearbox conversion, I forgot to reattach the earth strap to the bell housing, so it's just been doing nothing basically, and the one and only earth strap, the plated metal type, is not the best looking thing and wasn't doing its job too well.

So, here's what I'm going to do. New main red cables through to the battery with a 10 amp inline fuse in both, new battery to body earth strap, lets say a 10mm cable, and I'm going to put another 3 new earths in aswell. One from the bulkhead to the gearbox, gearbox to engine mount, them engine mount to the negative battery. That should earth it ok.

If the car had of started and I'd have gone into the house for my usual coffee and cigarette, I would have been dealing 999 emergency services than posting in here. So the cs coupe gods were certainly shining on me yesterday.

Again, thank you to all who took the time to help out
Joe, still got his 72 cs.:wink:
 

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jmackro said:
What does "bridged" mean in this context? I did an Internet search on the term "bridged battery" and came up with the definition: "A battery intended to provide power to system memory while the main battery is replaced" which doesn't sound like what you are referring to.
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Bridged in auto speak is when the positive and negative joined together via a piece if bodywork, or when the two terminals have come into contact with each other and BANG!!! I'm sure that's what was meant, because when that happens it sure ain't harmony I can tell you!!:-o
 
mr bump said:
When I did the gearbox conversion, I forgot to reattach the earth strap to the bell housing, so it's just been doing nothing basically, and the one and only earth strap, the plated metal type, is not the best looking thing and wasn't doing its job too well.
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Yes, that would explain various burned wires - when you ran the starter, the circuit needed to "find" ground connections wherever it could. I guess those alternator-regulator wires were part of the path.

The question is whether damage was done to the alternator or regulator by the excessive current. It might be a good idea to:
1) check that the alternator warning light goes out once the engine is started, and if that checks OK then:
2) put a voltage meter across the battery terminals while it is charging, and make sure the voltage isn't excessive.
 
Batterys

What I mean is that the battery bridges internally....positive to the negative plates. This happened to me on a MB a couple of years ago....it fried the security system and I had smoke pouring out the dash, dead on the side of the road with the alarm sounding. Had to move fast to disconnect the battery.
I can definately see that if the engine to body ground strap was left off this would not be good...
 
I know, a stupid mistake that ive never done before and cannot think why i failed to do it this time, especially on a car of this age. but testiment to bmw, the wiring, considering its age, has done quiet well not burnt the lot out.:sad: But hayho, im lucky i wasent driving and got stranderd at the side of the road.

But when i was looking at the wiring behind the glovebox, 2 thoughts went through my mind......1, i either need a advanced electrican, or 2, a realy good pasta chef, it looked like spaggetti!!:-o:-o:-o

but the wiring is orderd and should be done by next weekend.

My lesson out of this, Always check the earth straps and make sure they are doing what they should be doing.:-?
 
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