Burnt out earth/brown generator

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gramal

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Hi Guys,

Tried to start up the 3.0 CSi this morning, 1st time after the winter. Noticed a burning plastic smell, quickly had a look in the engine bay and the brown wire to the alternator or rely had burnt through the plastic insulation. Any ideas?

Could it be a poor earth connection or failed Regulator. Electics not my strength.

Any pointers gratefully received

Cheers gramal
 
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If you still have a regulator with three wires running to the alternator plus the thicker red positive wire from the battery terminal, then the the three wires may have shorted out and melted together. This is very common and you can replace these wires yourself, just buy the female spade connectors with the small barb that holds them in the plastic plugs at each end. Mesa Performance sells this harness with plugs at both ends. HTH.
 
In addition to what Chris said...its better to charge the battery with a charger when its been in hibernation for a long time than allow your alternator and wires to heat up and work overtime.
abe
 
gramal said:
Hi Guys,

Tried to start up the 3.0 CSi this morning, 1st time after the winter. Noticed a burning plastic smell, quickly had a look in the engine bay and the brown wire to the alternator or rely had burnt through the plastic insulation. Any ideas?

Could it be a poor earth connection or failed Regulator. Electics not my strength.
Any pointers gratefully received

Cheers gramal
Click to expand...

Are you using a stock (original equipment) type alternator with an external voltage regulator? It sounds like you might be since you mentioned a "brown wire" and that is typically the color or a ground or earth wire. That wire may look sound, but the insulation may have been harboring some internal corrosion and causing the wire to heat up. If you are running an upgraded higher output alternator with an internal regulator, with additional accessories, then the ground wire becomes even more important as it now may be called upon to handle increased amperage.

In either case, a poor ground can make for some hot wires and certain "older" insulations have a bad habit of poorly handling repeated bouts of heat.

I have a feeling that your ground wire may be too thin to handle the amperage produced by your alternator. Usual rule of thumb is thicker gauge is better when you are dealing with increased loads. This becomes more critical if your wiring is old and less capable of handling the demands for which it was designed. Since your car had been sitting, your battery may have been weak and discharged and with other accessories on placed maximum demand on the alternator's output. There are a lot of possibilities. Below is picture of good example of ground wire for what is probably an internally regulated alternator.

alt_gnd_wire.jpg


Go back and clean your grounds. If you were in the US, I would suggest you go from using probably 8 awg or smaller to 6 gauge or even 4. (8awg is good for tops 55a, 6awg to 75a see chart below) http://en.wikipedia.org/wiki/American_wire_gauge. Since you are somewhere near the prime meridian, I'll leave you to figure out the gauge thickness terminology favoured in your neck of the woods. http://www.dave-cushman.net/elect/wiregauge.html The picture should give you a decent idea though.

hth.
 
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bengal taiga said:
If you are running an upgraded higher output alternator with an internal regulator, then the ground wire becomes even more important as it now must handle increased amperage.
Click to expand...

Well, not necessarily. Just because the alternator has the capacity to put out more amps doesn't mean that the car is going to draw more amps. If it takes 15 amps to charge the battery, the ground wire is going to handle 15 amps whether your alternator has a maximum capacity of 55, 65, or 1,005 amps. I'm not saying the ground wire isn't important, I'm not saying that a fried ground wire isn't gramal's problem - I'm just saying that until you install halogen headlights, heated seats, 1,000 watt stereo, television, etc. etc. your wiring doesn't have to handle the amps the alternator is capable of delivering.
 
jmackro said:
Well, not necessarily. Just because the alternator has the capacity to put out more amps doesn't mean that the car is going to draw more amps. If it takes 15 amps to charge the battery, the ground wire is going to handle 15 amps whether your alternator has a maximum capacity of 55, 65, or 1,005 amps. I'm not saying the ground wire isn't important, I'm not saying that a fried ground wire isn't gramal's problem - I'm just saying that until you install halogen headlights, heated seats, 1,000 watt stereo, television, etc. etc. your wiring doesn't have to handle the amps the alternator is capable of delivering.
Click to expand...

Was speaking strictly in generalities and agree with you 100%. I was presupposing that an upgraded alternator may have also included other nonspecific energy consuming upgrades. Post has been edited accordingly.

In the interest of brevity, I left out the theory that if Gramal's car had a nearly-dead battery, and draw from the fuel injection pump, ignition, heater, defroster, wipers, headlamps, mobile phone/laptop charger and whatever else he might be powering though marginal wiring - during London's recent bout of inclement weather, he could have and likely did experience a brief overload on the subject wire - whatever the alternator's capabilities. However, I was also suggesting that if the amperage capabilities are increased, common sense, dictates that wiring to and from the alternator be concomitantly improved, or at least be adequate to handle any increased capabilities. The E9's wiring was probably adequate when new. The state of most E9 original wiring (34+ years later) is uh, um, err, ah . . . probably less so. Some of the wiring I've encountered lends new meaning to the word "brittle" :wink:
 
HB Chris said:
If you still have a regulator with three wires running to the alternator plus the thicker red positive wire from the battery terminal, then the the three wires may have shorted out and melted together. This is very common and you can replace these wires yourself, just buy the female spade connectors with the small barb that holds them in the plastic plugs at each end. Mesa Performance sells this harness with plugs at both ends. HTH.
Click to expand...
Hi fellow forum members, I have a question for you @HB Chris

After two weeks with my 2800 cs 1970 stopped. The other day I tried to start it and even having the new battery recently changed it seemed that the starter motorcycle had a hard time turning, after several attempts smoke began to come out under the hood.

The ground wire connecting the alternator to the voltage regulator (the little silver BOSCH box to the right of the two round relays on the right under the hood) was completely melted.
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The car won't start and I thought the wires had come together and created a bad contact.

This morning I have dismantled all the wiring in that area and I have replaced the ground cable with a new one with a slightly larger section (it was the only one I had on hand).

After trying again to start the car (already with the cables changed) they have melted again, specifically the cable that connects the alternator with the voltage regulator.


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What do you think could be happening?
 

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I'd check the main earthing straps to the engine. Had a similar problem on mine, smoke from the alternator and regulator when trying to start it - it wouldn't - until I traced the earthing problem and fixed it. The starter needs a huge current and if the earthing is bad, the current will try to find another way to complete the circuit, alternator wiring is probably the next easiest route! On mine it was a bad connection from the earth strap to the engine block.
 
What makes me doubt is that before stopping it for two weeks the car started perfectly, and now it seems that the alternator has a hard time turning.

For a month there has been a heat wave in Spain and even though I have it in the garage the temperature can exceed 40 degrees inside.

It seems that the alternator has a hard time turning, as if the battery was worn out but it is new and is fully charged.
 
day66 said:
I'd check the main earthing straps to the engine. Had a similar problem on mine, smoke from the alternator and regulator when trying to start it - it wouldn't - until I traced the earthing problem and fixed it. The starter needs a huge current and if the earthing is bad, the current will try to find another way to complete the circuit, alternator wiring is probably the next easiest route! On mine it was a bad connection from the earth strap to the engine block.
Click to expand...
How many ground points does the engine has?

I, apart from the one for the battery and the one in the center, under the carburetors that are attached to the chassis where the water pipes for the heating, do not know of any other connection that I can verify, and these two seem to be correct.
 
The ground cable on the battery can look good and still be bad, another member here had this issue with the positive cable. Clean both ends of battery ground cable and the strap from carb to firewall. For extra ground try running a 10 or 12 gauge ground wire from valve cover to body, I had to do this even though ground wires look perfect. And as an experiment, unplug the three wires at regulator, your car can start without the alternator, see if this makes a difference.
 
Since the last time I used it, two weeks ago, the only thing that was done was to change the gearbox gaskets and seals and new clutch, and I brought it driving from the workshop without problems, it started perfectly.

Maybe the voltage regulator is wrong, I could start there, the problem is that the car doesn't start and I can't make voltage measurements with the engine running, it's as if the spark plugs don't get current, at least that's what it seems.

Everything is original, the alternator is from the year 70.

When I came back from vacation and went to start it, the starter motor sounded as if the battery was worn out (it had a hard time turning) but the battery is new, but I managed to start it but in low the engine died (it turned off), it only worked in high revs, I took a lap and thought it had to do with standing still or maybe some fuel (but the carbs are freshly made by Carburadores Conrrado, which are pretty good.) The next day (yesterday) I tried again start and it cost me god and help but in the end I managed to start it but after going around the block if you didn't speed it up it would stop, after several attempts I managed to start it but it sounded bad (as if it were on 3 cylinders) and then it definitely stopped to boot.

Trying to start it over and over again is what started to smoke from the ground wire between the alternator and the voltage control unit.

This morning I changed the burnt cable and when trying several times to pull it out the new cable melted again.

I'm pretty sunk because I don't know what could be causing this problem, I don't know if the car that doesn't start is related to the burnt cable or the burnt cable is simply from trying to start it repeatedly forcing the alternator to work a lot.

I don't know what to do.

I'll be back tomorrow to change the ground cable for a new one (the one that connects the alternator with the voltage control) and I will check the ground connections well.
 
teahead said:
Uggh....I prefer using a built-in regulator alt that came with later E12s/E24s/E28s, etc.
Click to expand...
Do you think this new version would be compatible with my 1970´2800 cs and if so, are they still available to buy new?

Regards
 
I suspect your alternator has a shorted out diode. If you disconnect the big red wire that goes to the alternator bolt (the one covered by the black rubber boot) and then take a resistance reading from that bolt on the alternator to ground with your voltmeter, it should read infinite ohms (open circuit). See what you find out.
 
Luis A. said:
I suspect your alternator has a shorted out diode. If you disconnect the big red wire that goes to the alternator bolt (the one covered by the black rubber boot) and then take a resistance reading from that bolt on the alternator to ground with your voltmeter, it should read infinite ohms (open circuit). See what you find out.
Click to expand...
I will do so this afternon....

Few questions:

1.- How to disconnect the big red? do you simple remove the black rubber boot and unbolt...
2.- When yoy say "to ground" do you mean to the chasis, for example?
3.- If the voltmeter read infinite ohms, What does it means?
4.- What other options could the voltmeter read and what would it mean then?

Thnak you in advance
 
Disconnect the ground pole/cable from the battery before you do this or anything electrical.

1. Yes remove rubber and take the nut off and remove the wire from the alternator.
2 chassis yes. Or the metal case of the alternator. The case of the alternator should be grounded so they both should give you the same result.
3. Infinite resistance (ohms) means that the positive and the negative ( ground ) are not connected together which is what you want. You don’t want the negative and the positive connect that together…
4. Anything other than open circuit (infinite ohms) is not good. It could be zero or very close to zero.
 
Luis A. said:
Disconnect the ground pole/cable from the battery before you do this or anything electrical.

1. Yes remove rubber and take the nut off and remove the wire from the alternator.
2 chassis yes. Or the metal case of the alternator. The case of the alternator should be grounded so they both should give you the same result.
3. Infinite resistance (ohms) means that the positive and the negative ( ground ) are not connected together which is what you want. You don’t want the negative and the positive connect that together…
4. Anything other than open circuit (infinite ohms) is not good. It could be zero or very close to zero.
Click to expand...
Thank you @Luis A. ….

It seems to be an open circuit.

These are the pictures with the result of the test:

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Now what should I do? What could I try new?..

Thank you for Al your help guys

Regards
 
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