Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[Blartiartfast]

Hi, I know its my 1st post, etc but I ask the following for a good friend who is having an issue with his car.. Muggins has been asked to sort the problem for him.

 He has recently had a new alternator fitted. The harness gets warm to very warm when the lights, are switched on (basically when there is a decent load). The battery will discharges under these conditions.

 If everything is switched off and the car is driven for a while then the loom is just slightly warmer than you would expect it to be..the battery wont charge, but doesn't discharge..

 I'm guessing either the monkey that fitted the alternator has wired it incorrectly, or the reg/rec is faulty..

 Any help please. He's asked me to help resolve the issue because I am the only person he knows that "knows about this sort of thing".

 I'm an electronic engineer by trade therefore " must know whats up with it".. TBH I hate car electrics, and hats off to the guys that have learnt the system.. Horses for courses is what I say, but I did agree to help him.

 Any help please?

[Ghost]

If the battery wont charge then check the relays for it first, it does dound as if it is wired up wrong though,
is it an omega (mig) or another car?

[Kevin Wood]

Whereabouts is the loom getting hot? If it's by one of the battery terminals it's a classic problem of the wire becoming loose in the crimp and resistance increasing. Solution is to replace the battery terminal with a screw-on one from Halfrauds or similar.

If it's getting hot somewhere else it points to high resistance there, or an overloaded circuit.

Kevin

[LFF64]

Is the battery any good   :question

[mathewst]

Battery will discharge even if everything is off (something must provide power to spark plugs and fuel pump sidelights etc..) only it will take longer to discharge.

[Blartiartfast]

Wish I'd got an Omega now.. You lot are more helpful than the Ford lot I use for my car (arf).

 Yes the car is a MIG.

Yes, just rang him and he says that its the red wire from the alternator that is getting hot, to the point where he now has a blister on his finger (different from what he said last night and to what I initially posted).

 Not seen it yet, but I am assuming that the red "heaviest" wire from the alternator connects directly to the battery. From the heat generated think its more short circuit now rather than high resistance.. Sound right, or am I barking up the wrong tree..

 Sorry for sounding like a noob, but I've not been out to the car yet to measure anything. Give me a mobile phone, or a TETRA system to play with and I'm at home.

 Thanks again for the help offered, and any further thats offered.

[Kevin Wood]

he says that its the red wire from the alternator that is getting hot

Is this wire getting hot along the whole length or just near the battery terminal? These do get very hot if the terminal is poorly crimped IME. You have up to 100 amps of running load plus charge to the battery so the slightest bit of resistance generates a lot of heat.

Kevin (17 years in GSM T&M development)

[Blartiartfast]

Great stuff. Now I see why I stick to < 2 amps.

 Just rang him again, and he did say that the battery end was the end that burnt him, but the cable was very warm further down the lead (which sounds normal giving the heat generated at the one end). He didnt follow the lead any further as he'd already been burnt and didn't fancy another. Whimp.

 Me and my trusty Fluke 123 meter will go and have a butchers. Thankyou very much for your time.
 Dave.

[Kevin Wood]

Sometimes you can measure the voltage drop between the battery terminal and the exposed copper conductors of the wire.

Also, copper is a good conductor of heat, so heat generated at the battery terminal will be conducted along the wire.

I'm confident that this will be your problem. Grasp the wire as it emerges from the battery terminal and I get you will be able to twist it inside the crimped area whereas this should be firm.

Get a new battery terminal, trim off any damaged cable and re-make the connection.

Kevin

[Blartiartfast]

Cheers for that. Looking into that now.
 There is an oddity though.
Battery reads 12.5v start the car, 14.5v is now read. Rev the car at any range and the voltage remains the same. If lights, heated screens, etc are turned on then the voltage drops to around 11v with the engine running.

 Recramping the terminal in a moment, but could their still be anything else?
 Thankyou

[Kevin Wood]

Cheers for that. Looking into that now.
 There is an oddity though.
Battery reads 12.5v start the car, 14.5v is now read. Rev the car at any range and the voltage remains the same. If lights, heated screens, etc are turned on then the voltage drops to around 11v with the engine running.

 Recramping the terminal in a moment, but could their still be anything else?
 Thankyou

Nope. Still sounds like the same issue.

All the load for the car and battery charging goes through this connection, so, with the battery having recovered its' charge the alternator can drag it up to the proper voltage. Put some load on and the resistance causes voltage drop.

I'm surprised it went down to 11 volts, though. Makes me wonder if the battery is OK.  :-/

Once the crimp is repaired  try the checks in this HOWTO: http://www.omegaowners.com/forum/YaBB.pl?num=1225724099


Kevin