Alternators burning out

[frplymstr]

Hi all, my mate was given a VY 2004 3.8 Commodore when his mate passed. It had not been driven for years but he got the work done to pass rego. The Alternator that was in it burnt out aftsr he started driving it. It was not dirty, oily or even looked worn, but the copper wires had all turned black & smoke came out of it after short trips. I bought a brand new alternator for him & fitted it but even the new one gets so hot after short trips the copper wires are already turning black & you cant put your hand on it after any trips it is so hot. All the pulleys seem to be in good working order, we put a new serpentine belt on as a precaution. There is a fault regarding the ABS on the dash which we have assumed relates to the ABS module which has not been replaced yet. The fans were not working so we bypassed the temp sensor for the time being so the fans are running constantly while the engine is running, which we were hoping would help the Alternator temp but this has done nothing. Has anyone else had a similar issue or have any other sugestions as to why it gets so hot & burns out?

 

[shane_3800]

Hi all, my mate was given a VY 2004 3.8 Commodore when his mate passed. It had not been driven for years but he got the work done to pass rego. The Alternator that was in it burnt out aftsr he started driving it. It was not dirty, oily or even looked worn, but the copper wires had all turned black & smoke came out of it after short trips. I bought a brand new alternator for him & fitted it but even the new one gets so hot after short trips the copper wires are already turning black & you cant put your hand on it after any trips it is so hot. All the pulleys seem to be in good working order, we put a new serpentine belt on as a precaution. There is a fault regarding the ABS on the dash which we have assumed relates to the ABS module which has not been replaced yet. The fans were not working so we bypassed the temp sensor for the time being so the fans are running constantly while the engine is running, which we were hoping would help the Alternator temp but this has done nothing. Has anyone else had a similar issue or have any other sugestions as to why it gets so hot & burns out?

You need a new alternator wire, the resistance is too high.
If you have the tools you can do it your self, or you can take it to an auto electrician.

I usually upgrade them to a thicker wire, then do the battery terminals at the same time, also check the earths as they might need to be redone too.

 

[lout]

have your battery tested as you may be trying to charge a sulphated battery
is the replacement alternator quality or cheap ebay rubbish
if there is a short in the ABS pump it may be drawing a lot of current all the time. there is another connector under the abs module which is hard to see
also the fans draw a lot of current which places a large load on the alternator
i think you have a lot of issues going on, which are placing too much load on alternator

 

[frplymstr]

Thanks guys. He put a brand new battery in & it’s a Bosch alternator from Bursons. We checked the output of the alternator & then checked the Amperage draw on the battery. The draw was sitting around 6 amps while idling. We took the grounds off & cleaned them all up. We even disconnected the ABS connector to see if that may be causing the issue but same problem. You can literally see the copper wires blackening after a drive. Is there a way to test the resistance on the cables?

 

[lout]

the fans are probably drawing 40amps if both on constantly
did you disconnect the small wires or the power plug hidden under abs pump

 

[Immortality]

Measured the voltage output on the back of the alternator? Measure the voltage drop between the battery and the alternator?

 

[frplymstr]

The main plug at the front. I will look at the car again tomorrow to find the plug underneath it & check the actual voltage drop. Thanks again guys

 

[frplymstr]

Ok, the main cable coming out of the alternator that then splits & goes to the starter motor & battery, at the alternator side at idle with both fans running is putting out between 38-40 Amps. This cable at the battery is then sitting at 20 Amps. I also had the radio on. No other accessories were on. I can pull an engine apart & rebuild it but can’t get my head around electricals except for basics so excuse my ignorance. This would then mean I have a resistance of 20 Amps or is this just the basic draw from what was running? The only other device that this wire looked like it was running to was the starter motor which had disengaged by the time I took this reading

 

[shane_3800]

Ok, the main cable coming out of the alternator that then splits & goes to the starter motor & battery, at the alternator side at idle with both fans running is putting out between 38-40 Amps. This cable at the battery is then sitting at 20 Amps. I also had the radio on. No other accessories were on. I can pull an engine apart & rebuild it but can’t get my head around electricals except for basics so excuse my ignorance. This would then mean I have a resistance of 20 Amps or is this just the basic draw from what was running? The only other device that this wire looked like it was running to was the starter motor which had disengaged by the time I took this reading

I don't know how you're measuring this, but you need to take a voltage measurement between the alternator and battery and then check across the battery terminals, This will give you the voltage drop measurement.

 

[Immortality]

Fairly sure the cable splits from the back of the alternator going to the battery and the main fuse panel.