I just lost my alternator, when I pulled it out the ground strap was melted. What would cause this? Did it short out somehow? I can't understand what would cause the alternator to do this. Should I try to have it rebuilt at a local shop or replace it. Advance auto has one for $129. eeuroparts wants a lot more.
I just lost my alternator, when I pulled it out the ground strap was melted. What would cause this? Did it short out somehow? I can't understand what would cause the alternator to do this. Should I try to have it rebuilt at a local shop or replace it. Advance auto has one for $129. eeuroparts wants a lot more.
perfect time to upgrade to the 9000 higher amperage alt.; thats what i would do; source a good known used one on ebay and change the pulley and brushes, bin the one you have now, and dont waste time trying to figure out whats wrong with it..
In normal operation this shouldn't happen, investigate the cause before replacement. There must be a short somewhere or maybe the engine earth strap has gone and the alternator earth was overloaded?
I took the alternator to a local auto electric shop. He said the alternator was fine, but that the ground strap was melted. He told me to check the battery ground. I just can't understand how the ground strap could have melted. I don't see how the alternator could complete a circut to ground with enough amperage to fry the ground strap. The only thing I can think of is maybe one end of the strap became coroded and resistance built up causing it to get hot, but this is a bit of a leap.
It could have just become broken off at one end and the arcing from 'shorting' against another grounded part of the car or engine could easily create enough heat to make the copper heat up and the insulation melt and burn, especially when outputting a lot of current to run headlights, etc.
There is no way that the ground connection between the alternator and the engine could become the main earth path (and thereby replace the main ground cable between the chassis (behind the radiator) and the battery negative terminal. It doesn't take much current to flow when a connection is intermittent and arcing to generate a LOT of heat due to the high resistance at the point of the intermittent connection.
I started the second thread because I found out the alternator was NOT fried, but rather the wire grounding it was. I thought it would make more sense to have a thread about the real problem. I am having a hard time seeing how that wire got cooked. The only thing I can think of is that it became torn or weak, generating more resistance and got hot enough to melt.
I think you are probably close to the truth there. When you replace it it would be good insurance to solder the crimp terminations and make sure the cable terminals are clean too. Just so you've got no stray resistance anywhere.
I have a new 8 ga. copper wire and have soldered an eye to each end. I have put heat shrink on each cover, and will assemble with dielectric grease. I am waiting for new mounting bushings before I put it all back together. I am still not comfortable with my reasoning that the wire failed due to poor condition, but cannot think of any other reason for the wire to melt.
In my C900's, the alternator to engine ground wires have usually been conncted under one of the bolts mounting the alternator bracket to the engine. This is where the wires always seem to fail as the movement of the alternator creates oscillations in the wire and the lug fixed to the engine doesn't move, so the wire breaks off where it goes into the back of the lug, both from vibration and corrosion of the copper strands over time.
WHen I renewed this wire in my 89 900i (16 v car) I make up a new wire using two sections of salvaged ground wire out of a harness from a car I'd stripped and the end attached to the engine is bolted under one of the fuel rail mount brackets (I have removed A/C so there's no compressor in the way to worry about) and both wires terminate in a single 6 mm ID crimp lug at each end so the lugs and the wire itself is quite heavy-duty.
Craig.
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