hi all, i have a 1992 volvo 240 wagon m47. some history on this issue, it all started over a year ago when, when i replaced my engine mounts, i removed the alternator for easier access and when i put everything back together i forgot to tighten the alternator positive wire nut and the positive wire jumped around and melted the stud, i had the alternator tested and is good, i have tried a different alternator and same issue. my current issue is that once in a while when i start the car the dash lights stay on while the car is running, and the alternator is not charging and battery volts is 12.2v with engine running, but once i rev the engine the alternator starts charging normally, with battery volts at around 13.4v or if i release the parking brake before revving the engine the dash lights go off and alternator is charging fine. i have checked the wire under the engine and is good. also whenever i turn on the headlights the engine bogs down a little or when i use anything electrical.
any thoughts or suggestions?

 

start by checking battery connections at the terminals then check the ground strap to chassis connection. Next check the positive cable for any swelling / bubbles on the insulation. Next clean the connectors to the alternator wires. If the engine bogs down when you put a load on the electrical system, I'd be thinking it's time for a new alternator since it sounds like it can't produce enough amps. Also, 13.4 V with the engine running is barely enough to charge the battery - I'd expect 14V+ with no load and maybe high 13s with a bunch of accessories. So try this - engine off, measure battery voltage. Should be 12.6- 12.8 for a 80%+ charged battery. If its 12.2 with the car off, your battery is weak and should be replaced. Now start the car and check voltage with no accessories/lights etc. Measure the voltage. Should be 14+ V. Next turn on the high beams, rear defogger, AC blower. Measure voltage - should be 13.5+. If this is below 13 then your alternator isn't producing enough amps.

 

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I found out that the voltage regulator brushes are very worn down and uneven.

would this cause my issue?

 

Certainly worn brushes will cause charging problems. It doesn't explain why a replacement alternator didn't solve your problem though nor does it explain the dash light problems, etc. Since they are worn go ahead and replace them.

 

I rebuilt the alternator and installed a good used regulator with good brushes and now it charges to 14.2V-14.3V.

 

I'd expect 14V+ with no load and maybe high 13s with a bunch of accessories. So try this - engine off, measure battery voltage. Should be 12.6- 12.8 for a 80%+ charged battery. If its 12.2 with the car off, your battery is weak and should be replaced. Now start the car and check voltage with no accessories/lights etc. Measure the voltage. Should be 14+ V. Next turn on the high beams, rear defogger, AC blower. Measure voltage - should be 13.5+. If this is below 13 then your alternator isn't producing enough amps.

 

I rechecked the voltage again and the alternator is charging to 14.4v and with headlights on the battery is at 14.1v. My car no longer has A/C.

 

Enough current to melt the alternator stud would have to come from the battery. Sounds like a possible short in the alternator. It may be an intermittent fault to not show up when the alternator was tested.