Is it possible for an alternator to function as expected but after it heats up or maybe even overheats it starts to fail? Then after it cools down (20 to 30 minutes) it functions as expected again until the breaking temperature is reached.

If this could be a thing what would the symptoms likely be? Could it be loss of power? Rough Idle?

 

It can happen but it should only cause the charge light to come on. The engine should run fine on just battery if it's close to full charge. Unless the alternator is overcharging. That might cause problems, but not like what you describe.

Your best diagnostic tool would be a volt meter. Measure voltage cold, and measure voltage when the problem happens. You can get a cheap meter at Harbor Freight.

Doesn't sound like an alternator problem though. Why did you choose that?

p.s. vehicle type and year would help.

 

The short answer to this is YES.

You could have a broken wire or a loose connection within the alternator, when it get hot the wire will expand and increase the gap causing a non-operational condition, when it cools off the wire contracts and the connection is re-established.

 

Why don't you just tell us what your symptoms are?


Typically you won't have loss of power or rough idle from an alternator. Except right before the battery dies and won't keep the car running anymore. When the alternator is not working it actually will run off the battery until the battery goes dead.

If at night and you need headlights you're screwed. In the daytime you turn off the AC/fan....no radio... Nothing that draws power besides the ignition.. And you can drive 100 miles that way.

 

Originally posted in "Strange occurrence A/C and Miss"

After my truck warms up it develops a miss. Here are some of the facts that go with it.
1) Only happens when it is 85 degrees or greater outside.
2) May or may not happen if AC is off, but will most likely happen if its over 100 (I live in Vegas so that's a cool day in summer)
3) If I turn the AC on then you can almost time it with a watch, 1 or 2 stop lights or maybe 15 minuets it will start to miss.
4) It will not correct itself unless the truck sits for 15 to 20 min.
5) Originally I had a P0355 "Ignition Coil E Primary Control Circuit/Open" code.
- I would clear it, swap Coil pack 1 with 5. code would return same #5
- Cleared it and swapped spark plugs. Code returned #5
- Cleared it and drove small distances until I could pass smog.
6) I had an instance when I was driving up a hill (when it was cool out) and I lost power, had a hard time getting past 45. that has not happened again.
7) I am not getting any codes since i passed smog so its hard to tell if its still #5.

Because the issue seems to be based on a miss (probably electrical) and turning the AC on should not cause this, I'm thinking maybe when its hot out the alternator gets warmer than it does in winter and when I turn the AC on it adds more load to it and heat causing the issues to happen quickly. That's the logic behind the alternator question.

I think I will induce the issue check the voltage like suggested, and then let it run until an engine code gets thrown. I did have the later checked during normal operations and it was fine.

 

The computer has a Coil driver that supplies a ground to the coil.
When the driver opens the ground, the coil fires the plug gap.
The program monitors the driver to coil circuit path for a Current signature.
If it is missing, the coil circuit is going open and sets the code for that cylinder.
It can be heat related any where along the path.
It can be a failing coil driver in the computer.
The connector at the computer, the harness at the connector plugup, the coil connector.
Use your trouble shoot time looking for a reason the circuit goes open from heat expansion.
Good luck.