Whatís the furthest that youíve ever driven in a car that is solely relying on the battery? Anytime that Iíve had an alternator not charging the battery (bad charging system) I never made it very far.
The OP has indicated "Just now had alternator & battery checked. He said that was fine". IMO we should assume that the alternator is putting out something (IE not totally dead).
To you point, I agree. IF the alternator were totally dead, the symptoms and results would be obvious. In that the car would quit running after a relatively short period of time.
I could easily see a case where a weak/low output alternator would pass a quick bay test but fail a high load test. Especially if the mechanic is not looking for a high load related "issue".
I have helped several people that have replaced TONS of cooling system related parts in an effort to fix an "apparent" overheating problem that in the end turned out to be electrical in nature. For an example of a "possible theory" in this case:
- Weak Alternator is not able to fully cover it's rated output for what ever reason.
- Cooling fan kicks on requiring HIGH power draw.
- Alternator isn't able to keep up. Battery has to help cover load.
- Battery voltage drops as high speed cooling fan runs. This causes the temperature gauge to read high.
- Motor temperature eventually comes down. Cooling fan shuts off. Alternator is now able to met lower demand.
- Battery begins to recharge.
- Wash, rinse, repeat.
Effective automotive repair is a data driven process. Do we know that a through and complete test of the charging system has been done? Or was the limit of the test, the alternator has to be good because it's charging the battery in the service bay?
This problem may indeed turn out to be T-stat or other hard cooling part related. However, I stand by my original recommendation. Perform a THROUGH
review of the battery and charging system BEFORE