QuestionI have a 1986 Porsche 944. A few months ago my ac compressor froze up and snaped the belt, and ever since it has happened every time I turn my headlights on the belt will start to squeel and the battery power will drop. It stops squeeling once i reach high fourth gear. I haven't replaced the ac compressor yet, I have replaced the belt. What do you think could be the problem? And how would I go about fixing it?
AnswerHi Chris, I guess in this case I need to ask a couple more questions first, before we can get on with correcting your problem. Let's see if I understand the situation:
When you said the "ac compressor froze up and snaped the belt", I'm unclear. The belt driven a/c pulley normally spins freely and the belt moves the pulley as fast as it likes. When the a/c is turned on the clutch mechanism in the pulley is activated, the compressor immediately springs to action, and (normally) the pulley continues to spin in time with the belt's action. No problem here.
When the belt was snapped it would typically be caused by the compressor's having frozen up from disuse or age...and when the clutch was activated the pulley would STOP. Then the belt would be toast, as you've seen. Usually, if this occurs, any new belt would also be toast on re-start-up, because once frozen, the a/c compressor pulley won't turn...are you saying that after you replaced the belt, the a/c compressor pulley spins freely just as if you'd never broken the first belt? When the car is at idle, the belt drives the a/c compressor pulley and it is completely silent?
And the belt and the a/c compressor continue to run as normal, silently, until your headlights are turned on? A squealing noise follows immediately, along with the battery voltage meter moving to a lower range? The squealing stops when you reach 100 mph (or some high rate of speed in 4th gear)?
Please write back to me if you need to clarify my understanding on any of the above.
In the meantime, if the a/c pulley is running silently, it sounds like the a/c compressor issue is actually irrelevant...focus your attention on the alternator/generator. It's belt (oh yeah, the very same belt you just replaced) is too loose. The tension on the belt needs to be adjusted a bit more.
What I just said doesn't make any sense, because: When the headlights are turned on the regulator tells the alternator/generator that it has to supply more voltage to meet the increased demand of the headlights...and those headlight doors mechanisms. Battery voltage meter then tanks. More strain on the alternator...but this activity should be silent. When the alternator voltage rate matches the demand, somewhere (coincidently) about the same time you're reaching 100 mph...the voltage meter should look better...but all this should be silent too.
There's no extra strain on the alternator pulley by the alternator when the alternator is under increased demand...so something sounds wierd...but try adjusting the belt tension a bit more...and write back to me to let me know what you find out.
Dave
PS. The other likelihood is that the belt is really loose, the a/c pulley really is frozen, the belt slips around it at idle, at all speeds, the pulley doesn't ever turn and it squeals (coincidentally) around it whenever you turn on the headlights...and all this could be fixed with a non-frozen a/c compressor. You'll have to figure this out and give me some feedback. Thanks.
