use2windsurf

'97 944 base
(all measurements with a volt meter)

My battery died a couple of times over a few days. The voltage would stay around 12 V or so when the car was running. When the car was off, the battery would drop quickly to around 11V and then to nothing. I was charging my AC and left the car idling and the car completely died in about 15 minutes or so. Took the battery and had it tested, was told it was bad so bought and installed a new one. Battery voltage when running jumped to 13.5V and when the engine was off the voltage was about 12.2 or so. I did notice if I started the car and idled, the voltage would sit around 12V and not seem to change. If I gave the accelerator a few light pumps the voltage would jump up to 13.5V and stay as if the alternator kicked in. What would cause the alternator to kick in when I pump the accelerator? No big deal replacing the alternator, but I have other pressing repairs to make and dont want to replace it if not necessary. Has anyone seen this?


thanks,

Dougs951S

Sounds like a slipping belt, check the tension. It needs to be fairly tight. If I read your post right, you had 11 volts when the car turned off, and then the battery drained while the car was turned off? That means you have something in the car that is draining the battery with the key out.

use2windsurf

I'll check the belt.

With the car idling the battery died and the car stalled, my thought was the alternator was not working at all, but then it seemed to work if I pumped the accelerator. Thx

mytrplseven

The belt should be tightenend so you can depress it 1/2 to 3/4 inch along the longest leg. When the voltage drops real low, the car will falter and eventually die. You could very well have a bad battery as well. I'd check the battery first and then after you've installed a "good" one, put a voltmeter on the batter terminals with the engine running and you should read over 13.5 volts. If you don't have that after intially starting the engine, rev it up over 2000 rpm and see if it has finally come up. If the volts still hasn't come up, I'd next suspect the voltage regulator on the back of the Alternator. All this with the belts tightened to proper tension, of course.

william_b_noble

your alternator is good, the battery was bad. depending on temperature, you will measure different voltages - the better test is to turn on headlights and see that the voltage doesn't drop

ilikemy944

This sounds to me like the voltage regulator. Thankfully a $18 part from Paragon, it is the 'fixable' part of the alternator.

use2windsurf

Thanks guys

use2windsurf

I replaced the V regulator this weekend and no joy... bushings were worn bad, but still acted the same. it seems to work ok in the mornings when it is cooler out but drops at least a volt when I drive during the day.. ordered a new alternator today.
regulator before and after.



1987 Garnet Red 944 N/A

azbanks

I just went through this same thing. It was a bad alternator for me as well.

mytrplseven

One of the things that is a common mis-conception with the VR is that when the contactors are worn down, so are the rings on the alternator. The new contactors don't ride or seat properly on worn rings, so this may well be why your new VR didn't work.

use2windsurf

Follow up, it was indeed a bad alternator. I bought a voltage regulator and it helped a little but would only work when the alternator was cold. turns out the races on the alternator rotor were prett worn and ate up the new regulator. I bought a nice used Bosch alternator from a respected eBay seller ($60 shipped) and it works great, charges at 14V.

1987 Garnet Red 944 N/A