Low Voltage Output from Charging System

CrossT · 11-20-2006, 03:39 PM

I've been having a dead battery issue w/my 86 and just had a new batt installed today, cuz the previous tested out as bad. The Sears guy who put the new batt in said the charging system should be looked at cuz it was only putting out 11v, where it ought to be near 14v. Is a low voltage situation like this likely due to a regulator or an alternator?

thx
todd
86 coupe

Early_S_Man · 11-20-2006, 03:51 PM

Todd,

The alternator has to come out in your case no matter what the problem.

With all of the '82 thru '89 models ... alternator has an integral regulator mounted where just the brushes used to reside. The Valeo and Paris-Rhone alternators used from '82 thru '89 have been the least reliable alternators every fitted to a Porsche model! It is said that excess heat causes Voltage regulator failures in the alternators with integrated regulator.

I suggest pulling the alternator, then have it tested at an alternator shop.

john walker's workshop · 11-20-2006, 03:58 PM

then that was a sears guy......

Early_S_Man · 11-20-2006, 04:02 PM

... or Wal-Mart guy!

CrossT · 11-20-2006, 04:11 PM

ok . . . Well at least the SEARS GUY had the sense to write down on the ticket to 'take to specialist, voltage output too low' vs. suggesting to me that they fix it.

todd
86 coupe

stevej37 · 11-20-2006, 04:44 PM

When I had the same problem with the alternator in my 84, I removed it and took it to three diff auto parts stores that advertised "alternator testing" None of them could test it because the fixture that they use to hold the alternator down would not work because of having no through bolts. Maybe a specialized alternator shop would have one.

EnlightenedOne · 11-20-2006, 04:51 PM

If your not going to or can't diag car your self, best bet would be to take to a porsche shop for diag. could be just loose or bad connection behind the alt.

911pcars · 11-20-2006, 04:59 PM

Find a good electrical shop to test it on the car. They usually know more than the average dealer ..... and without the Porsche tax.

Sherwood

CrossT · 11-21-2006, 07:55 AM

Thanks guys, I will hook up my multi-meter to confirm the low charge note, and take to a shop for work. My talent/knowledge is minimal and my time is nil.

todd
86 coupe

CrossT · 11-22-2006, 04:15 PM

Hooked up my meter and found that my trusty Sears guy was a little off

Car off, it was reading 12.3; at idle it was reading about 12.7v and at about 2k, it was reading about 13.4 and after about a minute was slowly still rising. Maybe ok? I had nothing running. Seems 13.4 is a little low, but it may have risen another few 10ths.

todd
86 coupe

304065 · 05:55 AM

Bad battery. 12.3V = 25% charge. The alternator is working as hard as it can to bring that back to 12.6V.

Charge the battery for THREE DAYS using a modern "chipped" battery maintainer such as the Battery Tender. Repeat diagnosis with car off and engine running. This will tell you if the VR is working right.