Electrical charging system question, Alternator? |
|
Porsche, and the Porsche crest are registered trademarks of Dr. Ing. h.c. F. Porsche AG.
This site is not affiliated with Porsche in any way. Its only purpose is to provide an online forum for car enthusiasts. All other trademarks are property of their respective owners. |
|
Electrical charging system question, Alternator? |
rjames |
Jun 10 2006, 04:11 PM
Post
#1
|
I'm made of metal Group: Members Posts: 4,111 Joined: 24-July 05 From: Shoreline, WA Member No.: 4,467 Region Association: Pacific Northwest |
I installed a brand new battery and a new voltage regulater last week in the car. My volt meter is showing 12.5 volts at the terminals. With the car running and the lights and fan on my volt meter fluctuates between 12.7 and 12.9, then slowly starts to dip, getting as low as 12.5 before I decided to shut the engine off because I could see that the battery was slowly draining.
Would it be logical that the alternator might need replacing? The alt. belt also seemed tight (not sure exactly how tight it should feel though.) I can check the electrical connections (have to find them first though.) The connections at the battery all look good though. It doesn't look like a fun job to replace the alternator, but I'm up for the challenge. Anything else I should look for before I go this route?? Thanks! PS: Forgot to add that the alternator light on the dash comes on when starting the car, but goes off right away once it's started and doesn't come back on at all when driving. |
rjames |
Jun 27 2006, 11:44 AM
Post
#2
|
I'm made of metal Group: Members Posts: 4,111 Joined: 24-July 05 From: Shoreline, WA Member No.: 4,467 Region Association: Pacific Northwest |
QUOTE I had the identical symptom a long time ago. Kept driving for over a year, but I tried to run with the headlights off for a while to top off the battery before shutting down. Anyway, I tried everything you've tried, and finally pulled the alternator. It had a bad diode. Apparently, when it was cold, it operated more-or-less OK, but as it heated up the reverse-bias current leakage increased and one of the phases of the alternator contributed less and less to the total power output of the alternator. Eventually, the diode failed completely. A failed bridge rectifer will decrease the total power output for the alternator by a third? I think. So under light load, it could regulate to a higher voltage, but it dropped with load. When it failed entirely, it was only delivering about 10.5 volts under load, though still almost 13 volts with everything turned off. So that's one more input to think about.... In my own car, I now have the voltmeter connected directly to the + battery terminal, through a relay that drops out when the ignition is off, so I get a pretty good indication of actual charging voltage. Between high load- headlights, fogs, and front blower- and minimum load, I only see about a 0.3 volt difference, with the lowest being about 13.3. I'm also using a NAPA solid state regulator... Hmmm thanks for this posting jk76. I will start with the sollid state VRegulator first as that's an easy one, but may just try pulling the alternator. Not being electrically enclined I'd be interested in knowing just how to wire the volt meter the same way you did so I could get accurate readings. If you're able, I'd love a step-by-step on how to do this- keeping in mind I'm a novice at electrical stuff. |
Lo-Fi Version | Time is now: 27th September 2024 - 10:07 AM |
All rights reserved 914World.com © since 2002 |
914World.com is the fastest growing online 914 community! We have it all, classifieds, events, forums, vendors, parts, autocross, racing, technical articles, events calendar, newsletter, restoration, gallery, archives, history and more for your Porsche 914 ... |