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86 911 Targa 86 911 Targa is offline
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Join Date: Jun 2009
Location: Manhattan Beach, California. Factory Delivery-Original owner-Retired engineer
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Quote:
Originally Posted by chamilun View Post
Well, it appears that if voltage drops considerably with "electrical components" all turned on, you have a bad alternator. I guess the ac kicking on simulates this scenario.

I want to make sure before I replace the alternator that a short is not a possibilty. The low (<13.5) output tells me it has a bad diode(s)
Typically, if the VR diodes fail, the voltage goes high, and the battery get's cooked.

A lower voltage is most likely is the alternator.

Bentley's has a good chapter on this subject.

Have you tested the battery's specific gravity?.

Load test?.

V-Belt?.

Also, if possible, can you record the battery voltage, disconnect the battery overnight and re-measure the voltage in the am?.

The are several troubleshooting step you can take before "surgery".

Our alternator was completely rebuilt about 5K miles ago.

R&R(ing) the alternator was about a two hour job.

I'll take measurements tomorrow (static, running, running W/ A/C and lights,

and pm you.

Cheers,

Gerry
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Last edited by 86 911 Targa; 08-29-2009 at 02:46 PM..
Old 08-29-2009, 02:42 PM
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