I have a problem with my alternator when i am at idle. when i am running the A/C and i come to a stop the voltage drops way down. when i start driving it moves back up, but it never goes back over the 13 mark. is there something i can do about the low voltage at idle? is it a alternator problem? thanks

Steve

 

Your alternator is too weak. I have the same problem. You'll need to get a high output alt.

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-Justin-
T-Top '86 5.0L LG4 700R4 WS6 Now Bilstein equipped!
T-Top '92 5.0L TBI 700R4
My '86 Firebird Homepage
The F-body Model Kit Pictoral Archive (updated 9/18/00)

There can be only one!!

 

i was thinking it might be a week alt. should i consider a 140 amp one?

 

You really have to look at ratings. Is the 140 amp rated hot or cold? Whats the output at idle? Is it rebuilt? What's the current alt's ratings? Things like that.

------------------
-Justin-
T-Top '86 5.0L LG4 700R4 WS6 Now Bilstein equipped!
T-Top '92 5.0L TBI 700R4
My '86 Firebird Homepage
The F-body Model Kit Pictoral Archive (updated 9/18/00)

There can be only one!!

[This message has been edited by Justins86bird (edited September 19, 2000).]

 

the current alt. is rated at 105 Amp. it is a delco remanufactured. but i will defenitly be looking into a higher output alt. thanks for the info

 

You can also try putting on a smaller alt pulley. This will spin the alt faster, so it will put out a bit more amps at idle. March sells one for about $30. Sorry, dont know the part number off hand. Might be worth a try, and for $30, it's cheaper then buying a new alt.

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-Justin-
T-Top '86 5.0L LG4 700R4 WS6 Now Bilstein equipped!
T-Top '92 5.0L TBI 700R4
My '86 Firebird Homepage
The F-body Model Kit Pictoral Archive (updated 9/18/00)

There can be only one!!

 

I recently learned that the diodes, usually 3 of them inside your alternator, on occasion will blow out, you may only be running on 1 or 2 diodes and that may be the reason for the low output. My only suggestion is to get a new high output alt.

 

Before you blame the alternator, take readings AT the alternator. Don't trust the stock gauge!

I got a Powermaster 140 amp alternator and the gauge still dipped below 13 at idle. At first I was pissed, but then I tested the alternator. It puts out 14.5 volts and 95 amps at idle! Yet in the car, at the ECM, for example - I only had about 12 volts! So I guess the original GM wiring sucks. I'm slowly rewiring my car top correct this problem. But DON'T TRUST THE GAUGE! At least put a voltmeter on the alt. and see what you REALLY have.

Jed
89 Formula 350

 

Yah, AutoZone and Checker will do it for free out here.