Im getting an odd, intermitent weak charge condition. I replaced the alternator about a month ago due to it being totally shot (210k mi, no charge)
And figured rather than open it up to replace parts, I can get the Alt. cheap enough through a friend, and it has a lifetime warranty.

Using the aftermarket digital volt gauge that I hooked up, while at idle at a light, Im getting maybe 12.7v. On the highway, it sometimes goes up to 14.v or so, and then drops back down to 12.7ish. Increasing the electrical load by turning on headlights, and A/C causes it to periodically drop to 12.3 and stay there for a while, then jumps back up to 12.7.

Turn the stereo on, and start a bass heavy song, and it drops into the 11.9-12.0 range, unless I bring up the RPMS, at which point the highest Ive noticed it going was 12.5v.

Keeping in mind that there is no Alt/Charge Light on at any time during this, and I have confirmed the low charge with a charge tester at a local shop.

Something is totally bizarre here. Does the charging system run through the ECM like it does on a bunch of chryslers and other cars? How can I jump that out of the system to test it, if so.

Should I just Yank the Alt and take it in to be bench tested, and maybe for spite replace it under warranty? GRRRr... Frustrated.

 

Loose alternator belt?
Bad alternator?
Blown fuse 15 under the dash?

 

New belt, and its tight
New Alternator (yes i know, new doesnt neccissarily mean good)
and if it was fuse 15, it wouldnt be intermitent, would it ?

For the sake of knowledge, which one is #15? The lid/map of the fuse box has been gone since be4 i got the car. And there was of course, no owners manual. I DID DL a pdf of the service manual, but that thing is so difficult to get to the right section that it causes even more frustration.

 

7.5A dash fuse #15:




If the fuse is fine, get a replacement alternator.

 

ok, fuse is fine.

As per the manual, there is an Elec Load Detector Module either in, or attached to the ECM.... Could be a likely cause? maybe?

If i can find the darn testing diagram for it, Id be able to jump it out, but i cant find the correct page # anymore.

 

And... THank you for the info Ronj

 

The ECU can command the alternator to drop to a lower voltage (which I think is 12.6 volts, it should never go below 12 except possibly with a heavy load at idle rpm). The ELD input is used to compensate idle speed by anticipating a heavy load. I don't know when the dropout output is activated but I think it is very rare. Under normal cruising rpm (not WOT) with stock electrical loads only, you should have a very solid 14 volts. I agree (assuming fuse 15 is OK, which applies power to the alternator's I wire with the key on) the most logical explanation is that your bargain new alternator is a dud.

 

Thanks mk378.... pretty much the conclusion my diag came to too. grr....well, at least its not gonna have a siezed pivot bolt this time lol