Charging issues

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Dec 17, 2011 | 01:55 PM

idaho86f150

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Charging issues

So I have been having some issues. Here is what has been done so far:
~Two new battery's. The old ones were getting weak.
~New Alternator.
~Did a voltage test and at idle I was getting 12V. Let it sit and run for awhile and it dropped down to 11.95V

~I took the connector off the alternator and with the key off, one of the terminals has power, and when the key is turned on the other terminal gets power.

If I rev the engine up to 2000RPM I can get a voltage reading of 13.2V. So the power is traveling from the alternator to the battery. The readings off the alternator are also the same as the ones from the battery.

Any ideas/suggestions?

Dec 17, 2011 | 10:21 PM

99f350sd

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From: Lyndonville, Vermont

What truck and year? battery charging voltage should be above 14v with charged batteries..14.4 usually unless the batteries are really run down. Sounds to me that the alt is bad or some wireing issue.

Dec 17, 2011 | 10:33 PM

twags6

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From: Slatington, PA

I'm guessing by the fact that you replaced both that you have a diesel. What brand alternator did you put in? The remans and even some new ones are known to have DOA parts right out of the box. Could be that the voltage regulator is shot already. Another thing to check is that there are no fuses blown. My truck has one 10 amp mini fuse under the hood. Yours should have one somewhere.

EDIT: Is this the 99 F350 7.3L PSD you've posted about in other threads? I'd check to make sure that plug on the alt is snug. Even try wiggling it around while its plugged in. They get loose after a while and poor contact could be the issue too.

Dec 19, 2011 | 12:07 PM

idaho86f150

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Sorry for the late response.

Yes it's a '99 F350. 7.3.

How long should the glow plug relay stay hot? I started it up yesterday and after running for 10 minutes or so there was still power going through relay.

I thought they were supposed to shut off after the first two minutes or so?

The alternator is a NAPA reman. I had them test it before I went out the door and everything came up good. For what that's worth.

All the battery cables got cleaned and the alternator wire terminal got cleaned.

Dec 19, 2011 | 12:53 PM

idaho86f150

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I just went out and tested the GPR.

With the key on, and my tester hooked to the two small terminals I am getting 12V.

But with the key on I am not getting 12V to the hot side.

Dec 19, 2011 | 01:14 PM

idaho86f150

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Okay final update.

I think the Glow plug relay was the culprit.

I believe it was stuck open, causing a major amp draw etc etc. And then it must have finally burned out because now I am getting zero volts through it.

And my alternator is now showing 14.4 volts

Dec 19, 2011 | 01:15 PM

twags6

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From: Slatington, PA

Both of the small terminals will show around 12v because the PCM grounds the one lead instead of powering it. The large terminal with the black/orange wire should be hot all the time and the one with the brown and yellow wires should be hot for 0-120 seconds depending on the outside air temp and oil temp. Are you saying that neither large terminal has voltage? If thats the case, either a wire is loose or a fuseable link blew in the black/orange wire, which also happens to be the same wire that the alternator charges the truck with.