Only getting 12 volts from alternator at the battery

[turboost]

I put on a new alternator and battery, both have been tested to be good, and I am still not getting a full charge. I replaced the power wire from the back of the alternator to the battery, checked the grounds on the engine and still can not get 12 volts when the car is running. It slowly keeps dropping from about 12 with a freshly charged battery.

I have a RA volt booster on now and I have taken it off and tried it w/o it with the stock connector. Does anybody have any suggestions as to what could be causing this.... a loose ground, a short somewhere, a bad wire? Any help would be appreciated, thanks.

 

[Quick6'n'-K.C.]

is it always only 12v??

hmmm- what kind of multimeter? or are you reading off your scanmaster?{ difference}

possible that the positive wire is grounding to the header or the frame?

 

[turboost]

I'm getting my reading using a multimeter showing only 12 volts from the alternator and I am using my scanmaster to watch my volts drop as I drive it. I am also getting a code 23 which has to do with the MAT sensor. If this is bad could it cause a problem like this (maybe an open circuit)?

BTW I followed all the wires running from the battery and alternator and none are cut or grounding (except the negative wire)

 

[Swt_86]

Probably not the problem but...

When you put the new alternator on, are you sure you hooked up ALL of the wires? Long story, but Mr. Goodwrench screwed up the installation of my alternator about 13 years ago & I recently had to take it apart to fix the hot wire connection post. Really hate to admit it, but when I put it back on, I totally had my head up and locked. Forgot to plug in the two wire connector which caused the same thing you have - until I plugged it back in.

 

[sam87]

Is your battery fully charged?

From what you've said, the battery sounds suspect. Try charging it with a battery charger (not the alternator) to see if it will actually get fully charged. A fully charged battery should read more than 12v - at least 12.6v according to literature. I've had them read almost 14v. My experience is that batteries that read just 12.0v are either bad or going bad soon.

 

[JFH]

Make sure the idiot volt light in the dash is working. If the bulb is burn't out it will not charge.

John

 

[turboost]

When the battery is fully charged it reads 12.1 on the scanmaster. Is the idiot light the "low volt" light in the dash? I haven't seen it come on this whole time. If it is burnt out it could cause this problem? How?

 

[captrob]

That wire(brown)...

is the energizer for the field. If the volt light does not come on, key on, then the alt will not charge. Check bulb first, if good check wiring. Some cars came with a bulb that had a resister(I think) attached to it, in case the bulb burned out. My 86 T had one, the 87 GN doesn't.
I would think yours doesn't, so it needs a good bulb. Sometimes the connectors don't make good contact with the back of the instrument panel, check this too.
HTH, CaptRob

 

[Russ Merritt]

I also ran into this problem on a car, it turned out to be the boost a pump wasn't working right and drawing all the juice. Check everything you have hooked up, all accesories.

 

[TurboDave]

Originally posted by JFH
Make sure the idiot volt light in the dash is working. If the bulb is burn't out it will not charge.

John

What John said!!

 

[turboost]

I would like to say THANK YOU for all the help. It turned out to be a burnt out idiot light. You don't know how big of a relief it is.