Why are volts low?

[SuperStang83]

My buddy called me this morning and told me that his Mustang left him sit, so I went and picked him up. After figuring out that it was the battery or alternator, we took both out of my Mustang and put them in his to be able to make it home. We stopped at AutoZone to see if his alternator was bad, and it was so they replaced it, as it was only 3 months old. We put it in quick and he said his volts were low on the way home. Then we tried putting his battery back in, but it wouldn't hold a charge, so we took that to AutoZone to replace it, and that was only 3 months old as well. We get home and put the new battery in and his volts are still low and he only ran it for about 5 mintues and the gauge keeps getting lower. The only thing that I can think of is that we changed his belt last night, because the belt that was on it didn't go around the smog pump, and we got a longer one to go around that too because he has an emissions test coming up. The previous belt was going around the fan pulley the wrond way and we put the belt on the wasy the Ford diagram shows how to on the core support. Does anyone have any ideas what might be going on that the gauge is sitting lower than normal, and is getting lower? Thank you for any help.

Jacob

 

[HISSIN50]

Did he blow the fusible links?

Were the new alternator and battery bench tested before installation (I've received bad ones of both right off the shelf, before even leaving the store)?

Some solid DMM readings (car off, car idling, etc) would help.

Good luck.

 

[RS200]

Could be a fuse link. Sounds like the battery, though..figures are needed.

 

[SuperStang83]

Where are the fuse links?

 

[HISSIN50]

They're off the solenoid. Check the voltage of both OEM charge wires in the rectifier plug. If you have no voltage, chances are that the links blew.

The sense circuit also has its own link.

Courtesy of S&2B's and TMoss (host and author, respectively):

 

[SuperStang83]

Thank you guys, I will check that out after he gets here and after THE GAME!

 

[SuperStang83]

We looked at all the wiring and found nothing so I think that we are going to go back and get the battery and alternator both bench tested to make sure that they are good!

 

[SuperStang83]

Both items bench tested good. Where exactly are the fuseable links? Thank you very much.

Jacob

 

[HISSIN50]

Both items bench tested good. Where exactly are the fuseable links? Thank you very much.

Jacob

They're just off the starter solenoid. Normally I have to clean all the wires and do a little digging to find the one I want.

 

[SuperStang83]

Thanks HISSIN, you always come through!

 

[SuperStang83]

I'm still having trouble chasing these wires! Where is the rectifier plug?

 

[HISSIN50]

I'm still having trouble chasing these wires! Where is the rectifier plug?

It's the alt plug that has the two blk/or wires and the white/blk wire.

I'd note that I assumed this is a stock alternator for a fox. If a 3G, 6G or other retrofit was done, this plug is no longer used per se (the same functions occur but they are packaged differently).

 

[SuperStang83]

Yeah it is still the stock alternator, and we tested that and everything was good! Chasing wires sucks!

 

[SuperStang83]

Could it be a problem with any of the wores going to the starter?

 

[SuperStang83]

The battery is only showing 12.2 volts when the car is running, shouldn't it be showing upwards of 14 volts while it is running?

 

[ninety15.0]

Yea you want to see AT LEAST 13 volts with the car running. With that being said...i am assuming that he doesnt have any underdrive pullies, or an E-fan, or E water pump. All of these things would make the car not charge well at idle.

The fuse links should be fairly easy to spot. Generally they have the proper colored wired on either side of a black section that looks like heat shrink. Take everything off of the starter solenoid and check each individual wire for burns/opens/inconsistencies.

Also make sure all the battery and engine grounds are in good shape and making good metal to metal contact! good luck man

 

[SuperStang83]

I think that it has to be a ground somewhere because there are only a few fusible links between the battery and alternator, but the battery just isn't taking a charge.

 

[HISSIN50]

Check the blk/or wires for voltage.

I dont see it being a ground issue but if you need to, for diagnostics you can use a jumper cable. Connect it between the neg battery terminal and the engine (or engine and chassis) to see if it helps. I don't think this is the issue however.

Good luck.

 

[SuperStang83]

Yeah we checked the black/orange wire from the alternator to the battery and it was continuous. He is taking his car up to Autozone in a little, supposedly there is a guy that works there that worked at Ford for 30 years, so hopefully he will be able to see the problem.

 

[SuperStang83]

Does anyone know where the grounds that would affect this are located? I would like to check them all just to make sure. Thank you.

Jacob