battery won't hold a charge

Just installed a new battery and alternator in a 1972 Bronco. The voltage gauge shows a discharge whe the truck is running. The mechanic thinks the gauge was installed wrong. A wiring diagram or some advice would be appreciated.

A quick check is to use a meter and check the voltge at the battery terminals. It shold be atleast 13.5 with the truck running. If not either the alternator is bad or the voltage regulator is bad. Since you said the alternator is new, I would get a new regulator and install it, that is the approx. 3 x 2 inch silver can usually mounted on the wheel well.

The attached diagram is from a 83 EVTM but the charging circuit should still be the same. If after changing the voltage regulator you are still not putting out around 13.5v then you may just have gotten a bum alternator.

The voltage regulator is that shiney thing just under and to the left of the solinoid.

Let us know how you made out.

Good luck,

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Just installed a new battery and alternator in a 1972 Bronco.  The voltage gauge shows a discharge whe the truck is running.  The mechanic thinks the gauge was installed wrong.  A wiring diagram or some advice would be appreciated.

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Hey I appreciate the quick response. I'll be on the phone shortly with the mechanic. Check back and I'll give you an update.

Hey I appreciate the quick response.  I'll be on the phone shortly with the mechanic.  Check back and I'll give you an update.

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http://www.bronco.com/technical/wiring.php Look here

Still the same old stuff with a new voltage regulator. They say the alternator is good. We're bringing the wiring diagrams to them today, hopefully that will help.

Sorry I can't be there to help. Did you do the voltage check prior to changing the voltage regulator? If so, what was the reading? How about after changing the VR? If you are not getting about 13.5 V, the alternator is not putting out. If that is OK, then your mechanic is probably right. The gauge reads minus when the circuits are drawing from the battery and plus when the battery is drawing from the alternator, (taking a charge). When the battery is fully charged the meter will be in the center and the circuits will be drawing what they need from the alternator.

The diagram I gave you before doesn't show a meter circuit, it is only for a warning light setup. Attached is a typical meter setup. The wire labled as a shunt is a black with orange wire running from the alternator to the solinoid with a couple of other fancy connections to make the meter work.

Good luck,

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Thanks again, I sent this diagram to the mechanic, hopefully this will help. They did check the voltage before the regulator was changed, it was about 12 volts then. After the regulator was swapped it was still the same. Sounds like the alternator to me, but what do I know! The mechanic is saying something about 3 wires, one being that black and orange wire, and two other wires that go into some sort of pack, but only 2 wires come out. Does that mean anything to you? Also he did say that the black and orange wire was burnt up when we brought the truck in, could that a problem even if it was replaced?

Thanks again, I sent this diagram to the mechanic, hopefully this will help.  They did check the voltage before the regulator was changed, it was about 12 volts then.  After the regulator was swapped it was still the same.  Sounds like the alternator to me, but what do I know!  The mechanic is saying something about 3 wires, one being that black and orange wire, and two other wires that go into some sort of pack, but only 2 wires come out.  Does that mean anything to you?  Also he did say that the black and orange wire was burnt up when we brought the truck in, could that a problem even if it was replaced?

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New regulator "MUST !!!!" be bolted down to the fenderwell before {grounded}plugging the wires in or it will be toast

thank you i'll make sure of that