Battery gage needle doesn't move

[Michael G.]

I changed the engine wiring harness on one of my 63's and now the battery gage always shows a very slight discharge, but does not move no matter what the engine RPM or the electrical load situation. All else seems fine.

I'm guessing that this is a bad connection somewhere, as the gage worked with the old harness. Before I start cleaning and re-tightening all the connections, does anybody have a suggestion which connection is the most likely culprit?

Thanks,

[William C.]

Re: Battery gage needle doesn't move

Assuning you have checked to verify that the system is actually charging (Voltmeter should read about 13.5 at the battery with engine running) Moslt likely places to start are the ring terminal that grounds at the starter motor mounting bolt is mis-located aor not installed, or there is a problem at the connection between the engine compartment and the drivers compartment. That connection is at the firewall under the steering column (in the engine compartment side)

[Michael G.]

Re: Battery gage needle doesn't move

Thanks Bill, I checked the system earlier today, it is charging. The old harness had a broken tang on the bottom of the connector at the firewall, so I'm familiar with that attachment. I had trouble seating the connector and snapping the new tang, so maybe something is wrong there. I'll check both the ground and firewall connections, but look at the firewall one first.

[Richard G.]

[John L.]

Re: Battery gage needle doesn't move

Mike

[Ken A.]

Re: Battery gage needle doesn't move

I changed the engine wiring harness on one of my 63's and now the battery gage always shows a very slight discharge, but does not move no matter what the engine RPM or the electrical load situation. All else seems fine.

I'm guessing that this is a bad connection somewhere, as the gage worked with the old harness. Before I start cleaning and re-tightening all the connections, does anybody have a suggestion which connection is the most likely culprit?

Thanks,

Remove the firewall connector and check for dislodged terminals. Common problem with repop harnesses.

[Domenic T.]

Re: Battery gage needle doesn't move

I had to take apart my 67 guage and rewind it twice. One of the fine wires was burned.
The second time told me that I did not find the problem. It was a ground that was loose. As I remember I think it was the cluster ground(1971 repair).

DOM

[Michael G.]

Re: Battery gage needle doesn't move

I tested the headlights yesterday with the engine off and they don't move the needle.

I don't have the car here (where I am today), so later in the week when I get back home, I'll take off the dash connector and examine it.

Thanks guys,

[John H.]

Re: Battery gage needle doesn't move

This system is not measuring amps but milliamps. If you check the schematic you will likely find where the amp gauge wires are connected to the same wire.

Rick -

Actually, the battery gauge system measures voltage, not current; the battery gauge is a sensitive voltmeter (galvanometer). One sense wire is connected to the large battery cable stud on the starter solenoid, and the other sense wire is connected to the hot buss terminal on the horn relay (both are hot at all times). The system operates on the difference in voltage between those two sources and displays it as an indication of current flowing TO or FROM the battery. The shunt in the system is the wire from the solenoid to the horn relay buss.

[Michael G.]

Re: Battery gage needle doesn't move

I have another cluster with a working battery gauge. If I take the connectors off of the back of the original gauge and attach them to the gauge in the spare cluster, I think it should tell me whether I've got a bad connection somewhere or possibly a bad original gauge.

I not much of an electrical engineer though, so I'm wondering: could there be something else wrong that will damage the spare gauge too?

Thanks,

[William C.]

Re: Battery gage needle doesn't move

No, the approach you are thinking of will work

[Jack H.]

Re: Battery gage needle doesn't move

John is correct! The ammeter is actually a voltmeter with the face calibrated to read amps. It looks between two points in the wiring system where the inter-connect is of known/fixed resistance. Using Ohm's law (V=IR) with a fixed resistance current flow can be deduced from measuring the voltage differential.

In fact, if you want to test/verify your ammeter, a variable lab power supply dialed in the 0 to 0.75 VDC range should generate a 0 to 40A deflection of the gauge's pointer needle...