89 IROC L03 Recently replaced an alternator that was whining badly and putting out low voltage with a brand new unit (not rebuilt). Voltage at the battery w/ the engine running is ~14.5 volts. But, the cluster voltmeter indicates anywhere between 8-13 volts. Prior to the original alternator going bad it always indicated more than 13 volts. Any idea what might be going on & what I should check to solve it? Thanks!

i just had the same problem dude. it actually is still reading between 8-13 volts. I just replaced my alt yesterday. i talked to some guys on board and one suggested that the battery be recharged. I want to see what happens with this more.

That could be the problem if the volt reading at the battery matched the gauge cluster reading. In my case they don't.

I just measured the reading and this is what I'm getting:

Reading
-------------------------
Condition At Battery Gauge
--------------- ------------- --------
Ignition off 12.3 8
Ignition on 12.0 8
Eng running 14.5 13

If the battery was really at 8 volts, I would agree the battery needs charging or replacing b/c it probably wouldn't start the enging. Check yours and see if you get something similar.

I suspect some resistance between the battery and the gauge is at fault and hope it's not the cluster. I just don't know where to start looking for a bad connection or corrosion in the circuitry.

Well ... the chart didn't come out very well. Let me try again ...

Ignition off
Battery = 12.3
Gauge = 8

Ignition on
Battery = 12.0
Gauge = 8 (it may be at the low limit)

Engine running
Battery = 14.5 (where it should be while charging)
Gauge = 13 (this is low and it used to be higher before the original alternator started failing)

Shouldnt the gauge read ZERO with the ingnition OFF.Maybe thats where your problem is.Something is applying current to the gauge when off,perhaps causing the low voltage reading when ON.

Pull the guage out, it unplugs after the bezel and plastic cover is off-the guage is held in with a couple of small screws and it just pulls out. Take off the two nuts securing a small ceramic block(resistor)on the rear of the guage and if the surface where the nuts contact looks black clean the resistor with alcohol or contact cleaner. Clean the two fingers that contact the guage threads at the dash side. Don't overtighten the nuts when reinstalling the resistor to the guage,Y can crack it. Reinstall the guage and it should read normally. It's a very common problem.

Thanks Danno

Yours is exactly the kind of information I was hoping for. I'll check that out and post the results.

84 ILE

The lowest mark on my gauge is 8 or a little below that - it doesn't go down to zero. But, your right, I don't believe there's voltage to the gauge w/ the ignition off.

Danno - You're the man!

Even though the connections didn't look bad I went ahead and cleaned them up per your instructions. I aso cleaned the spring loaded contacts that the gauge plugs into and the threaded posts on the gauge itself. Now the gauge reads as it did before. Thanks for the excellent advice!

While I had it all apart I checked the voltage at the spring contacts and found the reading to be consistently 0.5 volt lower than the reading at the battery. Interesting ... but, I can live w/ that.

Again, thanks for the help. It is greatly appreciated.

Good to hear you fixed the problem. I'll have to remember this if it ever happens to me.

A half a volt is pretty normal voltage drop due to the internal harness resistance.

I did this with my 83 Z28 Volt Gauge and saw noticable improvement in the gauge reading more volts.

thanks Danno!
phil

Is it possible that the procedure that Danno has layed out would improve the alternators ability to sense and therefore improve the system charging. Or is it just improve the accuracy of the guage?

thanks,
phil