Amp meter acting like tachometer (1 Viewer)

[Drewk]

MUD looking for a little help... just rebuilt my wire harness and I dont think my amp meter is operating correctly. It is sitting in the middle when started but when I accelerate it goes all the way to the right, and when I let off the accelerator it goes back to the middle.
Thanks in advance.
Drew

 

[sggoat]

I'm assuming it did not do this before the harness rebuild?

 

[HeavyD]

Mine is doing the exact same thing, interested in the responses.

 

[B y r o n]

At an idle does it drop if you add electrical load like turning on the lights?

I could be acting normally, near the middle at idle, below if load applied and then back to charging side with higher RPM. The alternator just isn't putting out much at idle, load will drag it to the - side or discharge and RPM will increase output so + or charge indicating.

 

[Drewk]

Sggoat, you are correct it was not doing this befof the rebuilt, during the rebuilt I added a fuesable link and took apart the gauge cluster and to remove the light deflectors for better lighting.

 

[Drewk]

Byron, it does drop with a load at idle (light on ) then back to middle, but when the accelerator is presed it goes to full + 30. Let off then back to middle. Maybe it is working correctly just don't remember it acting this way before.

 

[Drewk]

Forgot to add that my fuel gauge and temp gauge are not working either. I am thinking it has to do with something in the cluster, but I have takin it out 3 times now and cleaned and looked for issues but I have not noticed any

 

[bj40green]

@Drewk do you have the 30-0-30 ammeter or the 50-0-50 ('79 and later)? Those circuits are totally different.

BTW: The FUEL and TEMP gauges are a separate circuit and have nothing to do with the Ammeter.

Rudi

 

[Drewk]

Rudi,
Thanks for the PM my rig is a 77' so it's the 30-0-30.
So it's seams like I have multiple issues going on?

 

[bj40green]

So it's seams like I have multiple issues going on?

Maybe yes, maybe no. We'll see.

How long is your battery in-active? If you have been checking circuits like headlights, brake lights, several times starting the engine but not driving, etc. you discharged your battery a fair bit. As long as the Ammeter goes up in the direction of +30 (not going strait into the corner) following the rpm's when you rev up there's not much to worry about. If you want to be sure..... put your battery overnight on a charger.
The behavior of the ammeter should be different after this recharge.

The gauges:
OIL pressure should come up directly after starting the engine with a delay of a few seconds.
Same story for the FUEL gauge. The TEMP gauges shows nothing until the engine heats up.
IF all gauges are not working check the fuse and Blue/Red wire from the fuse box to the cluster.
Check for voltage when the key is in the "on" position.

IF.... the OIL gauge is working but the TEMP and FUEL not......
Open the cluster and check the ground lip on the back of the FUEL gauge. This lip must touch the cluster housing.

The FUEL gauge has an internal VR and creates a working voltage for itself and the TEMP circuit. If this circuit doesn't work both gauges won't work.


For a lot of reading fun: Clusters, Gauges, Speedo & Odo meters

Rudi

 

[JAFO2014]

Mine is a 77 and since owning it now for about five years the AMP meter has always been erratic. I think the acid test for charging is to remove the battery cable while running and if it stays running, your alternator is charging. Mine stays running with the battery cable removed.

I've been wanting to get my amp meter to settle down. Since owning it I have purchased a new alternator and also a new regulator. Still the meter is erratic. I will see it discharge at a stop light idling, which I sort of expect. But also, driving down the road and I turn on the lights, sometimes I see it discharge or maybe the needle will be in the middle. But at a stop with the lights on, and hitting the brakes the meter goes into discharge. But always my battery turns the starter over, so I figure I am charging more often than not. One day I will focus on resolving this amp meter issue once and for all. If I do I will post my results.

 

[Drewk]

Rudi,
Thanks for all the great info in your thread! Charged the battery overnight, took the cluster back out and made sure the Fuel gauge was grounded inside the cluster, unbolted the fuse block checked all wires, checked fuses, all the fuses look good, put everything back together and fired her up and let her get to temp and all gauges seem to be working! AMP meter is still going to the + 30 with acceleration but dose not sound like a big deal, pulled the + battery cable and she still runs so alternator seems to be working also. I wish I could tell y'all exactly what I did to get it working but just not sure.

Thanks for all the help.
DK

 

[bj40green]

I'm happy that you're happy!
Let's see what the ammeter reads after driving half an hour or so. At some point the battery is full and the Amps should go down.

Rudi

 

[bj40green]

..... start engine, hook up a Voltmeter to your battery, rev her up and read the voltage.
If your Voltage Regulator is out of spec (more than 14.6V) that will explain the high amps reading.

Rudi

 

[65swb45]

As usual, you can't go wrong if Rudi chimes in on an electrical issue. IIRC, either he or Mark W. also explain how to tweak the gap on the VR to avoid overcharging, rather than just replacing the unit.