Only charging at 11.82

[monterey1962]

1988 GM ... I recently removed the dash from the car to work on the heater core plenum. Full details of what was done in the first post here.

After re-installing the dash, all three of my aftermarket gauges (oil/temp/volt) failed to work unless I wiggled wires around. I have them tapped into the yellow Accessory Power wire that runs into the factory stereo plug. After some messing around, oil and temp quit working all together.

Volt gauge only works with the wiring held a certain way, but shows a low charge of 11.82 with [Key ON] and [Key ON Engine Running]. Voltage shows 12.08 with [Key OFF]. Checked voltage at the battery and the numbers are the same for both situations.

Everything was operating properly before dis-assembly. I was wrestling the heater core plenum pretty hard, but I can't find any pinched wires. Anyone have any idea of where to start checking?

Would the voltage numbers indicate that something that runs with [Key ON] is shorting out, since [Key OFF] is at normal voltage?

Btw, all interior lights were removed, so there's no electrical drain there. Car has a 3G alt.

[sly]

might have pulled the wires a bit much and stressed the connections. How did you tap in? The taps may be pulling apart. The spade connectors may also be stressed and/or pulling the wire out of them. check the wire ends to see if they are still making good connections. You may also have a loose/resistive ground.

[1987cp]

So the system voltage is the same with the engine on or off? That sounds like a dang good sign of the alternator not charging .....

Sounds normal to me for the system voltage be slightly lower with the key on and engine off than with everything off .....

[gadget73]

Is the instrument cluster installed? They won't charge without the cluster in place to complete the idiot light circuit. Does the idiot light come on? If thats not working, the alt won't switch on either.

[monterey1962]

Is the instrument cluster installed? They won't charge without the cluster in place to complete the idiot light circuit. Does the idiot light come on? If thats not working, the alt won't switch on either.

Now there's something I didn't know.

Cluster is removed since I'm doing up a "new" one.

[87gtVIC]

You are just running off of battery power at that point.

[1990LTD]

You are just running off of battery power at that point.

+1...the light completes the circuit somehow

[91waggin]

Once you get the instrument cluster hooked up, put a voltmeter directly on the battery with the engine off and then the engine running to confirm what your dash voltmeter is seeing.

[hemihotrod402]

Is the instrument cluster installed? They won't charge without the cluster in place to complete the idiot light circuit. Does the idiot light come on? If thats not working, the alt won't switch on either.

I learned this the hard way lol

[monterey1962]

Dash is assembled and gauge cluster is in. Charging properly, now.

New problem ... When turning the headlight switch to dim the dash lights, they go from bright, to off, to flicker as I turn the knob. Going to start checking wires tomorrow.

[gadget73]

Headlight switch has a dead dimmer segment. You might get it to work with some contact cleaner on the rheostat section but if not, the switch needs replacing.

[monterey1962]

I forgot to mention ... when I hit the door lock switch with the lights off, the LED's in my doors give a slight flicker. I'm assuming I have a short somewhere.

What do you mean by "dead dimmer segment"?

[gadget73]

the part of the headlight switch that does dash illumination dimming. Looking at the switch, its the round bit closest to the knob, looks like a spring wound on a ceramic form.

[1987cp]

I learned this the hard way lol

Me too. Idiotic piece of design genius, that. Completing the circuit with a spare piece of wire is sufficient to do the trick.

[86VickyLX]

I forgot to mention ... when I hit the door lock switch with the lights off, the LED's in my doors give a slight flicker. I'm assuming I have a short somewhere.

Mine do that too. I think it's some feedback that go through the interior light circuit. I noticed that the incandecent bulbs don't flicker, I'm guessing because they have a higher resistance.