Re: Twitching gauges (was: 82 4000s no start condition - results)

[Eddi Jew <jew@rysa.dtc.hp.com>]

 >>> My next question as I'm about to add a oil pressure gauge, is how 
 >>> can I get my gauges to stop twitching when my stereo hits a bass 
 >>> note?  Turning the volume up has the effects of raising my oil temp. 
 >>> about ten degrees.

 >> Don't know about '82 4000's, but on the 84-88 5000 series there is a
 >> voltage regulator in the dash whose output is used as a reference
 >> voltage for all the gauges. 

Took a quick look at the wiring diagram. The voltage reference regulator
is getting its power from the same tap as the clock's power (my manual is 
also for 84-88 5000).
 
 >> This voltage regulator's output may be getting affected by the stereo. 
 >> How powerful is your stereo? If the current draw
 >> is considerable, then it may be causing a significant voltage drop 

 > Maybe. This depends on where the radio's power is tied at. If it's a 
 > powerful aftermarket stereo (or if you have a separate amp), and it's power 
 > is supplied by the same branch as the dash's (don't have the wiring diagram
 > here), and using the standard radio wiring harness, then the voltage drop 
 > might be limited to just that branch/circuit.

The radio power source does seem to feed over to the clock or its light
dimmer, and also the A/C programmer, but I'm not used to reading this kind
of schematic- some of the "wires" just seem to be unconnected, yet there's 
hint that it's connected to the fuse.

Sorry for being so vague about this. I think the clock or the light dimming 
circuit might be the common +12V point for the reference and the radio. The
main power for the instrument cluster is a different fuse than the radio's.
I would try measuring voltages downstream of the radio's fuse, to the point
where it branches out to the clock. Maybe you'll find some weak links.

-- Eddi