[challyrtse]

I have a 1990 Plymouth voyager, 3.3l V6 with around 165,000 miles on it.
Sometimes, for about the last week or so, when I turn my headlights on, the check gauges light illuminates, the oil pressure and engine temperature gauges slowly peg upscale, and the high beam light and both blinker lights glow dimly. If I vary the brightness of the instrument cluster lights (by adjusting the dimmer switch), the gauges change with it - the brighter the dim switch is set the higher the gauges read, and the lower I adjust the dimmer, the lower the gauges read. Interestingly, this only happens sometimes; other times when I turn the headlights on everything works perfectly fine. If I adjust the dimmer switch to turn the dash lights off, the gauges work just fine - I just have to turn the inside lights on to read them!
So, I replaced the headlight / dimmer switch because I figured that was common to all of the malfunctions that I noticed. Sadly, the problem still persists.
Has anyone ever heard of this happening before? Any ideas as to what the culprit could be? My next step woul be to replace the temperature sending unit and oil pressure switch, but that still doesn't explain why the blinker lights and high beam indicator would illuminate...
Thanks in advance for any help!

 

[ImperialCrown]

Welcome to Allpar. I would suspect an electrical grounding or feedback issue. This could be from a bad (high-resistance) connection at or on the cluster circuit board.
The illumination lamp current may be finding a normal ground path with high-resistance and then trying a lower-resistance ground path through the ground-side of the gauges. Electricity will always choose the shortest path. These can be intermittent.
Start with cleaning the contacts, gently re-springing terminals for better contact with pins, examining solder joints for fractures and making sure that the instrument cluster-to-body grounds are secure.
Locating an intermittent contact can be difficult if it doesn't act up and by wiggling connectors you may actually scrub the oxidation off a terminal contact point and make a formerly bad connection now a good connection and 'fix' the problem.
I would expect to see some brass or copper contact 'tarnish' on a 22 year old vehicle.

 

[challyrtse]

Thanks for the reply! That makes sense. I'm going to try to locate the ground leads and clean those contacts all up. Hopefully that's it, I love cheap fixes!