Before I start tearing into the dash, etc. I have a question perhaps someone has an idea of what to look for. I recently removed the diesel generator on my 1993 Regency to build a sound enclosure. It performs well and all power is fine. But last night while preparing for a trip I ran the generator (with shore power plugged in) and noticed the oil pressure gauge and temp gauge jump up about 1/2 inch when the headlight switch is turned on. The oil pressure reads 60 (versus 45) and the temp gauge will rise to 195 from 180. I did not change any wiring in the console or move any grounds. I did work my way around the grounds and lights in the main dash following suggestions I read here to solder, shrink wrap and tie wires carefully to insure solid grounds. All the dash gauges remain at their normal readings and I don't have any fluctuations of power frequency or voltage in any appliances. The coach runs fine with the exception of the cruise control which will turn on and off but wants to accelerate rather than hold speed. That condition existed when I bought the coach and I just figured I didn't need it anyway and since parts are not available I just leave it off. I know that many problems arise because of faulty grounds but I have not seen only two gauges rise like that while all the others remain in normal range. Any ideas would be appreciated.

CORRECTION: I just ran the generator without any shore power and the condition is the same, but I must correct one statement. The Oil Pressure Gauge DROPS from 45 to 25 while the Temp goes up about 15 degrees. The actual temp of the engine and oil pressure are correct when the lights are off. (Measured with a plug in pressure gauge and pyrometer on radiator)

Are the headlight dim switch and cruise control actuator on the steering column in the same stalk? Do you have a Spartan chassis where the lights and cruise are in the steering wheel hub electronics?

This is usually one of two things. Bad ground wire is one, but usually not heavy enough 12 volt line. When you turn on the headlight the voltage drops to the gages changing their reading.

It has been my experience that the voltage has to get REALLY low to effect the gauges, there are internal voltage regulators in the gauges so that battery voltage swings will not produce much variations. What does your dash mounted voltmeter do?

HOWEVER--

Bad ground connections can and will cause gauges to go wild, the type of changes you describe are wild.

When my alternator went bad, the battery voltage went as low as 10 volts and I had a very slight meter reading change, temp changed only a few degrees, oil nothing and the fuel gauge slightly.

I have dash mounted headlight/dimmer - Gillig chassis. Since the engine was not running I have no indication on the dash voltmeter, but that may be the problem - I will try with the engine and the generator running and see what happens - Many thanks to all.

The results are the same - oil pressure gauge drops and temp gauge rises with engine running, good alternator and all systems working.