Generator gauges increase when headlights are on

[The Newell]

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 Newell to build a better 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. I did not change any wiring in the console or move any 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.