[undy]

The voltage drops as lights go on. This is especially prevalent with a marginal (typical Cobra) electrical system. Your electrical temp gauge will reflect higher temps as the voltage drops in the gauge circuitry.

Also, as the voltage drops across the board your electrical engine cooling fan will run slower (DC motor) and actual temps will raise too.

You need to measure all your voltages with the lights on and everything running. I'd hazard a guess things aren't up to snuff...