My '91 240 has an air conditioner/overheating problem. The gauge jumps up real fast in a random way, not always when I'm in stop and go traffic (although usually) and sometimes when I'm zipping along. I had a new thermostat put in and from what I read in these pages a waterpump is not the way to go (although my mechanic thinks it is.) What's my next step? Clean out the radiator? What's this I read about the temperature compensation board? Is looking at that a last step? My car does have other electrical problems. Thanks for any ideas!