hello again to all, i just wanted to see if anyone has any knowledge as to why my 99 E300 check engine light comes on when the car idles for not even 5 minutes with the a/c operating on a hot day 80f +? it stays on for about 10 startups and shutoffs then clears. clutch fan seems ok. aux fans run on low speedwhen a/c is switched on.do they have a high speed? when movingon the road temp gaugeusually reads 80C. sometimes it will reach 90C and it seems like thats when it acts up-. thanks.

 

I have experienced some vehicles that heat up at an idle with the a/c on, but I think I recall it was longer than just 5 min. to be significant. [/align] If your gage is giving a faulty reading and actual temp. is higher, that could account for it. Suggest remove radiator cap with engine cold, use an accurate thermometer to test water temp., start motor.... A/C on and make comparison. I actually prefer to use a thermocouple on the radiator hose with something wrapped around for some insulation. You could try it with a thermometer too. Just be sure to have a good contact with the tip and the hose. If the gage reads significantly low you could have an overheating problem and a faulty gage. If they agree, the sending unit seems ok too, and then the overheat/check engine might be getting triggered by another sending unit. Could be it's own or a fan sending unit. You could check them in a pan on the stove with a multimeter or some such arrangement(lightbulb/battery) using thermometer to check when switch closes.[/align] Just some rambling thoughts. good luck[/align] [/align]