jessinak

mercedes 1989 420SEL climate control, blows cold air, only at highway speeds. up to 50mph climate control system works great. If I turn ignition off then on, I get warm air again. I have replaced monovalve, heater fuse, and coolant is full.
Hope someone can help me. Driving 320 miles at below freezing temps is getting very cold. Not to mention, the highway travelers are getting ticked off at me driving at 45mph.

jessinak

drove the car and got engine up to temp at 40mph. got on hwy, 60mph, and cold air out of all vents. after i got back, while in park, tested rpm for cool air. cool air begins at 2k rpm. unplugged monovalve, warm air all the way to over 3k.

what should i ck next?

thanks in advance,
jess

Tony Funches

I'm checking Alldata ... which is a Water-Torture Ordeal ... as is the 'Cold Air Monovalve' ...