Hello all,

I have to go down to Arizona, but my car is acting strange...

1) All temp readings are from the climate control. These are actual sensor readings. With A/C on, the heater core temp goes down to normal operating temps of high 30s. A/C is cold, but evap sensor reads 60-65F. Can't possibly be! Bad sensor?

2) When I'm stopped, even for a traffic light, on a warm-hot day, the ambient temp starts climbing every second as high as 140F and over limit of the sensor. HOWEVER, the in dash display shows stable outside temperature. What's going on?! If the sensor is bad, why in-dash shows the right temp??? When I start moving again, the temp goes down on the sensor readout at a slower rate. Again, in dash display shows no change. Any ideas? Do I need a new sensor, and where is it located on my 1998 C280? I can't find it. I have no front license plate mount to look behind.

3) Please, someone help me with all three. The third thing I just noticed, while looking for the evap sensor. I read that fan clutch should be engaged when the engine is at oper. temp. I idled the car with A/C on until coolant reached the usual temp, and then stopped the engine. The fan continued spinning. Is the clutch out, or did it not get hot enough? I did notice a higher coolant temps the other day when it wasn't even hot, 85F I think it was, and I was pushing 90-95C coolant temps with A/C on.

This is the only car I can take down to Arizona, please help with my three problems...

1) most likely low on refrigerant OR the evap sensor is bad.

2) Normal, the cluster display only changes while the car is in motion.

3) Sounds like normal operation as well. Even 100C is not hot!

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

Quick reply... My understanding that heater core and the evap run at about the same temp when you had your A/C on for a while. Air is cold, no way it's in 60s F. Should I simply replace the evap sensor?

Ambient temp sensor... where is it located on my 1998 C280? In case I would have to mess with it later on.

Thanks a bunch again!

Heater core temp is going to be slightly higher. Replacement would be up to YOU.
In the bumper on the drivers side.

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

Anything else you recommend I check or change before the trip? They say it gets really hot down threre. I'd hate to be stuck with overheated car on with no A/C. Mother-in-law traveling with us.