The usual suspect again, my AC/Heather Fan blower is working ON and OFF, 3 months ago, I had the AC/Heather Fan regulator changed due to the fact it was only blowing air on minimum setting only, once the module was changed, it worked fine, however, the unit has been acting up for the past 9 days, the only thing I’ve discovered, there is a pattern when the unit will work and when it will not, every morning I will start the car, and the unit will work for an hour or two, then by the afternoon, it will stop working, this has been happening for the past 9 days and the working and non working pattern is consistent, I’m running out of idea on what could cause this. I hope the AC regulator has not gone bad again, any suggestion is welcome.

Thanks, Neil

 

Sounds like perhaps the fan motor is getting hot and there is a failsafe heat switch that cuts it off if it gets too hot?

 

Alan you may be right, a new motor was installed yesterday and it is doing the same thing, what I discovered is, any time the engine temperature reachers 80 degrees celcius, the fan stop working, the mechanics are running out of ideas now. Any insight?

 

Did you change the thermostat sensor? It is located near or on the housing for the thermostat. Also, the the fan switch itself could be bad. Question, is 80 degrees C as hot as the engine gets? Normal operating temp for these engines are between 80 degrees and 95 degrees C? How about the anti freeze, is it Mercedes, or an approved long life brand. Prestone don't work in these cars. Other then that I where you mechanic is at????

Allan

PS: My fan on my 99 C290 seldom comes on. Only in hot weather it will, I use to worry about it not coming on at all, but the techs at Mercedes told me these engines "love to run hot" and as long as your not in the red, your OK.

 

We haven't touch the fan switch, only the motor and the AC regulator fan that is attached to the motor was changed. I'm not sure if the Climate unit is deffective, but it seems to be working fine. To answer your question, the engine tempareture stays between 80 and 90 degrees celcius. I'm not sure if the antifreeze in the car is MB 'cause I only had it for a few months and has yet to change it, but I will look into it, it will not hurt to change it.
My mechanic is in New Jersey, it is a used car dealer, but they only sales MB and BMW, one will think they know how to work on this car, I will mention your comments to them.

 

The easiest way to tell if the antifreeze is MB is the color, it is brown. MB, as well as BMW, AUDI has permanent antifreeze not a days. My wife's 94 Audi has permanent antifreeze, never changed it in 10 years, just top if off once in a while. Now I understand, there is no water added to the newer formula of these anti freeze. Yea, my mechanic worked for MB and BMW also, as a tech, and sometimes these guys miss the obvious. have them check the switch. 80 to 90 C is normal operating temp by the way, year round. In my owners manual it says you only have to worry if it goes into the red and stays there. As I said newer cars are designed to run hot, to burn off pollutants. If the fan switch is OK, I wouldn't be concerned unless you go into the red and it stay there.

 

Alan, the antifreeze is not MB, I will drain it this weekend, we found the issue with the fan, it was a wiring problem between the fan and the climate control unit, the car was sent to an electronic shop and they fixed it, my SRS light use to stay on for a minute or two after you start the car, but it looks like, by fixing the fan, it also fixed the SRS light that was on for more than a minute (it could have been low voltage)
Thanks, for your insight.

Neil