Another 300E Air conditioner Benzmac?
 

Hi everybody, I talked to Phil when ordering more parts from partshop and he reccomended I e mail Donnie. I'm sure others are having similar problems so here it goes.
First my A/C has been working intermittently for a couple years.......i've lived with it.
Now its not working at all.
I had my A/C buddy put in some freon which he did, so I know my system is full.
My compressor is running and the engine is underload with switch turned on.
Still no cold
Then a week ago the A/C mysteriously starts working........I say cool (get the pun?).
Unfortunatly its not working once again....same thing compressor is full of freon, clutch engaging, underload but no cold.
What can the problem be?
Phil said possibly the drier, could that be it?
the system has not been opened to the outside enviorment although it does have 134 in it.
It dosent seem to be taking heat off the heating side of the system (is that possible) so it appear that it might be something electrictial in nature.
Benzmac and all involved thanks in advance for the assistance
Alex

Alex,

Your car is an '89 300E?

Haasman

Yes (thanks) 89 300E no text
 

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Is it blowing hot air or NO air?
 

It could be many things but, if it is blowing hot air, it could be the monovalve. YOu are not too clear in your post...
"It dosent seem to be taking heat off the heating side of the system (is that possible) so it appear that it might be something electrictial in nature."
Need some more info!

To properly diagnose A/C problems it is necessary to answer Mr. Hidalgos question PLUS we need to know high and low side pressure and vent temperature.

On the 300E the heater valve typically fails in a normally off mode. If it is flowing when it shouldn't the problem is most likely the pushbutton control unit, but it should be checked before replacing any parts. You can simply feel of the hose before and after the heater valve. If both are hot the heater valve is flowing hot coolant to the heater core, thus offsetting the refrigerated air from the evaporator.

Get pressure readings, vent temp and give a complete description of what is happening with the blower and maybe we can help further.

Additionally on this particular car, you need to see that air is being drawn into the small grille near the rear view mirror. There is a small fan motor behind the glove box that draws air through that grill, through a tube and to the temp. sensor. If that is not drawing air, all sorts of crazy things will happen.

Good luck,

I have a similar problem but I know the blower motor is not working. When Driving you can feel the cold air from the vents.

HOW DO YOU TEST THIS EASILY? Is there any simple bypass or do you have to take apart the whole dash?

87 300E