jhutchison

My climate control system is very unpredictable. The ac works intermittently. Sometimes I get conditioned air, and sometimes (most of the time) I don't. When I switch to defrost (the left-most switch on the climate controls), it blasts ungodly hot air, regardless of the temperature setting. Any thoughts as to what may be wrong? Thanks for your time!

lsboogy

I had mine go out, they are a pretty simple change out. Germanstar and autohauzaz have them for a couple hundred bucks. I had very similar symptoms before I changed mine out. It might be your temp sensor too.

akuma4me

Just replace the "AC Relay", u can pick one up at the wrecking yard for less than $30.00. At the dealer, its about $220.00

ds190

That's how the defrost setting is supposed to work- full heat, full fan, AC compressor engaged.

Take a 1cm x1 cm piece of paper and place it over the vent up in the overhead light switch. If it sticks there, you have ruled out a bad aspirator or sampler motor, which pulls air through that vent across the interior temp sensor. If the paper falls off, then that little motor under the right dash vent in the dash is not sucking air, and the temp sensor gives a signal for full heat, then full cold, etc.

Is the charge of r134 refrigerant correct? If not, the compressor won't run. When you do not have cold air, did you look at the compressor to check if the clutch is even engaged? That "AC relay" he refers to is called the Klima relay, which controls the compressor engaging on. Not all 124 cars have it- that function was wrapped into the MAS control unit for a few years.

There are other things to check before buying a reconditioned Climate Control Unit (the pushbutton unit), about $250.

jhutchison

OK. I have also noticed that whenever my AC does not work, my Cruise Control does not work either. When the AC DOES work, the cruise control works. Thoughts???

lsboogy

Might be the case - E Class owner's bible (good book to own) has a possible soln page 323

Pull the instrument cluster, and there is a six pin connector behind it, just to the right of center. Contacts are bad in the connector - you can either just try to clean them out, or replace the connector (the dealer can get you a brand new one if you want). Same symptoms as you describe - CC not functioning correctly, and A/C blower speed is not working

You might also look at the harness under the fuse box.

Floobydust

You should also check the condition of the lower wring harness that connects to the compressor. I believe that both the A/C compressor and pressure control wiring and the cruise control wiring run in the same harness at certain points. Also check to make sure the your serpentine belt is tight and in good condition. The A/C controller detects slippage and will shut down the compressor if it occurs.

Clukenbill

If you hear a sound like a clock ticking when you move the temperature switch from hot to cold ( not all the way to recirculate air) then i know exactly what the problem is. There is an electric motor that opens and closes the heater valve. This regulates how much hot coolant circulates through the heater core. The motor is too weak to completely close the valve. The clicking or ticking noise is the motor attempting to close the valve. The part is about $100. The dealer wants over $1000 to install. It involves taking the dash out completely. Sevdral days to complete.

Clukenbill

If you wish to view this motor you can take the dash glove compartment out and on the left side behind the metal reinforment tube you can see the mechanism. You can't really see the motor but you can see the linkage and the top of the valve. To verify you can move the temperature contol swich from hot to cold. If the linkage stops moving and then you can move it by hand more it is the motor.

wbland

Isboogy, (or anyone else) can you recommend a source where I can buy an X53/5 six pin connector? The blower on my 93 300ce has shut down and the tech I brought it to advises that this part is the problem but has been discontinued by MB. I am having trouble finding any one that knows what it is, much less finding one. Any assistance will be most appreciated. Will

Clukenbill

If obsolete then use any connector. Of course one woulx have to change both.

wbland

Thanks. Can you explain what you mean when you say replace "both"? Will

lsboogy

It just routes the hall effect sensor to any number of places on your car. The green wire on the front goes to the hall effect (speed) sensor connector on the speedometer housing, and the rest of the wires go to other things (your pushbutton control for one). You should be able to just get any 1:6 breakout block at an electronics supply store (or just go to digikey dot com) with a 2A current rating and use that. If you are in a pinch, just twist all the wires together and wrap with electrical tape.

Clukenbill

By both i mean both the male and the female connectors. Make sure the wires don't get mixed up.

wbland

Thanks guys, I'll give it a try. Will

Dave2001

Hi. I have a 2001 CLK E320 benz. The issue I'm having is this.
1. When I first start the car. The climate control will work fine. After about 1 or 2 vminutes the screen would go blank. Nothing works. Then the fan under the hood would come on and stay on.

If I let the car sit and repeat the process. It would work again for another 1 to 2 minutes.

The AC works fine as well as the heat until it loses power.
Any help would be appreciated. Thank you.