In my '87 260e, while driving down the road the climate control will randomly turn on and off by itself. I can hear a clicking noise under the dash when it turns on and off.
It seems like maybe the pushbutton unit itself?
To make me think this even more here are some extra notes on it:
the A/C compressor does kick on but the air doesn't blow cold nor will it accept any freon. Also, by using the temperature selector wheel I can not distinguish cold from hot. Everything is the same temp.

So what's everyone's thoughts on this? Could it simply be the push button unit? Klima relay? Something worse?? If it helps, I have a 190e 2.6 parts car I can take parts off of, if need be.

Any input would be great...I'm stumped.

It is not clear what do you mean by climate control turns on and off. Does your blower motor start and stop intermittently ? Or, the blower motor is blowing all the time but the cooling turns on and off intermittently ?

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Saumil S. Patel

Sorry for the confusion, the blower itself stops and starts intermittently. This happens when the pushbutton unit is turned off.

O.K. now it is clearer. Problem: When the 0 button is pressed and the low fan switch is pressed, sometimes the blower comes on.

This sounds to me like a problem in the push button unit. But you can test this before concluding it is the push-button unit. There is a 3 pin connector on the driver side under the hood right behind the brake booster. You can remove the wire connector and test the voltages on the pins of the male connector. The first pin that is towards the engine should be ground, so you get 0V when measuring with respect to battery ground. The middle pin should have about 12V when the ignition switch is on. The last pin towards the driver side fender should have a variable voltage. Turn on the car for testing this pin. Put the climate control knob all the way for maximum cooling and select some blowing mode, e.g. from the top grille (not economy or 0). When you press the high speed switch on the push button unit, you should get about 7.5V. When you press the low speed switch you should get about 5V and when you press the 0 button, you should get about 1V or lower.

So when you get into a situation where the 0 button is pressed and the blower motor comes on, if the push button unit was bad, you should see some voltage on the third pin which is substantially higher than 1V. If the push button voltage is o.k. (< 1V), and the blower motor is running, then the problem is in the blower motor regulator.

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Saumil S. Patel