W140 A/C Problems - PeachParts Mercedes-Benz Forum

keitharm · #1 09-10-2002, 09:30 PM

I've had a string of problems with the A/C in my 1993 400SEL. It's like the blower motor is smoking crack. It won't come on at all, then suddenly it's blowing full blast. Then for no apparent reason, it'll quit all together.

After reading some of the posts, I figured it was either a faulty temp sensor or a bad control unit. I changed the control unit, and have the sensor on order.

Then today, the blower won't quit even when I turn off the engine and pull out the key. What's that all about? I ended up disconnecting the plug at the blower to make it quit so the battery wouldn't drain.

joe p · #2 09-11-2002, 08:36 AM

blower regulator.

Joe

mbdoc · #3 09-11-2002, 08:38 AM

Does the "rest" light(A/C pushbutton) stay on when the key is removed? IF so then the problem is in the control unit itself. IF not then the problem is the "blower regulator".

keitharm · #4 09-11-2002, 10:12 AM

Thanks guys. The REST button does not stay lit, so I'll be replacing the regulator. Anyone know where it is? Anyone know where I can get a shop manual for the W140? Everyone I've spoken to says it's never been published.

stevebfl · #5 09-11-2002, 10:21 AM

The regulator is on top of the blower which is easily accessed under the black plastic cover at the base of the windshield passenger side (engine compartment).

keitharm · #6 09-11-2002, 10:27 AM

Thanks to all. This is an unbelievably helpful forum. I'm reasonably competant mechanically, but I'm new to the MB world and without a shop manual I tend to struggle a bit.

Thanks again. I'll be replacing the regulator tonight.

joe p · #7 09-11-2002, 12:58 PM

LOL, I've been wrenching for 20+ years and struggle without shop manuals on a lot of things. :-)

Joe

JimF · #8 09-11-2002, 08:45 PM

Similar problem happened to me. Check it out: complete w/ pics!
A/C blower's output is low . . .