I have seen similar things about the 190.

Mine is a 1985 500 SEL, Sometimes, blows cold air out of all 6 vents.
Other times, blows cold out the two center vents, and two lower right and left vents. But the left and right upper vents sometimes blows hot air, and through the defroster.

Recently, had the air conditioner go whacky. The compressor (has two terminals) and aux fan was not working. Mechanic said that there was no ground, and to ground either terminal to the frame from the compressor. Air started working fine. But itermittently, this problem above started. Also get frost on the outside of the windshield from cold air off the defroster.

The tubes at the base of the console, had cool air, but once I connected the console back up, no air at all flowing through the rear vent.

Today, I switched from air, to defrost (to try to clear the windshield (minor frost)), and switched back to air. When I did so, smoke or something came out the center right vent for a millisecond.

Why both temperatures at the same time out of different vents?

And id someone knows the answer to the other problems here, feel free to advise.

My question was, why did the air work fine all this timel wouldn't one of the two terminal plugs on the compressor be a ground anyway? Which leads me to think that one of the wires had a split in it?

Baffled by all this.

Early 126 cars(yours) had a fresh air blend door problem.

On the now defunct Ritter-Easley list, there was a how-to on reducing the about of ambient air drawn into the system.

You might try using the SEARCH faculity and see if anyone copied that info into a post here.

I would look into this first.

__________________
Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"

Also check your mono valve for proper operation. When the seal starts to fail, hot water will enter the heater core erratically and send heat out when it shouldn't. This is a common problem! The mono valve can be rebuilt...I think the rebuilt kit is $49 and available through all MB vendors (including this site).

On this early 1985 500 SEL, can you tell me where the mono valve is located? Does it look like one of these?

Attached Thumbnails

       

Starting from the left, look at photo #3. The right side of it shows what I'll call a silver colored plate. This whole unit is what some would call a heater control valve. The monovalve replacement part is photo #1.

The silver plate is fastened with 4 phillips screws(small heads). The plate comes off and the piece in photo #1 comes out afterwards.

This heater control valve is on the passenger side back by the firewall. At least that's where it is on my model.

__________________
Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"

Hey Mike, thanks! Got the rebuild kit today. Water pump leaks slightly too, so I got a new water pump to put on also. Any words of advise for the water pump and thermostat replacement?

I heard the blue gasket sealer is the least favorable.

I have no experience with the V-8 water pumps. Here's a pointer to online MB repair info. This may help.

http://mb.braingears.com

__________________
Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"

Yes,

I have that already and have printed the section on water pump replacement out.

Thanks