So the wiring issue in the fuse box was related only to the headlights (combo switch on column is broken).

Fuses have been replaced. Nothing changed with that. Sometimes it seems like the AC compressor engages; RPM drops a couple hundred then goes back up.

Switching from EC to 'white down arrow' button will increase fan speed, even with the fan already set to full speed.

More air is coming from the center vents than the driver/passenger vents; even less coming from the passenger vent.

This seems like it is either a bad relay or a short in a wire. If it was a relay, is there a way to override it? If so, how?

Thanks.

Bill

Looks like you haven't gotten an answer to your earlier question about the blue relay and its fuse. That blue relay (with a 15A spade fuse on top) and the companion green relay (with a 30A fuse on top) are both for aux fan, not for A/C compressor. The blue relay is for stage 1 fan speed, the green for stage 2 fan speed. As has been mentioned, the relay for A/C compressor is not in the main relay box on the driver side firewall, but on the right side of the firewall behind battery.

__________________
1988 California version 260E (W124)
Anthracite Grey/Palomino
Owned since new and still going strong and smooth
MBCA member

Past Mercedes-Benz:
1986 190E Baby Benz
1967 230 Inherited from mom when she downsized
1959 220S Introduced me to the joys of keepin' 'em goin'

There are only 10 kinds of people in the world--those who understand binary and those who don't

Just to be clear, you are saying the firewall is in the trunk? Because that is where my battery is. Sorry, couldn't resist.

So the relay should be on the firewall behind where the battery would normally sit? Is it just one relay or is there something that you can tell me specifically to look for?

Thanks again.

LOL. Oops, you got me there. Sometimes when I'm typing on auto-pilot I forget that not everyone has a W124. Right, I'm talking about the electronics compartment, where your OVP and fuel pump relay are also located. May be more in the middle of the firewall than the right. One relay, p/n 002-545-18-05. The older ones have the word " Klima" printed on it.

__________________
1988 California version 260E (W124)
Anthracite Grey/Palomino
Owned since new and still going strong and smooth
MBCA member

Past Mercedes-Benz:
1986 190E Baby Benz
1967 230 Inherited from mom when she downsized
1959 220S Introduced me to the joys of keepin' 'em goin'

There are only 10 kinds of people in the world--those who understand binary and those who don't

This car does not have a Klima relay, or any relays handling the AC compressor.
The Base Module is the one that sends the 12 volts to the compressor clutch.
I do not know which wire.
Your best bet is to apply 12 volts directly to the clutch and see if it engages. Should not draw more than 4 amps. Another method is to check the resistance of the clutch coil. It should be 2.5 to 4 ohms.

__________________
1999 Porsche 996 Carrera Convertible
1994 420E - SOLD
1986 300E - SOLD, what a car
609 Certified