Hello everyone with more knowledge than I,

I am seeking guidance to help me solve the following problem:

1) When on, air conditioner significantly lowers idling speed to the point where cars starts to shake - when switched off car idles smooth. When accelerating up any type of hill from stationary, very slow and gutless when a/c is on.

2) Stationary or at low speeds, A/C does not get very cold and can just switch off (compressor switches off) I then need to switch off car/ignition and restart to get compressor back on.

3) On the highway, travelling at speed with good revs A/c operates very effectively.

Would dearly appreciate any advice to point me in the right direction.

Thanks.

Jason

What engine do you have ?
Does it have a ' Rack Dampner' adjustment available ?
Have you adjusted your valves and checked the timing of your IP ?

__________________
1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/diesel-discussion/10414-help-i-need-check-stretch.html

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html

There are no valve adjustments on an 86. It sounds like your compressor is dragging for some reason. The car can detect when the belt slips on the compressor, which is why it shuts off at low speeds sometimes.

Is your car still using R12? Does the electric radiator fan work properly? When traveling on the highway does using the air con still cause a huge power loss?

-Jason

__________________
1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

The car could be either a 300SDL (W126) or a 300D Turbo or N/A (W124) -- I don't know what Mercedes exported to OZ in those years. Either way it should have an OM603 with electronic idle speed control. If so, then there's a problem with the EGR electronics 'cause that's where the idle speed is controlled from.

The first to check is the over-voltage protection relay (OVP) and its 10 Amp fuse. Next is the IP and its various electrical connections. The EGR box itself is last, only because it's historically very reliable, there's nothing you can do with it, and it's very expensive.

Jeremy

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

If the OVP wasn't working the AC wouldn't come on at all... the KLIMA relay needs the engine speed signal to turn on the compressor.

Adjust idle speed control knob (lift up to turn) to test system. AC overcharged?

Thank you for the feedback.

Engine is a 603 - chassis 124 - non turbo - I think one of the first 300D 124s.

Car has been converted to use R - 134A.

A/C not overcharged and idling is fine when A/c is not on.

Electric radiator fan tends to only come on when it gets pretty hot (that is normal says my auto electrian).

When travelling on the highway can't detect too much loss of power, I assume due to higher revs..


Could it be the Klima relay???

Thanks for your thoughts...much appreciated.

Jason

To me it sounds like the compressor is getting overloaded at idle and using too much power. How is your radiator fan clutch doing? When you shut the car off does the fan keep spinning for a while?

-Jason

__________________
1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

Do you know what type/make AC compressor you have ?

__________________
1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/showthread.php?threadid=10414

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html

My radiator fan clutch is busted - a bolt is attached, therefore the fan runs all the time when engine going and stops when engine stops.

Could this be affecting the compressor?

I am unsure of the compressor type or make but I will find out.

Thanks for your help thus far....

Regards,

Jason