W124 E220 Air Con Cooling...AFTER 5 mins!!

[Screwdriver]

My 1996 E220 has been facing a curious 5-6 minutes delay in cooling each time the A/C is first engaged. Here are more specifics from my troubleshooting:

1) The delay in cooling happens the first time the A/C is turned on. Once the compressor kicks in after 5-6 minutes, cooling promptly occurs each time the A/C is subsequently turned on. It's only the first time that this symptom occurs i.e. A/C pulley does not spin till the 6 minute period passes.

2) The delay does not depend on whether the engine is cold/ warm. The delay occurs regardless, the first time ac is turned on. Once functioning, it exhibits no further delays.

3) Thermostat temperature lowering does nothing.

4) Changed A/C relay near the battery as we suspected a failure. No result.

5) Once cooling does occur, it cools well. Thermostat works correctly and everything is peachy.

It's getting the thing to kick in immediately that's the problem. Any information/ guidance that I can share with my greasemonkey would be appreciated!

Cheers!

 

[sweeper]

what happens if you switch off and then back on? first thing to check, is the compressor getting 12v as soon as the a/c is switched on? if so then fault lies with compressor clutch. if not, try shorting the low pressure switch if the compressor then switches in immediatley you are probably low on gas, if not maybe fault lies in the compressor control unit. I can't really see how you get the six minute delay every time, so i would be thinking a fault in the controls somewhere.

 

[MangoMan]

There is a pressure switch which discerns if there is pressure in the system, (before operation) if there is none it won't allow the A/C to operate, causing damage to the compressor. This switch might be faulty. I think the switch is 65 in illustration in this link: http://www.detali.ru/cat/oem_mb2.as...GM=717.413&CT=F&cat=15T&SID=83&SGR=195&SGN=05
The switch will be somewhere on the A/C line on the low pressure side.
This is the only thing I can think it might be.

Ciao.

 

[Screwdriver]

Shouldnt the pressure switch trigger the fan, not the compressor?

Could this be a thermostat problem?

 

[Screwdriver]

Thank God for ol fashioned magnetic clutches.

We opened the AC clutch today and found that the pulley lining had warped and cracked off, probably because the clutch surface was uneven and didnt have enough of surface area for traction.

Machining the contact surface and replacing the pulley should solve the problem.