My compressor works but it will not kick in.

If I supply 12 volts to it, the electric clutch kicks in. There is no power on the blue wire at the low pressure switch. Where does this wire originate(it goes into a huge wiring harness.)

Is there a relay in series with this wire. If so, where is it located?

Jim
1983 300Dt

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1983 300D Turbo
1985 190E 2.3

More than likely, you have too low a charge of Freon in the system. On the reciever drier(it is a black cylinder near the condensor that has a small site glass) there is a low side pressure switch and a thermo switch (to turn on the front radiator fan). Take off the leads to the low pressure switch and short them together(the wires coming from the chassis to the switch). The clutch should engage. If it does then your refrigerant charge is too low. This switch is there to protect the compressor from running with low or no freon and oil.

I would NOT be to readily convinced to switch your system over to a 134 coolant. Unless you spend alot of $$$, you won't be happy. There alot of R12 substitutes out there. Yours and My A/C systems are getting to that age of needing hoses and compressors replaced. The flat Harrison compressor is troublesome. The hoses start to rot out and leak.

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My Truck.. 2007 DODGE, 5.9 Cummins, 6spd stick, 4X4. My car..1977 240D, OTHER WHEELS...1955 VW Oval window bug, European Delivery (Holland) with a 1700cc, 2 barrel, Porsche drum brakes. 1939 WILLYS Pick-up. 1967 Triumph 200cc Tiger Cub. 1976 Honda 550F 4cyl Motor Cycle.

Thanks for your reply. It turned out to be a bad relay on the driver side wheel well. I ordered a new one.

The car was already converted to r134 when I bought it. I have since switched to Duracool 12a. It provides a much more efficient operation. If I had my choice I would have stayed with R-12. My 5 gallon canister just ran out today while recharging my '85 190e...

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1983 300D Turbo
1985 190E 2.3