I do not know if MB uses a separate fuse for the compressor or not. If the clutch engaged when you jumped it from the battery, then you know the clutch is good. Bridging the pressure switch wires should have resulted in the same action, providing that the A/C system was turned on.

IIRC, on the compressor, the brown wire is to ground, and the green wire provides the 12 v. I could be wrong, and it may be the opposite. A volt meter with a continuity circuit will tell you.

So, check the fuses, and check the wiring for voltage and continuity, and good, clean connection.

You may have a bad pressure switch as well. If you have good pressure, you should get a good continuity reading. I do not know if this switch completes the circuit by closing to ground or to voltage. I do know it must be closed. This switch should be mechanical IIRC, so continuity can be tested with the system and the engine turned off, unless it requires voltage to sense pressure.

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RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K

90 Dodge D250 5.9 Cummins/5 speed. 400K

I recently had this same exact problem on my 300ce.... it turns out i didn't have the compressor wires hooked up correctly.... i had to cut the connector from my old compressor and splice the wires... well... the splice didn't hold... a mechanic used electrical splices to hold it... he bailed me out...

i was frustrated like you.... however, then it turns out my brand new compressor has a hairline leak in the casing... the company is sending me another.... for now... i used some metal epoxy to seal the hairline crack..

i have to put some more dye in there to see if its holding... right now the pressures seem to be ok...and it's cooling , so i may wait a bit..

i am in no hurry to get the defective compressor back to the company i bought it off of... i am not even sure if i will send it back...

if i take it off.. then i have to vaccuum and recharge again... sorry to vent

hope the shrimp and crawfish are tasting good this season...

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1989 300ce 129k
( facelifted front,updated tail lights, lowered suspension,bilstein sports, lorinser front spoiler, MOMO steering wheel, remus exhaust,stainless steel brake lines). (Gone)

1997 s320 154k (what a ride). Sold with 179k miles. Replaced with Hyundai Equus

1994 e320 Cabriolet 108k



1972 280se 4.5 153k Owned for 12 yrs, sorry I sold it


[/SIGPIC]

I did not jump the low pressure switch i bridged the connections on the switch. i misunderstood some directions. I'll try that. It was freeze 12 i used. It was said somewhere that it runs coller and on a lower compression than 134. I don't think i could get R12 if i wanted it. I'm not licensed to buy it, if i knew where to get it.
I'll order some more from diesel giant. That is where i got all the parts, refrigerant, and can tapper.
Something I thought was odd when filling the lines. I attached the side cantapper to a 134 open /close valve used to tap into the top of a 134 can. i then used the 134 hoes to connect to the low line to fill. I've always found that when i used to fill my other diesels when lo that the can would become cold and seemed to empty in a short period of time. The cans did not get cold. I lost freon connection and disconnecting, I don't dought that only half of each can actually went into the system. then part of my problem could be that I later acecked the perssure with a old walmart gague i attached to the single hose i used to fill the system. On the can tap port that has the 134 threads there is a fill / release pin in it like in the fill connection on the low side system hose. When i screwed the walve in to depress it i seemed to bend it. the valve is designed to tap a 134 can not to depress the release .

As you see i can be quite wordy. A Cajun trait. I think I'll remove the pin when i get more freon an just controll the release with the open / close valve. Thanks. Ihave 4 of these diesels and have been driving diesels for 35 yrs now. I'm just starting to tackle them my self to a greater degree. Probably be cause I didn't have 4 before the kids grew up. Well off to LOWES and a different kind of fix it (WORK).

NO LUCK AT ALL LIKE I ORIGINALLY SAID. WIFE JUST TOLD NE THERE IS A LEAK ON HER 300CD 84 AT THE WATERPUMP SEAL. i THINK I GOT THAT BUT I'LL INQUIRE IF I NEED. I DON'T KNOW HOW I MANAGED BEFORE THE FORUM. I PAID$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$ TO SOMEONE ELSE. LATER

I didn't see what chassis or motor this is for. I know on my W126 420SEL there are a few sensors around on that engine that could prohibit the compressor from coming on. RPM sensor, coolant temp sensor, refrigerant pressure sensor, and I think that the motor has to run 600rpms for 10 seconds before the compressor will come on. Blah blah. Makes me love the manual system in my 240D soooooo much.

Believe me brotha.....we all know your pain.

Remove the two leads from the low pressure cut-out switch. (Not the temp switch.) With the ignition switch in the 'run' position and the a/c selected 'on', connect the two cut-out switch wires together. If the compressor does not engage, you have a problem somewhere besides the cut-out switch. To exclude the cut-out switch as a problem, check for continuity arcoss the terminals with the wires removed. Continuity would indicate the switch is closed and not part of your problem.

1980 300d r4 compressor

ANY THOUGHTS ON THIS PREIOUS POST I MADE IF I WASN'T VAGUE. (**) Something I thought was odd when filling the lines. I attached the side cantapper to a 134 open /close valve used to tap into the top of a 134 can. i then used the 134 hoes to connect to the low line to fill.***** I've always found that when i used to fill my other diesels when lo that the can would become cold and seemed to empty in a short period of time. This time the cans did not get cold. ***I lost freon connection and disconnecting thinking the can was empty cause it was still room temp*******, I don't dought that only half of each can actually went into the system. then part of my problem could be that I later checked the pressure with a old walmart gague i attached to the single hose i used to fill the system. On the can tap port that has the 134 threads there is a fill / release pin in it like in the fill connection on the low side system hose. When i screwed the walve in to depress it i seemed to bend it. the valve is designed to tap a 134 can not to depress the release .

I just checked my midas bill where i took it to get a vacuum done and the bill states they (tested a/c system for proper operation, test for leaks.) If he pressurized the system when empty could that have prevented the freon I tried to put in from going in the system. After only about 20 min he came in and said he didn't find any leaks. I assumed it was vacummed and didn't leak. I'm going to call them and ask what there statement meant that they did. THANKS RAY M