1993 240 intermittent air. When it runs. it runs cold. However compressor will turn off and right now will not go on at all.

I checked for 12V with a vom right at the point where the green wire goes into the clutch/compressor. There is always voltage there, so is it safe to say that the a/c clutch is bad? I can spin the compressor with my hand.

Is just the clutch replaceable? Or do the shops normally swap out the entire compressor?

Thanks for your opinion!
--
1993 240, 1992 240GL, 1985 240DL Wagon, 1983 240DL

I agree with aleekat, make sure your ground wire is where it should be, I know someone, do not ask me who, who did this dance with a loose ground wire for the clutch.

Good Luck
Fred

Ok, just removed ground wire and ohmed out perfect. Just to be on the safe side I soldered a sister wire to it in case there is an intermittent break in it. Reinstalled, coompressor does not come on. WIth vehicle running I used my vom and checked the green wire directly where it goes in behind the clutch (somewhat dangerous) and there is 12 volts there!

Why won't this darn thing come on?

If I apply 12 volts directly from the battery to the hot wire then the compressor comes on!

Very confusing to me, what the heck am I missing???????
--
1993 240, 1992 240GL, 1985 240DL Wagon, 1983 240DL

You aren't missing anything, the reason the clutch will not come on is either the wire or the coil can not flow enough current to attract the clutch plate to engage it. One strand of the multistrand wire can give you enough current to have your meter read 12V, but cannot flow enough current to energize the clutch coil enough to pull in the clutch plate. You could also have shorted turns in the coil which could increase the current slightly, but not enough to pull in the clutch.

If the above fails, give the single pin connector on both sides a tug apart to see if the wire slips out of its crimp. I had one bad crimp that made contact but dropped the voltage from 12.9 to 9.7 V.

You could use an ice cube relay and fused line from the battery plus to provide the coil voltage and use the coil voltage wire to energize the relay. This is a good solution when the vehicle wiring has unneeded current drops. This will also help the clutch last longer as it assures the full pull into the driven plate.

I thumbs up you as you are right on target as what is most likely happening.

I would like to note that burned contacts in a relay can do the same thing as the lonely strand of wire.

Phil

Yes clutches can be replaced if you can find someone who sells them seperately as most want a clutch and compressor assembly.

Before you pronounce the clutch dead, look to see if the clutch plate has a red tinge indicating heating. You gap them with a flat feeler gage and shim washers. Some need special pullers and snap ring pliers to get the plate and coil assembly off-- others just use bolts and screws.

Also, based on a recent episode, a new compressor and clutch worked fine when jumpered directly to 12 V, would not work on the 12V on the connector like you have. The mechanic gave up, however, I later found the compressor side wire pin had a bad crimp that would make with the test clip and not make plugged into the socket. Use an ohmmeter and a safety pin through the clutch coil wire close to the coil to see if it is open as shorted ones smell and blow fuses.

Sounds like it could be low on freon.
Dan

Dan:

If it was low on freon, wouldn't a sensor switch of some sort automatically turn off the 12v to the compressor? Also, when the compressor decides to come on, the air coming out of the vents is super cold, doesn't this also rule out "low freon"?
--
1993 240, 1992 240GL, 1985 240DL Wagon, 1983 240DL

Unplug the hot lead to your compressor. Engine off. Jumper 12volts straight from battery to compressor, clutch should engage/click. If no sound, clutch or field coil has gone bad. Verify your ground on back side of the compressor is not loose or has come off.
--
Post Back. That's whats makes this forum work.

I checked for presence of 12v directly where the hot wire goes into the compressor(right behind clutch). There is 12v present and the compressor does not turn. Why would jumpering 12v from the battery be any different, if my VOM shows 12v at the hot wire already?

Thanks
--
1993 240, 1992 240GL, 1985 240DL Wagon, 1983 240DL

You are bypassing the entire a/c system/relay/circuit board by putting a direct 12v to the compressor. Notice I say car off, key off. Check that ground from(normally at a mounting bolt) either to the bolt or under the manifold/throttle body.
--
Post Back. That's whats makes this forum work.

Try bypassing the switch, if the compressor goes on the freon is low. Just don't run it that way too long.
Dan

Dan:

If the switch was bad, would I still have 12v at the compressor? I have 12v at the compressor and the it is not engaging, wouldn't that mean there is an issue with the clutch?
--
1993 240, 1992 240GL, 1985 240DL Wagon, 1983 240DL

Have you checked the ground for the clutch? It is grounded by a separate wire duue to the compressor being mounted in rubber bushings. If there is no ground the compressor will not run.

Bob-- I applied 12 volts directly from the battery to the hot wire going to the compressor and the clutch kicked in, wouldn't that rule out a bad ground to the clutch?
--
1993 240, 1992 240GL, 1985 240DL Wagon, 1983 240DL

Problem with A/C was fixed by repairing leak and recharging system-$140.00
--
1993 240, 1992 240GL, 1985 240DL Wagon, 1983 240DL

Spoke to soon, a/c went out again today for about 20 minutes, then came on again. Back to the shop on Monday
--
1993 240, 1992 240GL, 1985 240DL Wagon, 1983 240DL

It was the clutch as I suspected! I brought the vehicle back in and spoke directly to the mechanic. I told him that when the a/c was not working I checked the green wire right where it goes into the clutch for 12v. He looked at me and asked me if I had 12v and I told him yes. He said no doubt about it, clutch was shot. He replaced clutch and a/c has been working.

Thanks for the advice here. And it always pays to talk directly to the mechanic because I did let the "check in" guy at the desk know about my troubleshooting and he did NOT pass the info onto the mechanic.
--
1993 240, 1992 240GL, 1985 240DL Wagon, 1983 240DL

Yep, it paid! He did not have to CLAIM to you that he checked for other things during his 75 dollars an hour shop rate.

Good on ya! Thanks for the feedback to the board too!

Phil

$75 per hour shop rate, I wish, try $95 per hour!
--
1993 240, 1992 240GL, 1985 240DL Wagon, 1983 240DL

What switch-- the one on top of the receiver/drier unit?
--
1993 240, 1992 240GL, 1985 240DL Wagon, 1983 240DL

That is the one.
Dan