A/C clutch HELP Guys!!!

[Rob Benham]

Hi...I've been away from this forum for a long time....most of it spent trying to get my MB E500 Sport fixed. LOL, never paid so much for a car, never had so many 'Put it on the back of a truck and take it to a dealer' type of messages.

If I want to know I'm going to complete a journey, I take the old Caddy.

Anyway, I do have a problem with my old FWB. 1995, model, it runs well, but the A/c clutch is not going in. Long story short, I find that I've got 12v at the clutch, and the current across the relay (with it removed) is 3.3 amps. About right for the skinny wires that are going into the clutch I would guess.

Anyway, sometimes it goes 'Clunk' and the compressor runs, but most times it just does nothing. I can hear a very slight change in engine note as I bypass the dryer switch...this is the 3 amp load on the alternator I suppose. Nothing else, no click of any sort. Funny it should work sometimes.

I was dismayed at the cost of a clutch, $140 ish from O'Riely's and 107 on the net. But...it looks like a problem to get the clutch off. Anyone done this?

I see in the center of the clutch, a threaded shaft and a ring round it with a punched flat, or maybe a pin. Can't tell. Anyway, no nice big nut to undo.

Is this how it's removed from the compressor? Can it be done without de-gassing?

This looks a bit tricky, but I don't want to de-gass if I can help it. Here's the reason.



Took a long time to go through all this.

[jayoldschool]

Nice gauges, and nice vacuum pump! Harbor Freight?

Believe you do have to evacuate. There is a seal on the front shaft of the compressor. I'll take a look and see what my FSM says, though. I'll be back in a bit...

[Rob Benham]

Thanks for looking.


No the kit was from AutoZone or some such. Pay full price with 100% refund when you're done. No pressure to hurry either.


The thing is that the new compressor and clutch is not much more than the price of a clutch. $50 ish. more I think. But having to do all that work again seems tedious to do it a second time round if I can get the clutch off in situ.

Rob

[Rob Benham]

Huh! Here's a thing.


I wanted to make sure about my thinking, so I had another look today. Sure enough, 3.3 amps was pulled when an ammeter was put across the relay terminals. 3.8 amps when on charge.

I disconnected the clutch plug on the compressor, and checked again. Zero amps. So it seemed fairly certain that the current was flowing through the solenoid coil.

It was about now, with the power on again, that I hit the clutch with a big hammer. It clunked on.

Big hammers were a standard tool in post-war Brittan

I found that it didn't spring out again, so I prized it out, and hit it again. Several time. Now it works by itself.

The thing is that I would like to dry-lube the bit that slides, but daren't do this if I'm going to get graphite on the clutch surfaces.

Anyone have an exploded diagram of the inside of the clutch?

[carnut]

The clutch coil is an electro-magnet, If the magnet is weak, then its hammer time!! Also if the air gap is too wide between the coil and clutch, the current cannt span the gap and again, hammer time. The clutch comes off with a specific puller. A spanner wrench of sorts that prevents clutch rotation as the puller threads into the clutch face. The system does not need evacuation to replace the clutch assembly. Shops will normally replace the compressor as an assembly to lessen comebacks and also to be able to warranty the assembly rather than just the clutch. The other rationalle is the compressor's as old as the clutch and why do it twice too soon.

[Rob Benham]

The clutch comes off with a specific puller.

Yes, I can see a thread in the front hole, and a thread on the center shaft. It's the locking thing I don't understand. Maybe, the lock is just a punch mark, and this would be overcome with a special tool. However, as of tonight, the darn thing is still going.

I wondered if there was a buildup of debris between the pulley and the front plate. Hitting it would perhaps of crushed the dirt out of the way, and then the magnetism would have been strong enough to keep it in. I could be clutching at straws. (Geddit) But hey, this would be a cheap fix if ever there was one.

Thing is, that fixes like this don't often last, so I'm still interested in getting it right. But without a diagram I'm kind of working blind.


Rob