300SD R4 Compressor Clutch Issues
 

Hey everyone,

My dad's 300SD seems to be having some clutch issues on the R4. The R4 is--I think 3-4 years old now.

The clutch seems to kick on sometimes and other times not. If I give it a tap with a screw driver or pipe it will kick on..

Is there anything I can do for it?

Start simple-

Have you checked the pressures with gauges? It could be around the low pressure cut out and cycling on and off due to that.

Then make sure the connection on the compressor is solid and it is getting voltage.

Once those two are confirmed I would then delve into the compressor.
(Perhaps you already have checked that and just didn't mention it :o )

Check the wires. The R4 electrical connection can be tricky to properly hook back up. The spade connectors have a spring-action, but it's easy to miss this and get a pressure fit between the plastic housing and the connector.

I think, but can't guarantee, the coil on the clutch should ohm out at around 4. If the clutch is getting good voltage, but won't close, they can be replaced. I have a spare pull-off on my garage, yours for the cost of shipping (>$10, I'd guess). It was working when I pulled it.

I connected up my manifold and the pressures I got were good. The high side was near 150 Psi.

The clutch is definitely getting power, I figured I'd see if the connections were loose and jiggled them with my long screwdriver. Accidentally tapped the positive to the frame--SPARKS. But yes its connected fully.

I would surmise that if it was not getting electricity me tapping the front of it would not engage the clutch fully.

How difficult is changing the clutch on these R4's? Can it be done on the car? I've never done any work with the compressors.

Yes, it is getting voltage, but if you put a multimeter on it you will be able to tell if the voltage is constant. There is a chance there is some electrical fault giving an intermittent signal but it does seem like something with the clutch is acting funny. I've never changed one so I'm no help there.

The gap between the pulley and the clutch plate is probably too great. I don't remember the specs but between .010 and .005 should be fine. There should be a 1/2 in or 13 mm nut in the center of the clutch disk. See if it will tighten any. You will need to hold the clutch disk with a BIG pair of channel lock pliers or something. If the nut is tight, then replacement of the clutch is do-able on the car with the correct tools. You will need a clutch disk puller, snap ring plies and a pulley puller. Then you will need a clutch disk installer. The snap ring is on the outside of the collar the pulley slides onto. DO NOT remove the snap ring inside the collar, the one close to the input shaft. It holds the front seal in and if you remove that snap ring with pressure on the system, the seal WILL come flying out along with all the freon.

Paul

It can be done on the car. I replaced the idler pully bearing on the R$ still mounted in my w123. You will need to get two different tool kits rent one from Auto Zone and the other from O'Reilly. I do not remember the numbers though. I'll look for my old post and then link it.

Here it is:

http://www.peachparts.com/shopforum/diesel-discussion/291597-82-300d-how-difficult-change-c-clutch.html

Also be aware that this nut is used to set the air gap, it _won't_ " tighten up " like a regular bolt until the plate is pulled fully against the pulley face resulting in the compressor runing full time. Turn the nut only enough to set the gap.

Other brands of compressors use shims on the shaft to set air gap.

Check the voltage across the plug with it plugged in to be sure you are getting full power. You can cycle the clutch with the engine off as it is safer.

If you're getting power, but it's intermittent and closes with a physical rap, then it's possible the coil is cracked or the connections are corroded.

You can remove the wires and connect an ohmmeter to the coil, it should be around 4 ohms, IIRC.

The clutch may also just need a really good cleaning and adjustment. I think the gap is less than 1 mm.

Ill have to climb under it and check it out. The odo/trip just quit today on it too. So I've gotta take the cluster out and see whats up... Its probably a gear, but I hope it something simpler.