2003 Merc C240 - Can't get any 134a in the system

[rgnprof]

I found this youtube video that discussed replacing the "clutch hub plate" on these Denso compressors (have to buy aftermarket as Denso does not manufacture this part). I believe this Denso compressor has what's called a Swash plate...

What "faulty control valve" are you referring to?

I just adjusted the clutch air gap on my Subaru, removing 1 shim. But, I don't think this one is the same...

I don't think the 2x2 trick will work here - everything I read suggests that this "clutch" is spinning all the time.

And I don't have a code reader - what one do I need?

[rgnprof]

This is the Clutch Hub Plate:


My Denso compressor is type 7SEU17C.

[Tim]

This is the Clutch Hub Plate:


My Denso compressor is type 7SEU17C.

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[JohnHere]

Clutch or no clutch? Denso literature on this compressor seems confusing.

Be that as it may, for purposes of this discussion: Your unit is a clutch-less, direct-drive, variable-displacement compressor that runs whenever the engine runs—unlike a clutch-cycling system that engages and disengages the compressor according to certain operating conditions.

Without getting into too much detail, the output of a variable-displacement compressor that runs all the time, like yours, is controlled by varying the angle of an internal "swash plate" or "wobble plate"—and hence, the piston stroke (displacement)—by an electronic control valve that is, in turn, typically managed by the PCM or Powertrain Control Module. A control valve that fails can cause problems including little to no cooling and difficulty recharging the system, as you're experiencing.

The control valve located in the compressor can be replaced (they're relatively inexpensive), but Best Practices recommend that the compressor be removed from the vehicle to avoid the possibility of dirt entering the system.

Some auto-parts stores will scan a vehicle for you and report any trouble codes found.

[rgnprof]

Thank you! I'm happy to hear that I'm not the only one confused about this thing!

I went back and checked my records - this compressor was bought new in 2014 and installed shortly after. The previous compressor's pulley blew up on the drive from Oregon to Oklahoma and so the car was not driveable until we could get a new compressor/pulley installed. We never charged it (my son's car) and I don't remember why - he just hasn't used it much.

Could driving it without a charge have caused damage?

Removing the compressor is not that difficult, but I'm wondering if we would be better off to just replace the entire compressor. I have not been able to find the control valve you're talking about.

So there's no easy way to tell (see) if the compressor is actually operating or not??

[tbirdtbird]

Given the new information, I would say that comp is NG. This would have been good info up front.
We assume it had an oil charge from the factory (but maybe not). In any event, some of the oil that (may) have been in there has presumably been pumped out and resides in the hard components, and with a lack of refrigerant the oil has not been returned back to the comp.
It is not worth taking a chance in my opinion

[rgnprof]

In my first post I stated I put oil in it...but yes, I'm not sure about the long term effects of running it without 134a in it.

I don't understand the systems of AC well enough...

[tbirdtbird]

Sry missed the part in post #1 about the oil. The oil doesn't stay in the comp unless it is a sump type comp such as an A6. Few if any sump type comps today.
The oil mixes with the refrigerant and travels around the entire system and that way is returned to the comp. Without refrigerant, the oil is pushed into the condenser, and essentially stays there, there is no way to return it to the comp.
I would not chance it.