New compressor coming on but no ac?

[Quick4door]

I have recently replaced my AC compressor, along with the dryer. I have evac the system for around 30 minutes and injected 2 ounces of peg 46 oil, and 2.2 pounds of refrigerant. The AC compressor is coming on, the low speed fans work, but there is no differential pressure and no cold air. Pipes are not getting cold. High and low pressure sensors are new. All fuses are good (checked). Fan control relay is good. Bm is sending the signal to the compressor so it’s good.

Is this a bad compressor?

 

[gsxr]

If the compressor is running but there's no pressure differential.... that sure sounds like a defective compressor.

New Denso compressor, made in Japan?

 

[Quick4door]

Was the GPD brand on rock auto- mine is the 8 rib which is quite hard to find. Everything I find from Denso or for my car specifically is 6 rib. This is a compressor for a 96 SL600 which is identical. Only issue is that I purchased this 2 years ago and just now put it on.

 

[Quick4door]

It’s the second compressor in a row I’ve installed that didn’t work. This is a 4th car that doesn’t get used all that often so no ac was not a huge issue. I’ve confirmed everything else works properly but the odds of two in a row? I mean, it’s possible but unlikely. However, proof is proof.

Compressor clutch engages when it’s supposed to and turns off when prompted. Unplugging the low pressure switch makes it turn off, same with the high pressure switch and the fans. I don’t see a reason to replace the BM, or the push button assembly since it’s working.

 

[gsxr]

I'm seeing this for the 96 SL600 GPD compressor at Rock:

https://www.rockauto.com/en/moreinfo.php?pk=3911760&cc=1195950&pt=6628&jsn=2

That looks similar but not the same... it does not have the tach / speed sensor on the rear. I'm really not sure if this is compatible with the W124.034/036 chassis. Also not excited that it's full aftermarket, made in PRC.

I think the pulley/clutch assembly can be swapped between 6 and 8 rib compressors. If so, that means you could buy the Denso 6-rib compressor #471-1227 (link) for 93-95 034/036, and swap on your old/existing 8-rib pulley+clutch to the new Denso compressor. So far, I don't think anyone has confirmed this? The same question has come up several times over the years.

Another option is to convert your 1992 eight-rib engine to a full 6-rib setup with automatic tensioner (details here). Need all the 6-rib pulleys plus the tensioner and AC bracket. Best sourced from a junkyard car so you can get everything cheap.

Again, I am assuming the compressor remains engaged and there's no pressure differential when engaged.

 

[gsxr]

BTW - detailed photos of the 6-rib Denso and OE compressors are here:

Index of /images/M119/AC_compressors

 

[Quick4door]

I purchased the GPD unit from rock auto- it says it is a nippondenso unit. I need 8 rub and these are exceedingly hard to find. It was $450 so it wasn’t the cheapest I could find .

 

[Quick4door]

I’ve gone to so much effort to keep the eight rib. I really don’t wanna have to switch everything over.

That said, yes, the compressor clutch stays engaged when prompted by the push button. If I unhook the low pressure switch, the compressor turns off. If I turn off the high pressure switch, the fans turn off so everything seems to be working properly in that respect. No differential pressure of any kind

 

[Quick4door]

Mine has the switch on the back- the gpd and the oe unit were identical