[turkeyman]

Put a new compressor on my M3. Have also put on new expansion valve. Pulled a vacuum for 1 hour. Put 10 cans freon in. Didn't get cold. Dealer told me to check for leaks. Pressurized system with Nitrogen at 125 psi. left set for 1 Hour- didn't move. Pulled vacuum again and put in 4 cans- when adding freon the guage goes up to 40 psi but when can is empty - goes to negative. High side running 130 psi. after 5 cans(even at 10) I still have a negative pressure on suction side. I then took of hose and sure enough I still have a vacuum on the suction side.
And no cold air- if any one has any clue what could cause this I would really appreciate it.

 

[jbirnsch]

If you have no leaks then maybe the air dryer/filter is plugged. I believe it uses a york rotolock style pump. They come in LH and RH suction so make sure that you got the right pump. I have had new pumps that were bad also.

10 cans of R134a seems like a lot. Normally when converting a R12 system that you charge to 70% of what the system requires with 134a.

 

[belfordwest]

Try washing out the coils on AC. They could be plugged up.

 

[nddan]

I think by the time the M3 came around the manual on off valves on compresser fittings were gone so I don't suspect you have them turned the wrong way. What I do suspect is the receiver drier has failed and beads likely floated down the line plugging hose between drier and expansion valve. First thing I would do is replace drier and remove hose between drier and expansion valve. There would be a fitting at bottom of cab door that should be also disassembled. Sounds a whole lot like a restriction where compresser can not get anything to compress thus very low flow. Good luck