Stumped - incessant cycling and pressures all out of whack (video included)

[james89dx]

This is an LS transplant with complete 01-02 Chevy Camaro ECM/wiring/electronics/compressor/pressure switch. We are not using the GM condenser, evap, or expansion valve however. Only thing "custom" are the lines/hoses that my brother and I built which connect the GM compressor to the evap/condenser.

Started with a completely empty system and brand new compressor. Vacuumed for an hour, let it sit for an entire day to verify it held vacuum - it did. Chevy calls for ~ 1 lb 8 oz of R134a. Initially we added 1 lb 4 oz and compressor would only stay on for about 2 seconds at a time, cycle off for about 10 seconds, then turn back on for about 2 seconds. We thought no problem, just low on refrigerant. Added more and more refrigerant and eventually got up to 1 lb 12 oz of refrigerant, but the compressor behavior never changed a bit.

Static pressures were spot on - 65 degrees ambient temp, and both high and low static pressures equalized right at about 65 PSI. However, when you run it, this is all it does incessantly - compressor will only cycle on for a couple of seconds then click off, over and over and over. Judging by what the pressures were doing, we thought absolutely either stuck expansion valve or dead compressor. We replaced both the expansion valve and compressor, vacuumed and charged again and it's STILL doing the exact same thing. This is what it does - any ideas?

https://youtu.be/E2u5kcwRQB4

[Dougflas]

Clear some things up. What vehicle is the condenser and evap from? Is there by any chance still an orfice tube in the evap? You mentioned you tried a new expansion valve but you also mentioned a pressure switch. How about some photos of the system. make sure you step back and include an over all view. I am wondering if you have part expansion valve system and part orfice tube system. Do you have a drier or accumulator?

[GM Tech]

Keep in mind, that a a/c system with a variable stroke compressor that cycles frequently is because of of high pressure cut-outs- most likely- high head pressure is usually due to lack of air flow through condenser, or blocked condenser, --so do your cooling fans work? - your head pressure you see on your gage may not be what the pressure transducer is seeing.

[DarrylS]

sometimes when cobbling systems together you have to just sit down and get a sheet of paper and actually draw out the system in detail. You may find that as others mentioned that your service port locations are not in the right position to get proper readings. The systems are pretty straight forward so do a drawing and identify all components especially the controls......you may need to silver solder in a couple of new service ports!