Ford swaps with working air conditioning, have a few questions
 

My swap is nearing completion, and i’m working on the a/c now. I spliced in the Ford compressor from a 01 Mustang GT using the MMR swap hoses, using Esther oil and 134 refrig. I am using Martin’s rad and fans with a custom shroud that I built. I have it all charged up, and spliced the wiring so when I push the dash button it engages both the fan and clutch. I have run it and I have ice cold air, and after idling for a good 20-25 mins on a mid 70s day, with the coolant temp hitting roughly 230, my cold side press is around 30 and high side around 170. The issue seems to be that there is no cycling of the compressor, is is just constantly on, which I think is leading to the higher coolant temps, there is no break in the load being put on the engine. I have the condenser sealed tight to the rad (you can feel the suction of the fans if you put your hand in front of the condenser). My question is, for those of you with working A/C, does your clutch cycle, or is it constantly on? Is this something that I just have to get used to manually controlling, or is there something else I can do? I throw the pressure switch is more of a safety, and I don’t think it will kill it until hot side is much higher. Is there something else on the evap side that should turn it off based on temps? Just trying to make sure i’m not missing something.

Thanks!

I have mine working - 93 mustang compressor and MRM swap hoses. I also used an engine wiring harness modified by Jason and I made the ac electrical connections as per his instructions. I don't remember what my low and high pressures ended up being, but my clutch did not cycle at first. I had to add more refrigerant. I may be mistaken, but I believe the clutch cycling is based on pressure only. Is it possible that your wiring has bypassed the pressure switch?

It is probably not going to cycle at idle. Try giving it a little gas to about 2000rpm. It should cycle when your low side pressure drops to around 24.

It is possible that I spliced around the switch, i’ll Have to double check. Not sure what psi the switch is supposed to disengage the clutch at, anyone know? I initially overfilled it and saw 300 psi high side and it never disengaged. Now I have the pressures around the factory spec, and the clutch stays engaged and the pressures pretty consistent over a long running period (both slightly increased as the car warmed up). Is it possibly an issue with my compressor not building enough high side pressure? Like I said, the air is ice cold and the pressures are both where the factory manuals say they should be, I just worry about the compressor not cycling off keeping the load on the engine and possible overheating based on no “down time” from the load.

My low side is higher than 24 at idle and the compressor is constantly on, not cycling off.

Increase rpm's to simulate a "driving condition". As the high side pressure increases, the low side pressure should decrease. It should cycle at around 24. It will probably never see enough suction on the low side at idle to ever cycle.

Ok, i’ll try that when I get back in town. Thanks!

Ok, back home and messed with it. Found one of my fans was not working, A/M relay failed, replaced it and now have both fans and cooler temps again. Took a vid of it running at temperature with ac on full cold/high fan. Compressor is on whole time, never kicks off and you can see where the pressures are at idle and how they change with revs. Air is coming out nice and cold, and I checked my wiring and I spliced in to the green wire side of the pressure switch, so it should not be bypassed. Here is the vid (sorry about quality, was holding phone with one hand and trying to hit throttle with other):


any thoughts why it does not cycle? Am I maybe light on charge?

I've messed with it some the last few days after doing more research, and added a little more R134 to get the pressures up a bit, and it is blowing out pretty cold and the pressures are moving as they should, it's just not turning off at any time. From what I can tell, the switch that will turn it off is a temp switch on the evap core, and if it does not get cold enough, the compressor will stay running. I am thinking that it is just not getting cool enough while sitting still and not driving. For now I'm pulling off the gauges, and putting the car back on the ground and am going to just run it as is and see how it works. i did notice a small leak at the schrader valve on the Ford compressor, tightened it with my tool, and then remembered that I have conversion fittings laying around, so I popped that on there and it should be fixed. I'll keep an eye on it. Fingers crossed!