2000 Ford Mustang 3.8 liter 6 cylinder
The AC clutch in the mustang went bad about a year ago so we took it out and installed an idler pulley in it's place until present. Went to Advance Auto Parts today and bought a new AC compressor. Vacumed out the system before I added R134. The vacum was holding rock steady at around 19 Hg. No leaks in the system. So I turned on the car and put the AC on Max Cool full blast and noticed the clutch did not come on. Figured it needed a charge so I added 134 and it took a charge real good with that vacum in place. So the clutch finally came on but now it's short cylcling. It only stays on for a like a second or two and switches back off. The pressure rises to like 55psi then the clutch cuts on for a second and the pressure drops quickly to like 20psi with the clutch on then the presssure rises again to the same thing like around 55 psi (almost in the red zone according to the gauge), the clutch comes on for a second, pressure drops again rapidly then rises back up. Over and over.
When I was installing the compressor I didn't realize it was full of oil and when I tipped it down to get it on the mount most of the oil in the compressor spilled out. I've found that the auto parts store carries ac compressor oil that can be added through the low pressure port. I don't think that's the problem though. I thought maybe the pressure was too high so I let out a bunch of 134 till the gauge read around 30 psi and so the clutch would come at the high point of 30 psi, drop to like 10 psi, clutch would cut off then it would rise back up to 30 psi and do it all over again. I added and discharged 134 back and forth and tried out different pressures but no luck. Still short cycles. One thing is consistant though. When the clutch does come on at the max charge I have in it, it drops consistently around 20 or 25 pounds from the high point then rises back up again. If I got a 55 psi charge in it then it drops to like 30 psi before it rises again. If I got a 40 pound charge in then it will drop to like 15 psi before it starts to rise again. Anyone got any idea what it might be? The pressure switch?