The valves on the manifold set remain Closed when evaluating a system The high side valve should stay closed any time the compressor is running.

Test the system with both valves on the manifold closed. Run at idle & record the pressures & the ambient temperature. Post the results.

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Your system started out short cycling with high pressure on the high side. A few days later it is short cycling even worse, and the high side is 100 psi lower. It has a leak. You had enough refrigerant in it at first to see 240 psi @ 80F ambient at idle a 3:1 P/T ratio that says poor condenser perfo...

On a 12 year old vehicle with a major part replacement we generally replace the dryer at the same time.

It looks like your system has a leak. Your pressures & cycling indicate it is low on charge.

Again, how much oil was added when you replaced the condenser?

There are a couple of switches & sensors, but looking at your pressures those appear to be working. The thing that sticks out in your post is very poor condenser performance for those low ambient temperatures. Generally we would go right to blaming the clutch fan for that. Your Super Duty has th...

Yes, C5's had the V7 compressor. They also use the ACDELCO 1530851 manifold that sends the discharge line toward the front of the car. A V7 with a bare snout & a belt clutch for it sounds like a good place to start. As for the forum, we discuss car stuff here. If there is a problen with our disc...

Is that at idle or with the engine at 1500 rpm?

A thermometer really helps. The ambient air temperature tells us about the condenser. The vent temperature is also important.

Looks like a lot of overlap, and that exhaust closes real late for an economy cam. Looks like 45 degrees of overlap & 112 degree LSA Would be good for 36-38 inch primaries on the headers & 6000 rpm While there is nothing wrong with an LS, engine swaps are never easy or cheap. There is always...

For heater valves on GM stuff I use a vacuum unit, like the AC Delco P/N 155536 It was used on G vans, and P vans from 1990 to 1996.

There is a 4 port valve on the 03-04 CTS as well, it is vacuum with a solenoid valve.


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Leaving the check valve alone is a great plan. Too often people get carried away, and assume it is a regular tire valve... You can flush the POA with a light oil & plenty of dry air. You will be flowing through it recalibrating anyway. Since docs blocks has been out of business for a while, I be...

POA valves. Be gentle with the schrader valve on the oil return line at the POA body. It is not a standard schrader - it is a special low cracking pressure part & they are getting hard to find. It is used as a check valve to let the oil in the bottom of the evaporator bypass the POA when the suc...