78 Dodge A/C

[ELCBOSS]

I am having ac problems. The ac on my 78 dodge motor home 440 cid has had several problems in the past. compressor has been replaced along with several other components. Just recently replaced a suction in line filter and yet pressures still will not come in to right alightment. Suction line pressure after only two cans freon sits at 35. High side 250. very hard to fill system to right amount. With all this the suction side on the head is 10 psi. should the two low sides not be close to the same. My only thought at this time might be to factory filter if that is what it is in the hose, or maybe the valve (can't think of the name) in the suction side of the compressor itself. Any help will be appreciated. Also new new filter drier and expansion valve a couple of years ago. Thanks. Larry in Texas

[alloro]

If you're getting 35 psi at the low side port but only 10 psi at the head, then you do have blockage in the suction line between the port and the compressor.

When you evacuated the system, what did you get the vacuum down to and for how long did you hold it there?

[ELCBOSS]

When evacuating system I pulled it down to -28 and it held that for four hours. Another item I forgot to mention. This being an older unit, it has no cycle switch. Low side is controlled by EPR valve in suction side of head which might make some sense of pressure differances.

[mazdatech177]

your pressures both seem a little on the high end... make certain you havent
over-charged the system and that the thermo fan clutch is working properly

[alloro]

Originally Posted by ELCBOSS

Low side is controlled by EPR valve in suction side

Sounds like it's sticking in the almost closed position and not allowing the freon to pass through. Just out of curiosity, is this an R-12 system or has it been converted to R-134a?

When you were pulling vacuum did you have both the high and low side valves open on the manifold gauges? My best guess from not be able to have my hands on the vehicle, sounds like you had the high side closed off and with the low side being blocked by the valve, the result was not all of the old freon and oil was pulled out.