Automotive Air Conditioning Information Forum (Archives)

dorisg1 on Wed July 17, 2013 1:36 PM

Year: 2006
Make: ford
Model: mustang gt
Engine Size: 4.6
Refrigerant Type: r134a
Pressure Low: 350 psi
Pressure High: 210
Country of Origin: United States

just replaced compressor, accumulator and orifice tube. Vacuumed system down overnight with Yellowjacket 4 cfm pump. Vacuum holding fine. Hear is the problem. On start up from cold, low side reads 350 psi - high side reads 210 psi and very cold air coming out vents. After driving half our or so and cutting ignition off and restarting the car, compressor cycles every few seconds with gauge reading 35-45 psi high 200-210 psi. Replaced low pressure cycling switch to no avail. I did install a variable orifice tube could this be the problem? I didn't flush the system because it looked clean. Reason for servicing was do to a compressor leak. Any help would be greatly appreaciated.

webbch on Wed July 17, 2013 2:57 PM

Something doesn't jive here. On startup, you claim low side reads 350 psi, yet you're getting cold air out the vents. Those 2 ideas are mutually exclusive. Must be an equipment issue, likely an issue with getting the core depressed on your gauge set. You also don't mention temperatures, so it's hard to make out too much from the information provided.

iceman2555 on Wed July 17, 2013 5:18 PM

No way in heck can one have a cold low pressure line with pressures that high...ain't gonna happen...never...no way. Agree either something is wrong with the gauges/service port connections....something.
Why do you think the LPCO is the problem with the compressor cycling....could it not also be a possible high side restriction and the resultant high discharge pressures causing this.
From the repair, it appears that the system could have a restricted condenser...this could cause a rapid cycling situation. Operate the vehicle for a few minutes and test the temperature of the discharge line (compressor to condenser) to determine if the temp gets hot...very hot....like not going to touch that line again. If this line temp begins to slowly increase in temp after compressor engagement....bring the RPM up to about 1200-1500 and retest line temp.
Let us know what you discover.

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