Automotive Air Conditioning Information Forum

This is a 2005 Lincoln LS, and I decided that I only wanted to do this job once, since the dashboard needed to come out to replace the THX valve. I replaced the compressor, THX, evap, condenser and the filter/drier. Essentially I had a brand new system, all the components were new, BRAND new. I flushed all the lines several times with solvent flush, blew them dry-they were clear. I replaced every o-ring in the system. I made sure that I had added seven oz of PAG46 oil (after I drained the oil that the compressor shipped with). Three ounces in the compressor, and the rest was added to the other components. Once I got the compressor installed, I spun the shaft about a dozen times so that the oil would not slug the compressor upon startup. By the way, there was no debris in the lines, my old compressor began to leak oil, but I stopped using it before it started to throw off any metal shavings.

I vacuumed the system down for 45 minutes, and let it sit for a couple hours, and it held the vacuum perfectly, NO leaks. Using a high/low gauge set, I tried to charge with the car running, on the suction side, as a gas (30lb cylinder using a professional gauge set). The compressor would not kick on. The low side pressure as I attempted charging would only read the static pressure (about 80psi). I’ve charged many systems before, including this vehicle and never had one that would not kick the compressor on by charging as a gas through the suction side service port. I even jumped the clutch relay, and the clutch engaged but still would not suck gas. Well, I’m willing to learn, so I spoke to a couple coworkers who service AC systems and they told me to charge enough as a liquid on the high side with the engine off to get the pressure switch to close. So I did that (engine was off at this point). Turned the gas bottle over to further charge as a gas once I started the engine.

Started up, clutch engages, the gauges do not move…high side at about 120, exactly where it was when I stopped charging the high side as a liquid. Low side at about 80. Compressor clutch never disengages, never cycles. I double checked and triple checked all my work, everything else is perfectly intact. I’m a biomedical engineer and work on medical life-support equipment, so I’m pretty thorough and very careful, neat and organized.

Given that these gauges do not move, don’t flutter, don’t bounce off the initial charge readings, I can’t reach any other conclusion than that the compressor has a failure. I know that the chances that a new compressor will fail are low, but I can't reach any other conclusion. Not a Motorcraft compressor, so it's entirely possible that this part could be a dud.

Do you have any suggestions, or would you concur that it appears the compressor has failed? Thanks for taking the time to read this long explanation.

One can only hope you have shut off the valves on the gauge set after charging-- otherwise you have created a bypass through the gauge set.....

Indeed I had. Never charge both sides at the same time.

I wish I had done something stupid like that, so I could just do a forehead smack and move on!

Problem solved...there was an obstruction in the low pressure line between the gauge set and the suction port, so none of the gas was reaching the compressor when I tried to charge the system. That's why it seemed as if the compressor wasn't...compressing, because it was not getting any refrigerant.

The obstruction was that the line fitting was tightened down to the gauge set so tight that that the seal ring was squished flat. It just didn't seem right that the compressor would fail the way it appeared.

I kept staring at it, thinking that it HAD to be something simple that I was overlooking and then began to check the schrader valve on the charge port and then the connection to the charge port. Eventually, I worked my way back and found it. As soon as I loosened that fitting just a quarter turn or so, refrigerant flowed, systems charged and all is well, pressures are right where they should be.

Cool again.

Good to see you fixed it.Thanks for posted the update.