AC compressor woes...

[DavidT]

help.
Ford told me that the AC system was 6-8 oz. low on refrigerant... thus explaining the lack of cooling I am getting from my one year old compressor.
So I checked it myself with a gauge. The needle stayed in the BLUE, which means it is charged sufficiently. I don't understand...
I DID notice that while I was snooping around, the clutch would disengage for a few seconds (stop spinning) anytime I blipped the throttle. If I left it in idle, the compressor would run nonstop.
Is that normal?
Also neither the high or low lines would get cold.
Is there a therm. switch or something that could be bad?
Oh yeah, the AC seems to cause the cars voltage to drop quite a bit. This is even with a brand new alternator.

 

[SHOZ123]

I would check the resistance of the clutch coil. Should be less than 6 ohms and the current draw should be 2.5 to 4.5 amps. Also check the voltage there as it should be whatever the current battery voltage is.

Another problem could be the low pressure switch. Check to see if B+ voltage is being passed on to the clutch when working the throttle.

 

[Mr Anonymous]

You have to test the pressure with the compressor engaged. A "full" reading with the compressor freewheeling actually indicates a low charge. With the compressor running it will show low, and once filled with the compressor off it will show overfilled. It's one of the compromises we have to contend with when using the el-cheapo gauge and not a real set of manifold gauges.

You can force the compressor on by disconnecting the pressure cycling switch connector from the accumlator tank, and shorting the two poles on the connector with a paperclip. Be prepared to meter and start filling the refrigerant right after you short the plug and the clutch engages, you don't want the compressor running constantly with a low charge.

P.S. You want to fill it right to the top of the "full" range on the gauge you have.

 

[DavidT]

when I was trying to add refrigerant, the needle would sometimes jump in the red (overfill danger) while it was cycling. It would bounce around at times, and other times it would STAY in the danger area. I was using the R134a can that has a gauge attached to it (Walmart:$20). I wondered if the needle in the gauge was sticking.
So if I am getting a dangerously high level while filling and the compressor IS running, then I have overfilled it, right?

Oh yeah, how often should a properly charged system kick the compressor on and off? Under what circumstances should it do this?
(What causes my compressor to do this upon blipping the throttle while in idle?)

Paul, how hard is it to check the resistance of the clutch coil?

 

[SHOZ123]

Easy to check the resistance of the coil. Unplug it and set the volt meter to ohms. Then check across the two terminals on the coil end of the plug.

 

[ricky]

When checking A/C pressure, make sure the climate control is set on max A/C & temp set as low as it will go. Give the A/C a few minutes to get out the excess heat out of the car. Check with doors and windows closed. An open door/window will add heat to A/C and give an elevated reading. Temperture=pressure.