My AC Compressor Clutch keeps engaging and disengaging. Whether the AC is on or not, it will engage for a few seconds, then disengage for about a minute, then reengage for a few seconds. Is it supposed to do this? My AC has been good and cold for years. I would think if I had a leak or something causing it to not stay pressurized, then it would have leaked out all of the AC refrigerant by now. But what do I know? I am by no means an AC expert! Is there a sensor or something I should check? Would it do me any good to replace the AC compressor? It's kind of annoying the hear the clutch engage and disengage all the time, and to hear my idle change slightly as it does so. Thanks.

 

cycling is due to low freon. typically about 1 to 2 ounces leak out per year due to the high pressures. but, the thing that concerns me is that you say it does this whether the a/c is on or not. something tells me that the compressor has power to it all the time.

 

Right, it needs Freon.

You must have the selector lever in Defrost; that's actually an A/C setting.

 

Spitz,

There are a few possibilities. What's the weather like where you're at?

First, as you've been reminded, the AC compressor will operate in MAX, AC, BI-LEVEL, and DEFROST modes. If it is operating in any other position, you likely have a problem with the function switch.

The reasons the compressor can cycle are usually related from abnormal system pressure:

1. A loss of refrigerant will obviously lower the system pressure.
   
2. Low ambient temperature will also cause a low system pressure once the compressor cycles on.
   
3. Clogging in the condenser from oil contamination can create a high pressure, shutting off the compressor.
   
4. A restriction in the expansion control/orifice tubes will cause a high system pressure, which will also cycle the compressor off.
   
5. Debris on the condenser can create a high pressure, cycling the compressor off.
   
6. A clogging evaporator can create a low pressure in the accumulator, which will also shut off the compressor.

The best procedure is to connect a gauge set and check system pressures at a known temperature. It outdoor temperature is below 50°, the compressor cycling will be normal with an R-12 system.

So, what's the weather like there? We've got a good chance of flurries here today, so anything is possible.

 

WOW VADER!!! Did you design the thing for GM or what? You seem to know it inside and out!

As for the weather:

"It's Hot! Damn hot! real hot! It's so damn hot you can cook things in your shorts! You know what I'm sayin'? Do a little "crotch-pot cookin'"" From Good Morning Vietnam, the movie.

Seriously though, I'm in Nashville, TN (a.k.a. Nashvegas, or the ville), and it's pretty warm already (in the 70s). It sounds great now, but August is rough!

I'll check the pressure and charge the freon the next time I'm home. I'm away at school and therefore away from my shop. I thought if the AC was really good and cold it meant the freon was O.K. But, apparently low pressure will still cause it to cycle my compressor on and off, even if the AC is cold. Maybe someone can tell me how to clear the components of any debris that may be clogging the system?

Thanks for all your help guys!

Spitz.

 

to clean the insides, you'll have to evacuate the system, pull the orifice tube out of the lower evaporator line, clean it. flush the system to get the contamination out of the system. might as well replace the accumulator if you do this.

little known fact, but the recommendation is to replace the accumulator every 3 years. it's job is to absorb moisture in the system. once the dessicant bags are full, then it can't remove any moisture. the lean the outside of the condensor, the thing in front of the radiator, just run a hose over it. pressuring the water to push out all the road debris.