I had my AC repaired a couple of years ago and this year, it is not cycling off and on. I had all lines fluched out as well as replaced the compressor, orifice tube and dryer. Is there anything other than the compressor that can cause this ? If so, lead me in the right direction for troubleshooting. It doesn't seem to cool as good as it did last year so I could need a little freon. Would it being a little low cause it to not cycle off and on ?

Thanks for the help,

 

If I get what you mean by cycling on and off, then you may also wants to check the wiring to the compressor. Thats what engages the clutch on it and drives the freon.

 

If the system is low on refrigerant, the compressor will not kick on.

If the system is full and the compressor won't kick on, then you have some sort of electrical problem.

BTW - when you say "not cycling," do you mean that the compressor does not come on at all; or that it comes on and stays on (never goes off)?

 

The compressor will not cycle if you are low on freon. You can perform a simple test by unplugging the electrical connection going to the drier and using a piece of wire as a jumper on the plug. This will cause the compressor to engage. If this doesn't cause the compressor to engage, you probably have an electrical problem instead of low freon.

 

I always called it cycling when it would go on and off, but yes, that is what it is not doing. It is staying on at all times. I will try to jumper the plug before I go get it checked for freon being low.

Thanks for the quick responses.

 

Staying on all the time can also be caused by improper refrigerant level.

However, there is a thermostat somewhere in the system that tells the compressor when to cycle on and off. At least there was in the last Ford AC system that I rebuilt. It is adjustable, so you can make it leave the compressor on for longer or shorter periods. If this went bad, it could cause your symptoms. But before you pursue this angle, make sure that your system has one of these thermostats somewhere. I would think that every ac system has one, or else how would the compressor know when to turn on and off?

 

There's no thermostat - the low-pressure switch is what causes it to cycle. If you unplug it, the compressor WILL shut off unless the clutch has seized.

 

Steve, it might be helpfull if you could label a few more things in that picture. Like, what's that twisty looking thing in the upper left corner?

Good lord, how long did it take you to do all that?

 

Just a few minutes.

And the technical name for that twisty thing is a "thingamabob", not to be confused with the crooked "thingamajig".

 

Thanks for the pic Steve. I replaced the pressure switch last night because mine had a small crack in it but I don't know if it was big enough to make a difference. Today on the way home, I'll see it it cycles or not. If not, I am going to get it charged somewhere. Too bad I didn't buy a case of the liquid gold many years ago before they quit selling it. Oh well, thanks for the info. I will unplug it tonight and see if the compressor cuts off.

 

I wasn't sure of the thermosat. I had one on my 72 F100. It was good in that it was adjustable. I could control how long the compressor ran befor it cycled. I adjusted it to keep the compressor running long enough befoe cycling to keep it just this side of freezing. My AC was blowing 35 degrees in hot Miami. I think the Bronco with R134a blows closr to 50, which is ok, but 35 will freeze you right out!

BTW - the ac gets colder on the slowest fan speed. The air stays longer in front of the cooling fins so it cools better.

 

Lets not confuse temperature with heat transfer...
You will get the coldest air on the slowest speed, but you will remove more heat from the air at higher speeds because the volume of the air increases more than the temperature rise.

Please don't flame me for this :-)

 

GR8Diesel is right - heat transfer is more important than air temp at the dash register. With high speed, the AVERAGE temp inside the cabin will be lower, even though the outlet temp is higher.

And ALWAYS use "MAX A/C" - never "NORM". Max recirculates the air, which is cheaper and more effective.