AC compressor cycles all the time

stevew970 · **Posted:** Tue Dec 01, 2009 3:26 pm

This fall I noticed that my AC compressor cycles on and off all the time, even when the AC button on the dash is off, and even when the heater temp control is turned up. I have an '05 CRD. I took off the part of the dash with the AC button, but the button is behind a circuit board, and I hesitated before taking that off. Is there a way to determine if it is the button or something else that is causing this problem? Seems like it could be the defroster control, how does that interface? I don't want to wear out the AC compressor or clutch, and its a drag on the engine, worse fuel economy, and an extra load on the cooling system. Help appreciated.

Steve

05infernoCRDL · **Posted:** Tue Dec 01, 2009 3:55 pm

steve

your AC compressor will cycle on any setting regardless of the button to the right of 12 o'clock.. it is a fail safe for those who don't run their AC in the summer to keep the compressor properly lubricated. and it takes the humidity out of the cabin air when it cycles.

i see this is your first post... this question should be posted in the "general" CRD section.. the "Tech" area is for upgrade write-ups not general questions.

have a great day and enjoy the wealth of knowledge on this forum

Boiler · **Posted:** Tue Dec 01, 2009 4:28 pm

I've often wondered if the AC compressor being on when the AC is off is the prime culprit to my inability to get better than 15/16 mpg. I almost never run it, but I always get the little puddles of clean water under the jeep during the summer.

If my fan is set to zero, and I'm on a non AC setting, should it still be running? If so, how much? Mind you I drive an 05 3.7 gas liberty. You said it takes moisture out of the cabin, but I fail to see how it would do that if it is not blowing air.

05infernoCRDL · **Posted:** Tue Dec 01, 2009 5:29 pm

Boiler wrote:

I've often wondered if the AC compressor being on when the AC is off is the prime culprit to my inability to get better than 15/16 mpg. I almost never run it, but I always get the little puddles of clean water under the jeep during the summer.

If my fan is set to zero, and I'm on a non AC setting, should it still be running? If so, how much? Mind you I drive an 05 3.7 gas liberty. You said it takes moisture out of the cabin, but I fail to see how it would do that if it is not blowing air.

boiler.. it would take the moisture out of the air when the fan is blowing... other than that it would get any available moisture that happens through the evap... and what do you mean by "fan set to zero" you mean the air deflector is set to "off" which is a zero looking icon? if it is the off icon i would say it shouldn't be running... but fan on 1,2,3,4 it would run if on the floor, floor/defrost, defrost mode

stevew970 · **Posted:** Tue Dec 01, 2009 7:28 pm

Sorry about putting this on the wrong section. So what happens when the heater temp control is turned up? The AC cools the air before it goes through the heater coil? Second question; what happens when the ambient air temp is around 32, wouldn't the AC freeze the moisture in the air, icing up the AC coils and stopping air movement? Enquiring minds etc.

Steve

05infernoCRDL · **Posted:** Tue Dec 01, 2009 9:17 pm

stevew970 wrote:

Sorry about putting this on the wrong section. So what happens when the heater temp control is turned up? The AC cools the air before it goes through the heater coil? Second question; what happens when the ambient air temp is around 32, wouldn't the AC freeze the moisture in the air, icing up the AC coils and stopping air movement? Enquiring minds etc.

Steve

the AC cycles... so the evap. cooler freezes then thaws, freezes then thaws... just like in a refrigerator, that is why you get the water dripping out of the bottom of the truck.. when the AC compressor stops the warm air coming through melts the little bit of ice that accumulates... then the compressor kicks back on and cold freon returns.

the evap cooler is cold, almost always cold enough to freeze water when the AC is running that is how the defrost works.. and i haven't looked at the way the air flows but yes it is probably cooled before heated, but not like it is cooled to 32* then heated to 110*... you can't cool air that fast.. you are just taking the moisture out of it..

and i an not an expert in this area... just spreading what i ahve picked up over the few years of life working in appliance repair places and with my friend in the mechanic shop.

stevew970 · **Posted:** Wed Dec 02, 2009 12:11 am

Thanks for the info. If I get more I'll post it.

Steve

TAHOE · **Posted:** Wed Dec 02, 2009 9:31 am

Funny, I was just wondering the same thing when I noticed my wife's 05 comperssor cycling when it was in heat position. I know they run in AC and defrost, but couldn't figure out why it ran other times, thought something was wrong.

CRDMiller · **Posted:** Sat Dec 05, 2009 1:47 am

My compressor does not seem to cycle at all, it's either on, or off.
Is something busted, or ?

Also one of the first things i did when i bought my crd was modify the ac controls to not operate the ac unless the ac button was depressed.

There's a guide somewhere up here, it's easy easy.
You just snip a wire, and solder in one of your own, inside the controls.

mikey1273 · **Posted:** Sat Dec 05, 2009 2:01 am

mine cycles like that too. I usually leave it in the heat and defrost postition most of the winter in every vehicle I ever had that could be why it does that or so I thought.

I would not want to mod mine so it didn't come on unless I pushed the A/C button. that removal of moisture is a good thing here on the east coast we get more humidity than the west does. doing so may be fine in southern Cali though.

WolverineFW · **Posted:** Sat Dec 05, 2009 2:14 am

CRDMiller wrote:

My compressor does not seem to cycle at all, it's either on, or off.
Is something busted, or ?

Also one of the first things i did when i bought my crd was modify the ac controls to not operate the ac unless the ac button was depressed.

There's a guide somewhere up here, it's easy easy.
You just snip a wire, and solder in one of your own, inside the controls.

Make sure you turn it on once in a while then as the refrigerant acts as a lubricant for the compressor seals. If they dry out your refrigerant will disappear.

jrsavoie · **Posted:** Tue Aug 19, 2014 7:24 am

05infernoCRDL wrote:

steve

your AC compressor will cycle on any setting regardless of the button to the right of 12 o'clock.. it is a fail safe for those who don't run their AC in the summer to keep the compressor properly lubricated. and it takes the humidity out of the cabin air when it cycles.

i see this is your first post... this question should be posted in the "general" CRD section.. the "Tech" area is for upgrade write-ups not general questions.

have a great day and enjoy the wealth of knowledge on this forum

I didn't know there were 2 areas here for CRD stuff. Where is the other area?

flman · **Posted:** Tue Aug 19, 2014 8:14 am

jrsavoie wrote:

05infernoCRDL wrote:

steve

your AC compressor will cycle on any setting regardless of the button to the right of 12 o'clock.. it is a fail safe for those who don't run their AC in the summer to keep the compressor properly lubricated. and it takes the humidity out of the cabin air when it cycles.

i see this is your first post... this question should be posted in the "general" CRD section.. the "Tech" area is for upgrade write-ups not general questions.

have a great day and enjoy the wealth of knowledge on this forum

I didn't know there were 2 areas here for CRD stuff. Where is the other area?

viewforum.php?f=98

sailwa66 · **Joined:** Mon May 14, 2012 9:57 am **Posts:** 32

CRDMiller wrote:

Also one of the first things i did when i bought my crd was modify the ac controls to not operate the ac unless the ac button was depressed.

There's a guide somewhere up here, it's easy easy.
You just snip a wire, and solder in one of your own, inside the controls.

Here:
viewtopic.php?t=6042

Rich · **Posted:** Wed Aug 20, 2014 10:20 pm

darn spam-bots!

jrsavoie · **Posted:** Thu Aug 21, 2014 8:32 am

Most of the threads on vehicles are timeless.

AC compressor cycles all the time

Who is online