AC Compressor/Idle question - **updated**

[TwistedCU]

I know when you turn on AC or Defrost (which also turns on my compressor), the idle compensates and bumps up a little. I know this may stop and start as you are sitting idle, but my idle jumps up a little every 5 to 10 seconds or so. This is constant and rythmic. I know something isn't working right. Sitting in a backup on I95 in the rain going nowhere with the defroster on and watching my tach jump every 5 seconds was really annoying tonight. The AC works ok and blows cold.

Is there a way I could put a bypass switch for the compressor? It's kind of annoying that it kicks on for the defroster on a 30 degree day anyhow. Even if I figure out why the idle is so irregular with the AC/Def on and correct it I may still want to do this.

Maybe I should scrap the AC and convert to OBA! - nah, not yet - maybe when I don't have such a long commute :wink:

 

[mingez]

Mine is EXACTLY the same way. Anyone else???

 

[MudderChuck]

bent up flares

You may be experienceing what is called short cycleing. The freon is just low enough for the compressor to run for a few seconds and then the pressure gets to low and shuts down, the pressure goes up and it cycles again.
Open the hood and watch the compressor clutch and/or your aux. fan. You can watch the clutch engauge and listen for the tell tale click.
Might also be a sticky idle motor in the throttle body. A good throttle body cleaning, can help. Various methodes have been discussed. Carefull which kind of cleaner you use, some are plastic eaters. I usually clean mine off the vehicle and remove everything that isn´t frozen solid. The mounting screws can be fragile, have to decide when to stop or you can snap them off. Removeing the idle motor and cleaning the orifice is probably the best methode, if you can get it off without breaking/stripping the screws. Spraying down the thrttle body opening, always makes me nervous, always affraid something might float down and jam a valve open. I usually leave the throttle position sensor on the throttle body, they are too hard to adjust.

 

[MudderChuck]

Re: Rubicon production ceased

Vacume leak is also a possibility, the idle will hunt, if there is a vacume leak. If I understand correctly it only happens, during AC or defrost. Could be a HVAC vacume line leaking. Usually when a vacume leak makes the idle hunt, it´s in or near the intake or a vacume line connected to the intake. Many of the HVAC controls are hooked to the vacume canister, to prevent what you discribe. Vacume lines to the vacume canister, might be worth a look. When the lines to the vacume canister are leaky, it often affects the HVAC controls and the cruise control. The heater AC doors in the heater/AC box stay in the default position, or don´t open all the way. All the heat goes to your feet and little/or no air to the defrost. Or vise versa, different setups have different defaults.

 

[Craig]

Just wondering if anyone knows if the cherokee 4.0L a/c wiring is the same as the YJ a/c wiring. I'm asking because I just hooked up a York compressor and want to wire it to the a/c idle switch so when I turn on the power to the compressor, it will boost my idle. The York works a lot better at a higher idle. I don't have a/c in my YJ but it's wired for a/c. I have the plug near the a/c mount and need to know which wire to hook it up to.

 

[MudderChuck]

Grand Cherokee Advice

Did you used to have A/C in your YJ? If so, it could be as easy as jumping the low pressure switch and hooking up the York to your existing compressor connections (relay and everything should be in there). If it never had A/C, but just has the harness, it will probably need some more pieces and research. At the least, you´ll need to jump the pressure switch, thermostat connections and check and see if the wires are hooked up to your A/C relay plug and the wires are running all the way into the ECU.

 

[XJNick]

Hi,

The only way you could prevent the A/C from comming on with the defrost would be to cut the wire at the climate control head switch contacts for the Defrost Position. Although note that the A/C is part of the defrost because it takes moisture out of the air, thus making the defrost more efficient. :mrgreen:

-Nick :!:

 

[TwistedCU]

Although note that the A/C is part of the defrost because it takes moisture out of the air, thus making the defrost more efficient. :mrgreen:

-Nick :!:

That's why I want to put a toggle switch in there. Compressor - optional!

Thanks

 

[jay79cj7]

Twisted-
My 00 XJ does the exact same thing and I also thought something was wrong. It was the compressor cycling on and off. I thought it was strange, but my buddy's 01 does the same thing too so I stopped worrying about it. If it works, ignorance is bliss. Keep in mind that the compressor runs for the defrost so you don't blow moist air on the windshield and fog it up. There are probably situations where this is needed and others where it is not, so I guess a toggle switch might not be a bad idea.

 

[TwistedCU]

What's a good price for an SYE kit?

Twisted-
My 00 XJ does the exact same thing and I also thought something was wrong. It was the compressor cycling on and off. I thought it was strange, but my buddy's 01 does the same thing too so I stopped worrying about it. If it works, ignorance is bliss. Keep in mind that the compressor runs for the defrost so you don't blow moist air on the windshield and fog it up. There are probably situations where this is needed and others where it is not, so I guess a toggle switch might not be a bad idea.

I knew that it was the compressor kicking on, but I find it strange that it does it so often and so regularly. If that's the way it was designed to work, the design bites.

I also knew that there are 2 main reasons the compressor runs when the defroster is on, one being it acts as an air dryer, the other is it keeps the compressor from sitting idle through the winter months, prolonging it's life.
-but-
I've had many vehicles with no AC (My YJ for instance) and it is not needed to clear a windshield. It's nice and works quicker, but not needed.

Honestly if this 5-10 second cycling thing is uncurable, I will definately install an override switch. It will also open up a few options for heating vent configurations in the winter without having to run the compressor.

It may seem drastic, but it's bugging the heck out of me. If I am easing to a stop at a light for instance, the compressor will cycle and the Jeep will want to lunge forward slightly. It's ridiculous :x

 

[jay79cj7]

I understand your being annoyed. I was the same way for a while after I first noticed it. I think I have just got used to it now. I agree, if that's the way its supposed to work, it does seem stupid. If you find a way to fix it without an override switch, please let me know.

 

[White]

The York works a lot better at a higher idle.

8)

 

[MudderChuck]

Hands Free Headset...

10 to 15 second cycles seems way to short. Depending on the model year, there are only a few things that shut the compressor down or cycle it. The thermostat, has a built in tempurature differential, a minimum where it shuts down and a maximum where it starts back up again, the two tempuratures (or the differential) are engineered far enough apart, to avoid short cycling.
The low pressure switch, shuts down the system when the theoretical low pressure values, can ice up the condensor. Low freon can cause it to short cycle. As can a sticky expansion valve (rare).
Some systems have a high pressure switch, to keep the compressor from building so much pressure, something breaks. Air in the system (mixed in with the freon) can trigger this, as well as a plugged expansion valve. A little moisture mixed in with the freon can cause an ice block inside the expansion valve, but when this happens the valve usually sticks open, iceing up the condensor and often the return line to the compressor.
I´d have somebody check your low pressure, during A/C operation.

 

[TwistedCU]

Had to look for this one!!! Well I just wanted to let those who suggested it was short cycling know they were right. My A/C gradually got warmer so I got it recharged last week and she is cold as can be and not acting up anymore.

 

[mud4feet]

Had to look for this one!!! Well I just wanted to let those who suggested it was short cycling know they were right. My A/C gradually got warmer so I got it recharged last week and she is cold as can be and not acting up anymore.

Is this a great site, or what!?!?!?!

 

[XJNick]

Hi,

Yes but did you fix the leak? A properly sealed A/C system shouldn't be loosing refrigerant.

-Nick :!:

 

[TwistedCU]

Hi,

Yes but did you fix the leak? A properly sealed A/C system shouldn't be loosing refrigerant.

-Nick :!:

No leaks. It was tested. Refridgerant doesn't last forever ya know. From what I understand the newer systems tend to deplete quicker than the old ones.

 

[XJNick]

From what I understand the newer systems tend to deplete quicker than the old ones.

I've never heard of A/C systems' refrigerant "depleting" over time unless there is a leak. True, the refrigerant could become less effective as it ages, but it shouldn't be leaving the system unless there is a leak, as the system is (or is supposed to be) completely sealed. if it was normal to loose refrigerant then everything that uses refrigerant (Home A/Cs, Car A/Cs, Refrigerators, Freezers, etc..) would have to be recharged frequently (which is not the case).

Just my $0.02 but I think you had/have a leak. They are very hard to detect if they are small and/or in hard to see places (such as leaking through the barrier hoses, evaperator coil, etc..)

-Nick :!:

 

[TwistedCU]

I had a toyota that worked over 3 years after recharging. Still worked great when I sold it.

A Pontiac sunbird 1 1/2 years after recharge was blowing cold air when a Chevy 2500 plowed into me.

If I have a leak on the XJ, it wasnt detected when it was serviced. It is possible the evaporator is leaking, but if so I will know soon enough. Hope not, doubt it, but it is possible.

 

[mingez]

I had a toyota that worked over 3 years after recharging. Still worked great when I sold it.

A Pontiac sunbird 1 1/2 years after recharge was blowing cold air when a Chevy 2500 plowed into me.

If I have a leak on the XJ, it wasnt detected when it was serviced. It is possible the evaporator is leaking, but if so I will know soon enough. Hope not, doubt it, but it is possible.

A-C-A-SCHMEE... I can't believe you owned a Sunbird. :lol: