A/C Short Cycling - Low/Rough Idle

[BrandonVA]

Hello,

I tried posting this on a ford escape forum but everyone over there seems to think every problem can be fixed by cleaning/replacing the iac and throttle body...

anyways, when I have my a/c turned on the compressor seems to cycle on and off quite rapidly causing fluctuations in idle. I think it is cycling too fast for the iac to adjust the idle properly. Every 5-10 seconds there is a loud clicking noise which I believe is the compressor engaging.

It blows very cold air so I don't think it is low on freon. I tried jumping the refrigerant pressure switch and the idle is a lot more constant. before, the idle would sometimes drop to 200-300 rpm and the vibration would be extremely bad. I know something isn't right but can't quite figure out what.

any ideas before I waste more money?

 

[Donald]

You are guessing until you connect up a set of manifold gauges and see what is really going on. Don't add R134A until you have determined the pressure.

As for cold air coming out, you need a probe thermometer (cheap) stuck into the vent to check, and then determine if its proper based upon ambient temp outside.

 

[zzyzzx]

I also suspect that you are low on r134a.

 

[brandini]

I have a mazda 3 which is very similar to the escape and my ac would do that when overfilled by the horrid place I purchased it from. On hot days it would cycle oddly.

Gauges to check pressure, not the gauge on a bottle.

 

[Donald]

Originally Posted By: zzyzzx
I also suspect that you are low on r134a.


I agree, but he should not guess. Hook up gauges or bring it to someone.

 

[JHZR2]

Originally Posted By: Donald
Originally Posted By: zzyzzx
I also suspect that you are low on r134a.


I agree, but he should not guess. Hook up gauges or bring it to someone.


Agree on both counts. Low pressure can make things very cold... So long as pressures high enough to allow the compressor to engage, it will until it trips for something else.

 

[bullwinkle]

What's the outside ambient temperature? Might be cool enough that the low side switch is cutting off the compressor. Might be able to block off the condenser (TEMPORARILY) for a couple of minutes if it's cool out to raise pressures & see if the compressor stays running. Or it could be low on refrigerant!

 

[SrDriver]

If it needs refrigerant make sure you purge the low side hose of air before adding any.

Best to take it to a shop that has the proper tools and if low indicates a leak somewhere in the system.

 

[JamesBond]

Originally Posted By: BrandonVA
Hello,

I tried posting this on a ford escape forum but everyone over there seems to think every problem can be fixed by cleaning/replacing the iac and throttle body...


So did you try cleaning the icv and tb?

 

[BrandonVA]

Originally Posted By: JamesBond
Originally Posted By: BrandonVA
Hello,

I tried posting this on a ford escape forum but everyone over there seems to think every problem can be fixed by cleaning/replacing the iac and throttle body...


So did you try cleaning the icv and tb?



omg....

YES!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

[artificialist]

Did you get your car new, or used? Sometimes people will use a refrigerant fill kit, and that charge isn't perfect. What is worse about those kits is that sometimes they have additives that aren't OEM approved.

How well do your cooling fans work? They should quickly speed up after the A/C is switched on. If they don't function properly, high side pressure rises so far that the compressor is switched off. Excessive refrigerant makes the problem worse, and that often happens when those DIY fill kits are used.

 

[ARB1977]

I just filled my Tacoma with R134A. Very easy to do. Bought the straight stuff..about the same price but you get half as much.

 

[artificialist]

Originally Posted By: ARB1977
I just filled my Tacoma with R134A. Very easy to do. Bought the straight stuff..about the same price but you get half as much.

I know you can get really close to perfect with DIY kits, if you know exactly what you are doing. I have done this to a few cars in my family. Back when R-12 was standard, my dad DIY filled several cars in our family with success

Problem is not everybody does.

 

[01rangerxl]

Fords tend to engage/disengage the compressor frequently, especially at idle. My truck has done it since new, but nowhere near every 5-10 seconds. That does seem excessive and would likely indicate a low charge.

You need to hook it up to some manifold gauges and get a low and high side reading. The gauges on DIY kits are often very inaccurate.

My truck is just a touch low on freon (checked recently with manifold gauge on high and low ports), and it doesn't cycle the compressor nearly that often. My A/C is super cold, colder than the trucks at work with 110-120K fewer miles on them.