95 escort erattic idle when ac or heaters turned on

[Brad Weirr]

Hi .....i have a 95 escort /seems to run good.......but when i turn on the ac or heater controls.....it seems to idle weird.....kicks in to high idle ..then low and just repeats itself.......this effect is noticed when standing still or driving at highway speeds......would appreciate help on it.......thanx

[denisond3]

The a.c. system comes on when you have the heater in the 'defrost' position, even if you have the a.c. button OFF; but not when the heater is not set for 'defrost'. At least that is the way it is supposed to work. And the idle is normally increased whenever the a.c. is on (or the defroster), but not for just the normal heating. The change in idle speed is supposed to be controlled by the idle air control valve, responding to the PCM telling it what to do. A sticking or clogged idle air control valve (IACV) could be one culprit. My viewpoint is that the IACV is going to misbehave eventually on any car - though it may happen at 80k miles or 280k miles.
Also, if the a.c. system is low on fluid and you turn on the a.c., the compressor will not stay on continuously, but will cycle on--off, on--off. This is more likely in cool weather too. When it is cycling on and off, it may result in the engine speed surging while the PCM is trying to keep up with the correct idle speed. A system that has lost any more than about half of its freon will likely cycle on for 2 to 10 seconds, then cycle off for a similar length of time.
Could this be what is happening? The quickest/simplest way to tell if your a.c. system is working okay, is to run the a.c. and have the hood open. The high pressure side hose coming up from the compressor (near the air-filter housing) will be toasty warm, the low side pressure going into the compressor (bigger diameter, running down past the alternator) will be very noticeably cooler.

[Brad Weirr]

Originally Posted by Brad Weirr

Hi .....i have a 95 escort /seems to run good.......but when i turn on the ac or heater controls.....it seems to idle weird.....kicks in to high idle ..then low and just repeats itself.......this effect is noticed when standing still or driving at highway speeds......would appreciate help on it.......thanx

Thanx Denisond3.......
Sorry ....I meant the ac comes on when in switch normal operating positions.....which is normal....the engine cyles with idles as you mentioned every 2 to 10 seconds.....high/then low....

But when i use the normal operating positions for the heater controls...the heat comes on and not the a.c. with is normal.....but the engine still cylces with idles as you mentioned every 2 to 10 seconds...high/then low

a erratic idling cyle that i have never witnessed with any other vehicles with or without a/c.....

I can understand it reacting this way in the a.c. mode.....if freeon levels r inadequate as you state,.but cant understand why it would do this in normal heater use conditions... I've checked the hoses as you mentioned and all is normal.....as well I didn't think it was a low level freon condition due to excellent cooling in the cab of the car when in extreme out door hot temperatures....

[mightymoose_22]

If I understand correctly, you are saying that after turning the a/c OFF, the engine still behaves as if it is on?

With the a/c and heater off, how does the engine act if you start it up and let it idle?

If normal, how does it act if you then turn on the heater with the selector on PANEL?

If still normal, how does it act if you then switch on the a/c and move the control to RECIRC?

When the fan is blowing, move the selector between PANEL and FLOOR and see if you can feel the air diverting. Feel at the top of the dash and see if anything is coming out up there.

It sounds like one of two things to me... somehow your a/c switch is stuck in the ON position (button broken), or the defroster is stuck on.

One last thing... if you have the switch for the rear defroster, I believe that will also effect the engine idle. Make sure that it isn't on if you have it.

Tell us the symptoms with the above conditions and we can see if it points to anything specific.