2000 Stang Surging with A/C or defrost on

[rickdupont]

Can anyone help??? My 2000 Mustang has been surging at idle with the a/c or defroster on only while i am driving it is ok. What I meen by surging is with my foot on the break and stoped at a light the car jumps forward. Its like the idle is not being controled. It dosent do it all the time and it only does it while I am in drive if I put it in park it will stop. I checked the A/C unit, the charge is good, and it does not stop and start when this happens. Any sugestions? I am having another problem that might be related this problem has gotten progressively worse. Now I noticed that when the transmission goes to shift especially into higher gears it takes a longer time. almost like if there was no line on the vacuum modulator if there was one. now this problem just started when the surging got really bad . Any help would be apreciated...

 

[00GTpony]

you sure its full of r134

 

[the98stang]

It is most likely the AC cycle switch (unless it won't blow cold air, then have a leak somewhere in the A/C system). Mine was doing the exact same thing.

Take a paper clip and short the switch by connecting the 2 prongs with the paper clip. If your A/C clutch stops cycling on and off (which is why your idle fluctuates), then your switch is bad. But ONLY do that for a few seconds or you fry the switch and mess up many other things. The switch is on the passenger side way in the back corner, near the firewall.

 

[rron91]

The A/C is Ice Cold and the compressor never shuts off when this happens I think the A/C is putting to much load on the motor and the computer is over compensating. The rpms will drop to about 600 then jump to 1200 then back to 600 then 1200 and keep going but only in gear.

 

[the98stang]

The A/C is Ice Cold and the compressor never shuts off when this happens I think the A/C is putting to much load on the motor and the computer is over compensating. The rpms will drop to about 600 then jump to 1200 then back to 600 then 1200 and keep going but only in gear.

Test the cycle switch like I said. 90% sure it's the switch.

 

[RedBullitt]

actually mine was doing the same thing, never figured it out. got sick of screwing with it and i just pulled the ac...

 

[cjb7804]

Posted this in the other thread like this. Just replaced my cycling switched today. Looks like it took care of my problem just like the original posters problem. Part only runs $10 or so. Give it a try.

 

[Mike97gt]

Posted this in the other thread like this. Just replaced my cycling switched today. Looks like it took care of my problem just like the original posters problem. Part only runs $10 or so. Give it a try.

Two most likely causes of this problem are

1. bad cycling switch ( much cheaper to fix)

2. bad CCRM ( more expensive)

Looks like you lucked out and the cheaper item fixed it

Now if the compressor was short cycling ( surge happens when the compressor kicks off) then the R134 charge is most likely low.

 

[cjb7804]

Ya I know. I've been working on this problem for a while now. Originally thought it was a vaccuum problem, but did a bunch of tracing on the schematics and my A/C service manuals and figured it was a good start. Looks like I was a lucky one.