A/C Surges RPM's


jasongind

jasongind

15+ Year Member

Joined
Jan 4, 2008
Messages
276
Points
3,101
Age
44
City
Parkland, WA
Vehicle Year
2001
Transmission
Manual
I have an '01 3.0L. When i turn the ac on and the compressor cycles is sharply drops the rpm's by 500 then right back to normal as it cycles off/on. I can even feel it when im at speed on the interstate or just city streets. At idel is the most noticeable. I was wondering if that means I need to charge the system? It blows cold air continously though. Any thoughts? TIZ
 
I had an issue like this about ten years ago in my 92 Ranger 3.0. When my AC cycled on, my RPM's dropped considerably. The problem is, I don't remember exactly what I did to fix it. If I remember right, it had something to do with my electrical system. Though, I don't remember if I just changed out a worn serp belt, or if that was when my coil decided to flame out on me. I'm sorry I couldn't be more use, and I hope I haven't gotten your hopes up too much. I would start at the beginning and go from there: When your compressor starts up, it kills part of your engine power. Check your compressor pulley, make sure it isn't trying to seize up on you, check your belt and make sure it isn't slipping when the compressor kicks on, stuff like that. I am not a mechanic, however. I'm just going by what I remember from my own experience ten years ago. Hope this helps some.
 
There is an idle-up control on the A/C system to compensate for drag on the engine by the compressor, looks like it's not working. On mine there is an A/C cycling switch that sends a signal to PCM that activates the clutch on/off cycle. The PCM also probably controls the idle-up. My FSM does not describe the idle-up circuit in the A/C section so you'll have to do some more research. I suggest this site: http://acsource.net/acforum/ and sign in to the forum, there are some pretty knowledgable people there. This site is also good for A/C parts/tools etc. http://www.acsource.com/index.asp
 
Me too!

I also have this problem with my 98. I've tried to just pull the wires off the compressor but then the RPM's go high and stay there. I hate the surging and don't care if I don't have AC. Is there any way to bypass it by "fooling" the sytem into thinking the pressure is what it should be therefore stopping the surging.:icon_confused:
 
Ironhead76, if you don't care about A/C then why don't you just leave it off to correct idle problem as the idle only drops when A/C kicks in? Or am I not understanding your problem/question?
 
Glad you jumped in, rearanger, because I never would have thought of that. I never even knew that. Thanks for the assist, because as I told him, I am not a mechanic. I'm just a weekend warrior when it comes to wrenching on my truck. Thanks again.
 
Rearanger said:
There is an idle-up control on the A/C system to compensate for drag on the engine by the compressor, looks like it's not working. On mine there is an A/C cycling switch that sends a signal to PCM that activates the clutch on/off cycle. The PCM also probably controls the idle-up. My FSM does not describe the idle-up circuit in the A/C section so you'll have to do some more research. I suggest this site: http://acsource.net/acforum/ and sign in to the forum, there are some pretty knowledgable people there. This site is also good for A/C parts/tools etc. http://www.acsource.com/index.asp
Click to expand...

Do you happen to know where or what this control is and looks like. I have done a search (here and google) and came up empty handed.
 
You could also have a problem with the IAC(idle air control) control. It gets dirty and gummed up after time, and may not be responding to small changes in engine rpm. Try cleaning it and see if it makes any change.:)shady
 
jasongind said:
Do you happen to know where or what this control is and looks like.
Click to expand...

On mine it's a switch on the receiver/dryer/accumulator. You won't see much as it just sends an electrical signal to engage the clutch and idle-up. If the switch wasn't working I doubt the clutch would engage. I'm assuming the PCM controls this but I don't know how exactly it works. Using the A/C forum
I linked to might give you access to more knowledgable people.
 
I found my problem ... well partly, in my 98 when I'm standing at the front of the truck,to the right of the compressor is some AC tubing that has a 2 wire connector coming out of it. I unplugged it and found some corrosion inside there. Good news is my RPMs are now constant, but I haven't cleaned it out yet to see if the AC will come back.
 
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