AC Clutch in 2000 Dodge Neon Only Kicks In When Brake Pressed


#1

Recently, noticed that my ac in my 2000 neon was “sluggish.” It seemed to cut out whenever I accelerated, but when slowing down or stopped at stoplights, it surged again. I decided to charge it up with R-134a, as recommended, but discovered while trying to get the first can to take that the AC clutch only kicks in whenever the brake is pressed in. Does anyone have any idea why this is happening? Thanks!


#2

ill bet you put the can in with the engine ruuning,on the high side,and you were fine.??? with the a-c on and compressor running too.


#3

If that clutch only kicks in with the brake depressed it certainly sounds like a vacuum problem. I would start by checking all the vacuum lines for loose connections or damaged hoses.


#4

The coupler on the fill kit will only fit on the low side fill valve.

It sounds like the system may be overcharged, not undercharged, or there is a restriction in the orifice tube/expansion valve (not sure which your car has). When the compressor speeds up as you accelerate, the system becomes too highly pressurized, and the high-limit switch (or equivalent) shuts off the compressor.


#5

It seemed to cut out whenever I accelerated,

Uh, it’s supposed to do that. AC compressors are disengaged when more power is called for during acceleration.

the AC clutch only kicks in whenever the brake is pressed in.

That’s an odd one. As suggested above, it could be something to do with vacuum. Perhaps the switch that cuts out the compressor works on reading manifold vacuum, and either the switch is bad or something is wrong such that braking just “puts it over the limit” (a power brake unit is powered by engine vacuum).


#6

I like that. I could not figure out exactly what the connection would be as I would expect the vacuum to drop when the brakes were used, but that cut out switch would be just the thing. If the switch is over sensitive or the vacuum is generally low for some reason (leaks?) that would explain it and it would also tend to cause the A/C to shut down under more mild acieration than designed for.


#7

bobby,
If you ever come back, we may be able to help you IF you use words in a way which most people have an understanding of; such as: “sluggish”; cut out; surged; to take; kicks in. Give a difinition of each of these words; or, use words in a more common way.
Then, we may be able to help you. Until then, not able.


#8

There is a vacuum supply line for the A/C system that comes off the check valve on the booster. The vacuum controls only the recirculation door, nothing else. I’ve checked the wiring diagram and there doesn’t seem to be any common electrical connection between the A/C system and the brakes.

It’s possible it is just a coincedence that the compressor kicks in when the brakes are applied. It’s an interesting problem and I will continue to look into it, I’ll post back again if I find anything.

UPDATE… The common component is the PCM. It controlls the ground side of the compressor relay and gets an input from the brake switch. If this is truely whats happening, then for some reason the PCM is grounding the compressor relay when it sees the brake light input. It could be a defective PCM but that’s just a guess.


#9

Thanks everyone for your input. It’s been very nice having so many ideas thrown my way! I’m figuring it’s probably something with the vacuum system, like the cut-out valve. As far as I can tell, the AC clutch ONLY comes on when the brake is pressed, not at any other time. This is not the way the car was designed because it only started doing it this weekend. Thus, that leads me to conclude that something has made the system go crazy. This also leads me to conclude that the system isn’t OVERCHARGED since it was doing it BEFORE I tried restocking it with R-134a. Yep, best bet looks like a vacuum line issue. I’ll keep everyone posted when I find anything out. Thanks again for all of your input!