Air Conditioning Cycling On/Off Issue

[Wandering Albatross]

The interesting part is that the duty cycle of the compressor seems to change from almost 100% (or so it feels) to 50% depending on the conditions. It is this change that I am having trouble understanding. If it was always 50% then it would be easier to buy into.

[GasSavers_RoadWarrior]

Some vehicles have AC cutoff under acceleration, not just cutting out while you're pulsing is it?

[ThisThingOfOurs]

I had a similar problem on mine. Turned out to be the power cable going to it was cut and sometimes would make contact and sometimes not. The cable color is red.

[R.I.D.E.]

Dumb question but are you using recirculate or fresh air?

regards
gary

[kamesama980]

I'm actually trained in AC and some of you guys are scaring me..


Your problem sounds very much like moisture in the system. it freezes at the pressure/temperature drop point (the expansion valve) and the hi-side pressure maxes out so the compresser shuts off meanwhile you don't get any cooling. after a bit, the ice melts and refrigerant flows again, you cool off and the comrpesser cycles on again till the moisture freezes again.

that means you need to have the refrigerant checked for water content, system leak checked, and if there is moisture, recover the refrigerant, vacuum the system, replace the reciever-dryer or accumulator, and recharge the system.

[Ford Man]

Originally Posted by kamesama980

I'm actually trained in AC and some of you guys are scaring me..


Your problem sounds very much like moisture in the system. it freezes at the pressure/temperature drop point (the expansion valve) and the hi-side pressure maxes out so the compressor shuts off meanwhile you don't get any cooling. after a bit, the ice melts and refrigerant flows again, you cool off and the compressor cycles on again till the moisture freezes again.

that means you need to have the refrigerant checked for water content, system leak checked, and if there is moisture, recover the refrigerant, vacuum the system, replace the receiver-dryer or accumulator, and recharge the system.

I ask if he had checked to see if it was freezing up or not 3 days ago and he never responded. I knew if it were freezing up it would blow warm air until it thawed out, but then he goes on in his next comment to say it was cycling on and off about ever 30 seconds which led me to believe it was something else. I've never saw a system that would freeze and thaw that quickly.

[Wandering Albatross]

Thanks for all the feedback. A couple things:

Yeah, I do use the recurculation button. Regardless once the compressor goes off it still blows hot air.

I will give the system another review to make sure there aren't any lose or damaged wires.

How do I check for freezing? I'm assuming I wait for the system to shut off and then pull over and look at any points that have ice formation on the outside. Where is the expansion valve located in the system? Is it by the dryer? Can a typical AC repair shop check for moisture and if so how is this done?

The system was just pumped down about a month ago to try to solve the cycling issue and then recharged. The behavior did not change and I was told that the freon levels were close to full when they evacuated it. No parts were replaced, just the freon.

There was a point about a week ago when I was climbing a steep hill with the AC on and the system was going crazy with cycling. It was very hot and the cycling on and off go to the point that it almost felt like the engine was missing, but once you turned off the AC it went away. Maybe it was just on the edge of tripping the sensor as a result of freezing.

I appolgize for the delay, got extra busy this week.

I'm doing another drive to the Bay Area this weekend so I'll be checking out these possible problems.

[theholycow]

Originally Posted by Wandering Albatross

There was a point about a week ago when I was climbing a steep hill with the AC on and the system was going crazy with cycling.

I'm sure this isn't the problem and that it has already been said in this thread, but I can't not say it: Some cars turn off the A/C compressor under WOT, or maybe under heavy load conditions.

[Wandering Albatross]

I realize that some cars do this, but I'm having trouble getting specific feedback on when the compressor tends to turn off on a VX.

I'm also having the problem when I'm driving on the freeway at 75mph on level ground in hot weather. It will cycle every couple minutes.

Again, I need someone who has experience with the VX system to let me know if this is typical. That would be a significant help.

[jadziasman]

If you don't even know where the evaporator is on the Civic A/C system, you don't know nearly enough to diagnose it. You need to go to another mechanic to get the A/C repaired since it seems the one you went to didn't know diddly.

If I were in your situation, I would go to a shop that specializes in A/C, not a mechanic who does "everything". Any professional A/C technician doing this for a living will be able to diagnose and repair your A/C system tout de suite.

It's going to cost you but I would rather have an A/C that works when its 100 than sitting in a hot oven any day. My 79 Chevette didn't have A/C and I had to keep the windows rolled up when the mercury passed the century mark. Opening the windows only made it worse when driving at highway speed - it was literally like a convection oven!