Hi all,

I have a 99 civic DX and the AC keeps turning on and off when idle.
I brought it to "Ice Cold Air" and they said the high presser side was really high (over 300psi) at idle and i probably have a clog somewhere. They suggested replacing the condenser and the reciever/dryer for $400.

Last summer (July 2010) i changed the condenser, accumulator and condensor fan myself so i really doubt there is a clog in it since it's pretty much brand new. When i filled up the system, i think i only pulled like -15psi vacum.

The year before that (Aug 2009) i had a mechanic replace the Compressor cause it sounded like it was falling apart.

What do you guys think it could be?

 

What was the low side pressure? Did you possibly overcharge the system with refrigerant?

 

I only put 1 can of refrigerant in, i think it was only 18oz. It had a small gauge on it and it was in the green zone when i was done.

 

That cheap gauge is basically worthless. You need a manifold gauge set to measure pressures on BOTH the high and low sides. Both readings are needed to diagnose the problem.

 

I just took the reading this moring. The AC keeps turning on and off every 20 seconds. The high side hits around 205 psi then turns the compressor off, when the compressor is off the low side starts to rise and when the low side gets up to 47 the compressor kicks back on. When the compressor kicks back on the low side drops to 20 psi, and the high side drops to 175. The high side gradually rises to 205 and the cycle repeats.

 

Give more details about this work. Before adding refrigerant to an A/C system empty of refrigerant, you must COMPLETELY evacuate the system (pull a full vacuum = ~0 PSI; no vacuum = ~14.7 PSI), disconnect the vacuum pump, and then watch to see whether the system holds vacuum overnight to verify that there are no leaks. If so, then the system is recharged with the proper amount of refrigerant. Is this what you did?

The rate at which the compressor cycles on and off depends on the outside temperature and the speed setting of the cabin blower. How did you do the test?

You generally want to have the A/C running for 10 minutes before making the pressure measurements. Then open all the car doors and turn the A/C on and the blower to MAX. Doing the test this way, there should be little or no variation in the high and low side pressure readings over time, contrary to what you are seeing.

Here are pressure readings I took 2 years ago from my 2000 Civic (A/C working fine):

Try doing your test similar to what I did and compare the readings.

 

I thought you were supposed to get -30psi for the vacuum before adding the freon. I was pulling around -11psi vacuum, i got impatient and only waited 30 mins before adding the freon. It didn't seem like the vacuum changed over those 30 mins.



So is it normal for the compressor to cycle on and off? I thought it was supposed to always be on if the A/C was running, and it would turn off if there was a problem (low freon, high pressure too high).


I will let the AC run for 10 mins and take new measurements tonight.

 

Are you mixing up "PSI" and "inches of mercury" pressure readings? Click here.

It is normal for the A/C compressor and fan to turn on and off. This is controlled by the A/C thermostat in the evaporator. What's not normal are your widely variable pressure readings with the A/C on.

Does your A/C have any cooling problems?

 

Following the guide in this thread, they say the vacuum should be -29.92 psi before adding the freon.

It starts to get cool and then it switches off. Fan blows fine.

 

The thread has some errors (minor). You missed the correction quote below in the first post of the thread:

Also note in the link that I posted that 100% vacuum is never a negative pressure value.

So the A/C never gets cold, right? Are you saying that the condenser fan runs when the A/C is on or that the cabin blower blows fine?

 

I meant the cabin blower blows fine, but so does the condenser fan when the AC is on.

The AC gets cool, but then shuts off and starts to blow warm air. It's most noticeable when stopped in traffic. I can hear the AC clicking off then it starts blowing warm air, and i start sweating.

 

Make the new refrigerant pressure readings under conditions mentioned above. Afterward, also try spraying the condenser with water from a garden hose to see whether this makes the A/C blow cold continuously. Also post the pressure readings when the latter test is done.

 

The new measurements i got were

high - low
250 - 50

After i sprayed the condenser with the hose it droppped to
210 - 25

When it started turning on and off, it would stay on for like 5 mins, the turn off for 5 seconds and then turn back on and repeat the cycle.

When the compressor turned off the high dropped to around 200 while the low started to rise, once the low side hits 50 (after 5 seconds), it kicks back on.

 

What was the outside temperature during the new test?

Was the A/C blowing cold at this moment?

Did this make the A/C blow even colder?

I suspect the A/C blows warm air when this happens. Does spraying the condenser with water stop the rapid cycling and make the A/C blow cold?

When the A/C was turned off, do the high and low side pressures rapidly or slowly equalize?

 

^ You are genius!

 

~76 degrees F

Yes, it blows cool when the compressor is running.

It felt a little cooler

I didn't try this because the water was hitting the condenser fan and spraying everywhere. And also it took a while for it to start clicking on and off. It was running for a good 10 minutes before it started clicking on and off. But this morning it was doing it right after i started the car.
Should i try this next time?

pretty Slow, around a 1 or 2 minutes, they equalized at around 115.

 

Based on your new information, I believe your A/C system may be overcharged with refrigerant.

 

Do you think i should do a complete evac and recharge?

 

I believe so, but let me explain. Your high side (discharge) pressure looks fine, but your low side (suction) looks too high. Here's what the service manual says:



So I guess the expansion valve and capillary tubes are also possible, but you could possibly rule them out by feeling the low pressure hose and check joint.

 

Thanks, i guess i will try the evac recharge first and see if that fixes the problem, as it the easiest and cheapest route. If not i guess i will replace the expansion valve. What sucks is all the places down here charge around $40 just to discharge your system.

If i end up changing the Expansion valve, should i go ahead and change the evaporator too?

 

Does the price of recovery also include subsequent evacuation of the system? If so, you can just recharge the system yourself. The amount of refrigerant to add to your empty evacuated system is 21.1 -22.9 oz of R134a. The thread you mentioned earlier details how this is done properly.

 

I finally got around to doing this.

When i hook up the vacuum to my car, it goes to -30 psi, but as soon as i close both valves it drops to zero over the next 5-10 seconds. Does this mean i have a bad leak? If so what is the best way to find the leak, the UV fluid and light or an electronic leak detector?

Before i got it drained, i noticed there was alot of foam and bubbles inside the accumulator.

Thanks.

 

This doesn't make sense because you did not have a leak prior to recovery of the refrigerant.

Take pictures of how you are pulling vacuum on the system and what valves you are closing when the system apparently loses vacuum.

 

I'll have to take a picture after work, But i'm closing the red & blue valves that are attached to the gauges (right under the gauges) while the vacuum is still running. Once they are closed i lose the vacuum and it goes down to zero after around 5 seconds.

I think i had the same issue after i originally changed the condensor/accumulator last july, but i just filled it up with freon anyways. Seems like a pretty big leak though if it goes down to zero in 5 seconds.

 

This is what just doesn't make sense. Your system was holding refrigerant prior to draining, right? Post clear pictures of your pump/gauge set up connected to the A/C system.