car A/C compressor/freon question

[redrider90]

My wife calls me from LA visiting her daughter. Her daughter's 2009 Honda Civic puts out warm air when she is at stop lights. Rev the motor and it gets cold. Drive away and down the street and it gets cold. The compressor does not make any funny noises. I say this sounds like classic low freon. So one thing leads to another and she ends up at a repair shop. The mechanic says he checks the freon and it is OK. He claims the compressor is bad. I always thought that When compressor act up that 1. they make noise and 2. they either work or do not work but there is no in between.
Is my wife's daughter getting taken for a ride on this one? BTW this thing has been doing this for months. Again no noise and always cools down when RPMs increase. Even sitting still just rev the motor and it cools.
???????

[Groover]

Sounds more like an auxiliary fan issue. Not sure how that car is setup, but on my old BMW 540i there is a an Aux fan that sits in front of the radiator (maybe back, don't recall) that would simulate motion and always run air through the AC related coils. If that fan malfunctioned, the car would do exactly what that one is doing, except for the revving part.... Could be a Aux fan clutch then maybe. Not sure if this all applies to your car, but some cars work like that. To me, it also sounds like the compressor and charge are fine.

[rocker59]

If it has an aux fan for the A/C, it could well be that...

But, if the compressor is getting tired and not compressing as it used to, that might be indicated by the fact that engine RPM will help the A/C cool down.

[Wayne Orwig]

As mentioned, look at the fan.
When the AC is on, and blowing hot air, make sure there is a radiator (condenser) fan running 100% of the time.

[pat80flh]

First thing to check, as mentioned , make sure engine fan is running with A/C compressor engaged.

Most modern compressors are variable displacement "scroll" compressors, and poor performance at idle is a symptom of a worn compressor.

[Gusable]

Hondas in general are notorious for fan motor issues on both sides when they get high miled

[Bonaventure]

First thing to check, as mentioned , make sure engine fan is running with A/C compressor engaged.

Most modern compressors are variable displacement "scroll" compressors, and poor performance at idle is a symptom of a worn compressor.

This.  Long time on low freon can pre-mature wear the compessor since the refrigerant contains lubricant and low freon = low lubricant.

[Randown]

The symptoms you described does not sound like a typical low refrigerant issue.

Typical low refrigerant symptom: The compressor may stay engaged during idle but trips off via low pressure switch when its RPM (and thus pumping capacity) is increased along with the engine.

Find out...

Do the electric fan(s) run with the compressor at idle?

Does the compressor stay engaged during idle? If not what is switching it off?

If YES & YES is answered it could be weak valves in the compressor.

[Don G]

Maybe a new drive belt is in order, had the exact same circumstances on my GMC truck, a new drive belt corrected the fault.  DonG

[redrider90]

Well I appreciate the comments. My last experience with A/C car units was in the days of R12.  Back then low freon would blow warm and then cold when you brought up the RPMs. That is assuming you had some freon in the car.  I gotta tell this story because it is so drop dead stupid and I am lucky I didn't do myself in. In the 70's nobody recycling R12 and you could by it like oil at the parts store. So I was putting new refrigerant in an Oldsmobile. I had gauges but no vacuum pump. So I rigged my connections to use the engine vacuum to fully pull all the air out of the A/C system. I put new desiccant in the system. Of course I had dumped all the previous R12 straight into the atmosphere not knowing I was contributing to the depletion of the Ozone layer. Anyhow I had the engine running and pulling vacuum for 30/45 minutes. I know you cannot get  27 hg of mercury off a car engine but I figured at 20 hg off the engine and if I got he system hot enough and ran it for a good while I would get all H2O out of it. Besides I was poor. So I hooked up my hoses and shut off valves ran it through the manifold on the gauges. Shut it off and let it sit to see if it held vacuum which it did.
I came back out and restarted the engine to pull for another few minutes while I hooked up my freon. I accidentally turned on the freon while the engine was running. Which means I dumped freon into an internal combustion engine which in turn produce a highly toxic poisonous gas that was used in WWI called phosgene. All of a sudden I felt instant burning when I inhaled.  😱  I shut the freon off and ran from the car as fast as I could. I was lucky as I only took one or two breaths of the stuff which was coming out of the exhaust. But even then it was quite potent. So I went back and shut off my valve that was attached to my vacuum on the engine and proceeded to fill the A/C system. I had no trouble with it making cold air at all so my rigged vacuum system did evacuate the A/C system. I didn't know at the time what I had done. But I had a friend who tell that burning freon produces a very lethal gas.  PS: no Darwin award for me!

[Randown]

Good story, illustrative of how ingenuity & DIY can really go awry. Looking back using information readily available to us now thanks to the glorious inter-webs  , assuming you got 20" HG vacuum with your engine that would correspond to an ambient temperature of around 160F for moisture to evaporate, which may have happened. Absent a vacuum pump you could have also purged the system with some refrigerant vapor. The new(ish) HFC refrigerants don't have the phosgene problem, though they have plenty of other problems.