auto a/c question

[deerefan]

My mother in law has a 2005 honda element and was driving home today from work and the a/c did something weird. It was blowing cold and she turned it up a bit b/c it was too cold. After a while she noticed the air was getting warmer. It had not gotten any better by the time she got home. When I hooked the gauge to the low side, it pegged out and would not take freon. The compressor would not kick on. Do auto a/c compressors go into thermal overload if they are low on freon? I am going back in the morning to try again, see if it cools off. Thoughts?

 

[Stihlrunner]

Most likely there is a blockage in the system, most likely an orifice or valve.

Most R134a systems are charged through the high side.

You risk overcharging the system, essentially causing a hydro-lock and damaging very expensive components. I would pull the fuse for the compressor and take it to an AC shop to have the system evacuated and recharged to specification.

 

[dstig1]

My mother in law has a 2005 honda element and was driving home today from work and the a/c did something weird. It was blowing cold and she turned it up a bit b/c it was too cold. After a while she noticed the air was getting warmer. It had not gotten any better by the time she got home. When I hooked the gauge to the low side, it pegged out and would not take freon. The compressor would not kick on. Do auto a/c compressors go into thermal overload if they are low on freon? I am going back in the morning to try again, see if it cools off. Thoughts?

There is no real thermal overload, just high and low pressure cutout switches.

If it is low on freon, the pressures should have shown that - very low. What were the readings - high side and low side? Ambient temp? It may have tripped the high pressure cutout switch, which would be why the compressor wouldn't cycle.

It is possible if you run the AC on MAX or Recirc and set the fan low that the condensor can ice up from low airflow over it. That would kill the cool air, but I wouldn't expect the pressure to spike.

It's possible something broke loose in the system and is plugging up the works. Need more info to go on. Check fuses, jumper pressure switches (only for a couple seconds!!) to verify, and make sure the electrical side is working too.

Look for a huge puddle of water under the car if it iced up.

Get some more info in the AM and report back when it cools down. Myself or others here can likely help out. There are also AC forums on the web with lots of great expertise.

Good luck!

Dave

 

[hosspuller]

Most R134a systems are charged through the high side.

High side ???? Careful there ...

 

[dstig1]

I charge an empty, evacuated system with liquid on the high side - until it stops taking it (engine off). Then I use vapor on the low side, and then turn on the car and AC to draw enough in to get it up to spec. But I have a limited stable of vehicles I do AC work on, and this may not work for all systems...

And the common AC system DIY problem: Never start by adding refrigerant. You need high/low side gages to see what is going on first. Then research the cause before attacking it.

 

[deerefan]

There is no real thermal overload, just high and low pressure cutout switches.

If it is low on freon, the pressures should have shown that - very low. What were the readings - high side and low side? Ambient temp? It may have tripped the high pressure cutout switch, which would be why the compressor wouldn't cycle.

It is possible if you run the AC on MAX or Recirc and set the fan low that the condensor can ice up from low airflow over it. That would kill the cool air, but I wouldn't expect the pressure to spike.

It's possible something broke loose in the system and is plugging up the works. Need more info to go on. Check fuses, jumper pressure switches (only for a couple seconds!!) to verify, and make sure the electrical side is working too.

Look for a huge puddle of water under the car if it iced up.

Get some more info in the AM and report back when it cools down. Myself or others here can likely help out. There are also AC forums on the web with lots of great expertise.

Good luck!

Dave

Will do. I consider myself a shadetree mechanic (minor repairs and maintenance, especially newer vehicles) so if is something major I do not have the right tools to fix it, therefore off to the mechanic it will go. I will report back tomorrow morning.

 

[chad22]

High side ???? Careful there ...

Yes ac should be charged on the low side. If the ac is low on refrigerant. There's usually a pressure switch which keeps the ac compressor from kicking in to prevent damage to it.

What was the reading on the low side? Should at least be 35 PSI. There's always a chance that either your low or high side valve has worn out and isn't sealing and causing the refrigerant to leak out.

That would explain the ac blowing warm air.

I do MVAC work every now and then. Whenever I fix an ac before any refrigerant is added to the system. I always replace both those valves and the customers are told that before hand. Heck it's only $10.00 extra on the bill for those valves.

Cheaper than having the system leak down again and refilling once again.

Also once you open up the system to the environment you need a vacuum pulled on it to remove any contaminates.

This info is coming from a 609 certified MVAC Technician.

Certification number :94851CB76ADAB9020

Certification number was listed to show that I am really certified.

Chad

 

[deerefan]

It started working this am on her way to work. I told her to use it sparingly on the way home and i will check the freon again. This leads me to believe it was low and kicked out, but i can't be 100%

 

[dstig1]

I don't agree with that diagnosis, based on the info provided. If it was low, it would not be working now as it would still be low. My money is on an iced-up evap, until you have any further info/readings to show otherwise. The symptoms you described fit that as a cause, including the fact that it is now working fine. Tell her to not run it on Max/Recirc with the fan set real low, and that may solve the problem.

It is also possible that the Low pressure switch is bad or out of adjustment and letting the evap get too cold, leading to ice-up. They are cheap and easy to change without having to vent the entire system as there is a valve in front of them to keep the freon in.

 

[deerefan]

I don't agree with that diagnosis, based on the info provided. If it was low, it would not be working now as it would still be low. My money is on an iced-up evap, until you have any further info/readings to show otherwise. The symptoms you described fit that as a cause, including the fact that it is now working fine. Tell her to not run it on Max/Recirc with the fan set real low, and that may solve the problem.

It is also possible that the Low pressure switch is bad or out of adjustment and letting the evap get too cold, leading to ice-up. They are cheap and easy to change without having to vent the entire system as there is a valve in front of them to keep the freon in.

I am not too saavy on a/c work, my diagnosis was a guess at best. If the evap ices up, the air will blow warm or not at all?