Automotive Air Conditioning Information Forum

Greetings. About 6 years ago this forum helped my convert a 1994 Toyota pickup V6 automatic from R12 to 134A. All parts, everything in the Toyota were replaced except the copper lines and the amplifier. The system worked so so and the only issue I had was the evaporator would freeze up at highway speeds on hot days. A bit of an inconvenience, but I learned to live with it.

Last year on a trip, this is an RV. The evaporator was freezing up often, I stopped to get it fixed and the tech told me there was a blockage and the evaporator and the condenser needed to be replaced as they did not know which was plugged. I declined and continued on my trip. I took my RV to my local guy, good people but general mechanics not high end AC techs. Kirk told me the pressures was very high 400 psi and that there was a blockage, but he was not sure where and told me I would be better off taking it to an AC specialty shop.

The AC stopped working, so off to the specialty shop and was told very high pressures and AC fuse blown, likely due to high pressures, also low on 134 but no leaks found. They have had it 2 days, tech is thinking the engine fan is not pulling enough air across condenser and is suggesting an electric fan. I told them that the system has worked and has been evacuated once to replace a leaking pressure valve and another time to reposition the thermister as suggested on this forum. So at least twice over the years the system worked properly, I think I had the 134 checked another time also before a trip, not 100% sure on that.

Any ideas, thoughts, opinions, suggestions greatly appreciated.

Keep using the mechanic who said you don't have enough condenser airflow. A blockage almost always kills performance, but you say it can freeze up the evaporator. I think your mechanic is probably correct, need better condenser airflow

Thanks for the response, appreciated. Not arguing but it does seem that I cannot get more airflow than traveling 70 mph on the highway?? Which is when the evaporator freezes up.

Shop told me today they suspect the fan clutch is the issue and have ordered a new one. Which would cause low air flow across the condenser. It is an Aisin fan clutch and less than 2 years old with couple thousand miles on it. I have mixed feelings about them suggesting an electric fan and not noticing the fan clutch was not up to snuff. They are suppose to be a top shop and have a good reputation.

jjrbus wrote: ↑Fri Apr 22, 2022 6:52 am Thanks for the response, appreciated. Not arguing but it does seem that I cannot get more airflow than traveling 70 mph on the highway?? Which is when the evaporator freezes up.
Shop told me today they suspect the fan clutch is the issue and have ordered a new one. Which would cause low air flow across the condenser. It is an Aisin fan clutch and less than 2 years old with couple thousand miles on it. I have mixed feelings about them suggesting an electric fan and not noticing the fan clutch was not up to snuff. They are suppose to be a top shop and have a good reputation.

Viscous fan clutches can and do give out, and it's wise to replace them every few years.

With that kind of pressure on the high side, it could also be a blockage, either in a line, in the receiver/dryer (presuming it has one), or in the condenser itself. Or, it could also be an overcharge. Was the system recently re-charged just prior to the high-pressure condition and failure to cool? Is the compressor noisy?

If you do any work on this yourself, be sure to protect your eyes in case a hose should burst.

Shop called this morning. They replaced the fan clutch and say they cannot force the AC to freeze up! $300.11 total. The first shop in Alabama that looked at this diagnosed blockage but could not pin point blockage and wanted to replace everything, over $1000. My mechanic said take it to an AC shop. There are 2 people with wrench's that did not diagnose the clutch issue. What really upsets me I am a fully You Tube certified mechanic and I did not think the clutch was bad! Guess I will never get that coveted Shade Tree Mechanic certification's!

Thanks for the input always great to have someone to bounce issues off.

JohnHere wrote: ↑Sat Apr 23, 2022 9:55 am Viscous fan clutches can and do give out, and it's wise to replace them every few years.

I have observed the same here in Arizona. I use Hayden on my 1988 Mazda (replaced free several times in 27 years with my 1988 Mazda truck) and O'Reilly on my 1998 Frontier with 260K (replaced factory unit, but replacement one has lifetime warranty).

I was so happy, $300 and I have meat locker, maybe I should start wearing long johns when I drive? Get in RV and no AC. Oh well back to the shop..

jjrbus wrote: ↑Sat Apr 30, 2022 3:21 am I was so happy, $300 and I have meat locker, maybe I should start wearing long johns when I drive? Get in RV and no AC. Oh well back to the shop..

Not sure I understand. It was fixed and now it's not fixed?

Yep, was working great when I left the shop. Now it is blowing hot air. Back to the shop.

Have you put gauges on it to see whether the system is still pressurized? Static pressures will do for now. They should be roughly equal to the ambient temperature. If not, then it has a leak someplace.