Automotive Air Conditioning Information Forum

Originally tested pressures on Low side at 70 and hi side at 225 probably should have changed low side switch but recovered R-134A and vacuum pumped and tested for leaks. Vacuumed for over an hour. System calls for 60 oz. R-134A So installed 58oz R-134A. Probably lost a couple oz. left in the high side manifold hose. At first the low side was coming up to 70 and 80 and would drop back down to 20 or 30 as the high side was building, but I knew that was to high on the low side, but I kept going so as I installed more R-143A the low side started coming down as the high side went higher. Ultimately when I had installed all the 58 oz of R-134A My low side was still at approximately 57 and my high side was at 275 and with that my air at vent was only in the low 70 with an outside temp at 90 degrees. I'm guessing there's a problem with my low side switch. Any help or other ideas are welcome! Thank You in advance for any ideas!

Which engine in this E350?

How long have you owned it? How many miles on it?

Any history on previous A/C system repairs?

There are several things that can cause performance like you are seeing. The compressor seems healthy with head pressures like that.


Why do you think there is something wrong with the low side switch?

Thank you for your response. I am a novice so I was trying to figure it out. I’ve come to the conclusion that I was wrong about the pressure switch. Ok info on van
The engine is a 5.4 liter. I purchased it in 2005 with just under 10,000 miles Its now got 193,000 on it. It’s never had any A/C work done to it.

The first place I would look is the fan clutch. Even when a clutch is worn out the engine may not overheat.

You can check for airflow issues by spraying the condenser with water & watching the pressures.

I have also seen condensers full of insects & dirt that no longer transfer heat effectively.

If those pressures are at idle, how does the A/C cool at 40+ mph?

Thank you again for the input. The clutch I believe is good. At 40 mph it’s still not cooling. I had the same thought about the evaporator so I looked at it and it is very dirty so I am going to clean it next to see if that works. Any recommendations on cleaning?

Cleaning a filthy condenser is best done with it completely cold. If the grille is not too hard to remove, do so.

I like to use floor stripper & a spray bottle from Home Depot or Lowes - but the stuff is hard on paint & you have to be careful. Simple Green straight out of the bottle works good too. A strong surfactant is what you want.

Spray the fins as deep as you can with cleaner. Soak it good, and let it sit for a few minutes. Then flush it with a garden hose. Do NOT use a high pressure washer, you can bend the fins with too much water pressure. After you rinse it, soak it with cleaner again, let it sit & rinse again.

Thank you