My AC has not been working. I drew a vacuum to -1bar and added most of 1 can of Freon but it would not take the whole can and would not take a second. The compressor clutch does not engage (I am guessing due to low freon, bit on a retrofit system like this I don't know if that is part of the logic). How to I engage the clutch so system will take the charge? Any advise is great.

Thanks!

 

By pass the low pressure switch until it starts taking charge.

 

Usually, I just jumper the low pressure switch on the receiver dryer (mounted behind the head light cross bar, left side) to engage the compressor. Just be careful, you will be working extremely close to the electric cooling fan mounted in front of the condenser.

Did the charging system work properly at one time?

Brian.

 

You didn't vacuum the system low enough.

 

How did you go about filling it? Be specific.

 

Filled correctly, then pressure in the can is ~85psi, and that's enough to kick the system on, and should take a couple cans without much issue..if it had a proper vacuum, as noted.

I don't like filling systems from the little cans myself.

 

1 bar vacuum is 29.53 inches of mercury or 14.50 psi.

 

With the engine cold, not running, and the rest of the car cold, you can charge liquid into the system without starting the engine. Connect the refrigerant can, purge air from the connecting hose, then turn the can so that the valve is at the bottom. Warm the can with your hands. The difference in temperature between the can and the system will cause the pressure to push liquid into the car. Put the correct amount in before you start the car. If you are charging through a charging manifold with gauges and valves, charge liquid through the high-side port (red valve). if you are using a single-hose setup, you'll be charging through the low pressure port, and will need to wait some extra time to make sure all the liquid has flahed to vapor before you start the engine and run the compressor.

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When charging with vapor (can with valve side up) into the low-pressure side of the system with engine running, the suction (relative) from the system pulls the vapor in. Even with the engine and compressor off, the liquid in the can flashes to vapor. Just as it does in the car, this evaporation requires heat to boil the liquid. In the car, the heat comes from cabin air passing through the evaporator coils. When tat evaporation happens in the can, there isn't the same amount of heat available. The can gets cold, to the point where there's no more evaporation, and no pressure difference to cause refrigerant to go from the can into the system. Solution is to warm the can. A system that's operating with a suction-side pressure below say 20 PSI will freeze the can, so heat from your hands may not be enough. It's OK to use a backet of warm (not hot) water to help keep the can from freezing.


When you charge with liquid as I described in the firts section, the evaporation happens outside the can. So the can doesn't get nearly as cold nearly as fast. Theheat from your hands is plenty, at least so long as the temperature in the system (ambient since the car is sittting "cold") is less that 80-85º F.


Be sure to put the correct amount of the corect oil in your evacuated and cleaned system.