Can someone tell me how many oz. of refrigerant it takes to charge the A/C in a '90 F150?

The old truck lives at the lake and is only used on weekends, but I've gradually been fixing all the little things that are wrong with it and it's turned out to be a pretty solid truck. It has 120K miles and a rebuilt trans, and I only paid $750 for it. I decided to see if I could resurrect the A/C, and got it to where the compressor will at least engage. I've put 36 oz of refrigerant in, but it still short cycles, and it doesn't blow cold air. There doesn't seem to be any leaks, and everything else appears to work properly.

 

that should be plenty....

vac it all out and change the screen....it may be plugged...check high/low gauge readings to see...

sometimes the dryer will not be as effective...

ALSO..DONT put in ANY freon with OIL in it...you never lose the oil when the freon leaks out and adding more just makes it cool less...

here is how I add freon...

1) test to make sure it is operational...
2) start vehicle and warm up to normal with the AC set at MAX and fan on High...
3)Put a temp gauge in the vent to check temperature...
3)hook freon to low side port on dryer...
4) set idle at 2,500rpms (normal driving rpm range)
5) open freon and fill if needed if compressor is still cycling...I fill just until the cycling stops at the set rpm range...

This always netted me the coldest temps...currently my f150 blows 31deg out the vents on max with fan on high...not bad for 95deg weather...

 

OOPS. Too late on the oil thing. But, of the three 12oz. cans I added, only one had an oil addititive. I figured that since it hadn't been run for a few years it could use a little lubrication.

Where is the screen you mentioned?

Thanks for the advice.

 

31 degrees?! That's insane! I'm jealous of that

 

turn on the AC and follow the cold side...from the Condenser the small line will be cold and there will be a stepped connection where it will be hot on one side...that s where your screen is...

too much freon and it gets warmer....you want the lowest PSI you can get away with and the pump not cycle...thats the trick

 

i agree, to much freon and it will get warmer, i found that out myself. just put it in untill it stops cycling.