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I am working on my 76s AC and I am a little confused about what is wrong with it based on my current diagnosis.
The previous owner converted entire system over to R-134 (except the compressor) and I have receipts on the work done but I am not getting any cold air.
I have cold lines running out of the drier in the fender well into the box, the clutch engages on the compressor when I turn on the fan and roll the *** to MAX AC and full cold, the heater core flap closes when I roll the temperature to cold, the system has a reasonable amount of freeon in it (I did add some to it). I did notice that the heater box in the cab was warm so I plugged the coolant send line coming out of the block to the heater valve and that helped a little on the temperature coming out of the vents but it still isn’t “cold” it blowing about 75 degree air out of it (used a Digital thermometer to verify). Really not sure where to go from here...
I am going to get a heater valve for it but I am trying to find the real cause before it get that.
134 is cheap..i would pulll a vacuum..hoping op put correct oil in and cleaned it out...
inspect oriface screen if. It has one..
buy a set of gauges #1.
Did you use gauge pressure when you added Freon? If you don't have a gauge set, get one. They are cheap at harbor freight.
If it's over filled it will be warmer also. It'll hit the high pressure switch and cycle off. The rapid cycling does not allow for it to cool adequately. In addition over filling can damage the compressor.
I use this chart for pressures because it includes humidity and seems to work pretty well on my 77. Try to hit the low side of things vs the high side. And the lower the better if the compressor will keep running. You'll need to jack the RPM up a bit say 1200 to 1400 while taking the readings to get adequate airflow through the radiator unless you have electric fans.
One other thought is the heater core. If it's still getting hot water to it, flowing or not, it will raise the total air temp in the cabin. I use two shut off valves, one on each hose, to completely isolate the heater core during AC operation.
Op said he plugged the lines..heater
the ‘box’ should be ambient or very slightly above..from conductivity..my factory vacuum shut off works perfect and is same as outside air on vent no ac, or 1 degree higher sometimes..
the only touch im aware of from the service manual is r12..
feel accumulator and the pipe entering evaporator..should be same..and apparently when you get them correct at same temperature..it says add another can!!
the accumulator drier flow is AFTER the evaporator.....
need gauges...but if compressor running should work..
....so I plugged the coolant send line coming out of the block to the heater valve...
I'm suggesting valving both lines. The heater core still gets plenty hot through convection. I've proven this myself, it adds lots of heat to the cabin. Ask your passenger about the heat near their lower legs after an hour of driving.
I know I've heard/read all about not needing to valve both lines on this forum, but in my experience it is simply not true. You must valve both lines to stop the heat.
Back when the system was an R-12 system you could observe bubbles in a site glass on many automotive systems when it needed more freon. The only way to really know what is going on is to observe pressures. The whole system operates on pressure differentials.
I'm suggesting valving both lines. The heater core still gets plenty hot through convection. I've proven this myself, it adds lots of heat to the cabin. Ask your passenger about the heat near their lower legs after an hour of driving.
I know I've heard/read all about not needing to valve both lines on this forum, but in my experience it is simply not true. You must valve both lines to stop the heat.
Back when the system was an R-12 system you could observe bubbles in a site glass on many automotive systems when it needed more freon. The only way to really know what is going on is to observe pressures. The whole system operates on pressure differentials.
While you're at Harbor Freight buying the cheap gauges go ahead and pick up a vacuum pump ..... I have one of those and it has worked like a dream.
Pretty sure this is the one I have. https://www.harborfreight.com/25-cfm...ump-61245.html
While you're at Harbor Freight buying the cheap gauges go ahead and pick up a vacuum pump ..... I have one of those and it has worked like a dream.
Pretty sure this is the one I have. https://www.harborfreight.com/25-cfm...ump-61245.html
not much more...china still...i like robinair..bet similiar
76 AC not blowing cold
