Ac not taking in freon

[brahbarian]

My 85 e ac never worked when I got it. It was or appears to have been converted by one of the PO. I vacuumed the system for 45 mins and let sit for another 30 mins and held pressure fine.
When I go to put freon in, it just won't go in? What would cause this?
Also blue ac light didn't work but when I provide power to the pressure switch the clutch would kick on.
I changed out the pressure switch from my known working donor car and it still won't light up the snow flake. I did all the before evacuating the system to refill.

[jeffnhiscars]

There's a micro switch on the middle vent slider and it has to be a good 2/3-3/4 to the right. On early cars the light should go on and off as the micro switch engages whereas I believe on later car the light is on regardless (makes the switch status not so obvious).

You should also be able to get enough refrigerant in without the compressor engaged, to get the low pressure switch to activate. High/low static pressure (mean with the engine off) should be the same and right around ambient (the same number). If you can't get that far something (my guess is the expansion valve) is gummed up.

You did replace the dryer, right ?

[CorvallisBMW]

^all good points. Start with that.

[brahbarian]

No I didn't replace the dryer. I was thinking it would be fine. That would be my next thing to do. A bad dryer would clog up and prevent the system from taking in freon?
I will be also changing the expansion valve since I'll have the system opened up again.

[jeffnhiscars]

Dryers are intended to absorb and hold any moisture that may find its way in to your system. Given the microscopic quantities we are talking about, you can imagine what happens to it when it's exoosed to ambient air. Hence the "cardinal rule of AC recharging"... Whenever the system is opened you replace the dryer. They are (or should be) shipped under vacuum and should be open just long enough to install, seal and vacuum the system.

They are capable of imploding and plugging up your system with the drying agents but I doubt that's your situation. Just sayin'.

A new expansion valve and dryer is a logical next step.

[brahbarian]

Okay. Thank you. I will update when I get everything swapped over.

[e30rapidic]

run 12v to the compressor clutch to see if it will engage, you'll hear a clack. If it does engage, leave it hooked up and crank the car to see if it takes freon then.