1990 AC question

[mlipmd]

If the Freon level is that low that the compressor will not engage, you have to bypass or short the low pressure switch to turn on the compressor to get Freon into the system. You will not be able to add Freon to the system unless the compressor is operating using the store-bought cans of refrigerant. And the amount of Freon needed will depend on the low and high pressures in the system, which is way more accurate than saying "add 1lb. of R12". which may be a great excess.
There are many places for leaks to occur, mine was from the Schrader valve on the high pressure line and was cured when I replaced that valve stem. You have to find the leak source before just adding more Freon (which can be done with a leak detector or a UV light dye detector) before assuming anything or just replacing parts hit and miss' till you find it. If you just refill the system you are wasting your time and your money as the leak will persist and you will soon be back where you started from.
You need to do some research and read about the AC system and watch some videos on this, which is way more valuable than just getting some advice, good or bad, on here.
Or bring it to a professional and have someone else look at it.

[jrd1990zr1]

Originally Posted by mlipmd

If the Freon level is that low that the compressor will not engage, you have to bypass or short the low pressure switch to turn on the compressor to get Freon into the system. You will not be able to add Freon to the system unless the compressor is operating using the store-bought cans of refrigerant. And the amount of Freon needed will depend on the low and high pressures in the system, which is way more accurate than saying "add 1lb. of R12". which may be a great excess.
There are many places for leaks to occur, mine was from the Schrader valve on the high pressure line and was cured when I replaced that valve stem. You have to find the leak source before just adding more Freon (which can be done with a leak detector or a UV light dye detector) before assuming anything or just replacing parts hit and miss' till you find it. If you just refill the system you are wasting your time and your money as the leak will persist and you will soon be back where you started from.
You need to do some research and read about the AC system and watch some videos on this, which is way more valuable than just getting some advice, good or bad, on here.
Or bring it to a professional and have someone else look at it.

I understand there are numerous places for a leak to occur, I have every intention of using an UV dye to find the source of the leak. However in order to add the dye, I have to charge the system first. The "add 1 lb. of R 12" comes directly from the 1990 FSM, which is why I asked the question if the system will take refrigerant without the AC clutch engaged. The FSM as written implies it will, I was asking if anyone else had encountered this condition. Additionally there is no mention in the FSM about jumping the low pressure switch. There is a note in the FSM that the compressor should not be operated without freon in the system.