A/C Question

[Turbo Zach]

Here is the deal. My 80 Monte was originally a R12 system with only the low side pressure switch. No high side switch. I converted the system to 134A a couple years ago. New compressor, dryer, and orfice tube. Last year I charged the system and lost track of how much 134A I actually had in the system. I messed with it several times. Let some out, put some in. You get the idea. It would work good at idle or around town, but going down the highway it would blow hot. This year it did not work. So I brought my A/C stuff home. I found apparantly I have a leak. Witch is ok because I needed to start over. I vacuumed down the system and it held vacuum for twenty minutes, so the leak is very small. I charged the system. I found where the system wants to run for pressures. The problem is with the low pressure switch plugged in it wants to cycle the compressor clutch too much. So I put a jumper wire in the low pressure switch plug. It works good now. Held the throttle up and it gets colder and pressures look good. So on to my question: Is there a different low pressure switch for 134A that I should be using? What is everyone else using for the conversion from R12 to134A? Is the systems with a high pressure switch different? Thanks in advance for any replies.

 

[maxi426]

There is a 134A switch available, and I put one in my car just because I was replacing everything anyway. That being said, I did hundreds of the conversions back in the the day, and never had to replace the switch. AC systems are charged by weight, and anything else is just a guess. If I remember correctly, 134A conversions got 80-85% of the R12 capacity.

 

[Mac442]

There’s a screw on the back of the switch that you can carefully adjust with a flathead screwdriver to change the psi that activates the switch.

 

[Turbo Zach]

There is a 134A switch available, and I put one in my car just because I was replacing everything anyway. That being said, I did hundreds of the conversions back in the the day, and never had to replace the switch. AC systems are charged by weight, and anything else is just a guess. If I remember correctly, 134A conversions got 80-85% of the R12 capacity.

I forgotten to mention that I have miss matched components. My compressor, drier, and lines are for a Grand National. I also run at a higher rpm down the road than what it normally would. Three speed with 3:42 gears.

There’s a screw on the back of the switch that you can carefully adjust with a flathead screwdriver to change the psi that activates the switch.

Now you are on to something. Is that what others have had to do?

 

[Bonnewagon]

My wagon is still R-12 but I use an equivalent freon so I didn't have to change the oil or anything. It stays on all the time, blows ice cold, and it never cycles. But my other 134a systems cycle like crazy, especially the Jeep. So please elaborate on the screw so I can try and adjust it. IIRC the switch can come off without loosing the freon, right?

 

[Mac442]

Switch can come off without discharge. The slot for adjustment looks like this photo. Very small turns to adjust PSI. There are more detailed threads on this forum about it.

 

[69hurstolds]

AC Pressure Switch

Is there a GM pressure switch that will fit my 86' Regal that is compatible with 134A and uses the same 2 prong harness? Maybe off of a later model vehicle.

gbodyforum.com

 

[partsbox]

My wagon is still R-12 but I use an equivalent freon so I didn't have to change the oil or anything. It stays on all the time, blows ice cold, and it never cycles. But my other 134a systems cycle like crazy, especially the Jeep. So please elaborate on the screw so I can try and adjust it. IIRC the switch can come off without loosing the freon, right?

Which equivalent freon are you using? Any issues with it? Elsie's AC has a slow leak and I'm down to my last 3 cans of real R12. She'll run cool for a few months on a good charge. Thanks.

 

[Olds G's]

Also very interested in learning about R12 equivalent Freon. Especially if you can just dump on top of the existing R12.

 

[Turbo Zach]

AC Pressure Switch

Is there a GM pressure switch that will fit my 86' Regal that is compatible with 134A and uses the same 2 prong harness? Maybe off of a later model vehicle.

gbodyforum.com

That was what I was looking for. I am sorry about starting another thread on the subject. I didn't know it had been discussed before. I also didn't look too hard, so that is my bad.