Air Cond. question

[DJK555]

1988 GMC K2500 5.7L There is a pressure switch near the firewall that has a cap with two wires. Once removed it exposes the connector and also a set screw between the connectors. Can anyone help with an adjustment procedure that can be done without a pressure gauge. I'm trying to reduce the time the compressor cycles. Thanks in advance.
David

 

[mnguy55]

1988 GMC K2500 5.7L There is a pressure switch near the firewall that has a cap with two wires. Once removed it exposes the connector and also a set screw between the connectors. Can anyone help with an adjustment procedure that can be done without a pressure gauge. I'm trying to reduce the time the compressor cycles. Thanks in advance.
David

I have a 94 K1500. It has a similar switch however it was not adjustable (no screw) I put an adjustable one on so I can play around with it. I havent messed with adjusting it yet but from what I understand turning the screw counterclockwise will reduce the shut off pressures and vice vera if you turn it clockwise. When I put the new switch on if cuts out at about 25 and 45 PSI. I am going to try to lower that to about 20 & 40. I dont think you can change the spread between the cut offs (about 20 PSI), you can only move them up or down a little. I may play with this today and if i do I'll write again with my results

 

[DJK555]

I have a 94 K1500. It has a similar switch however it was not adjustable (no screw) I put an adjustable one on so I can play around with it. I havent messed with adjusting it yet but from what I understand turning the screw counterclockwise will reduce the shut off pressures and vice vera if you turn it clockwise. When I put the new switch on if cuts out at about 25 and 45 PSI. I am going to try to lower that to about 20 & 40. I dont think you can change the spread between the cut offs (about 20 PSI), you can only move them up or down a little. I may play with this today and if i do I'll write again with my results

Thanks. Looking forward to hearing how you make out. On mine, anything more than a 1/4 turn seems to make the compressor stay on for a long time. I'm not sure if that will cause problems but it continues to push cold air. Let me know how yours works out.
David

 

[mnguy55]

Thanks. Looking forward to hearing how you make out. On mine, anything more than a 1/4 turn seems to make the compressor stay on for a long time. I'm not sure if that will cause problems but it continues to push cold air. Let me know how yours works out.
David

I played with mine yesterday and it is what I thought. Before adjsutment the cut offs were about 25 and 45 PSI. This caused my AC to cycle too much when on low. I turned the screw couterclockwise 1 turn and the points changed to about 17 and 37. Then it ran too much whne on low and iced up the reciever. I turned it back clockwise 1/2 turn and the points changed to 20 and 40. Now it seems just about right. I dont know much about AC but it seems that you want the compressor to run as much as possible without freezing up so that is where I tried to set mine.