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Guys, I'm still learning this stuff about air conditioning so please bear with me. I picked up a charging unit for a real sweet deal and decided to tackle a older N14 truck.The compressor was toast so I replaced that. It also had a ruptured line on high pressure side. I used the 134A and charged it but the compressor would not start.
I used a jumper to the compressor and it took right off.
After I charged the system, I removed the jump and it still won't go. I tested high and low pressure switch and still nothing. A/C blows cold while jumping.
Fuses are good. Is there a thermal switch or somthing?
I still haven't tested the switch on dash eather.
It's a 1990 international. Thanks.

I can't remember exactly but on my 2000 9900 I had to replaces a control on the firewall , it was a black box with I think 4 lights on the side . It would turn the green one on for working and ect. If I remember correctly we switched it out with a new one to trouble shoot . But I know I cut the wire and jumped it across before the model and it would work . I will be home Sunday night and take a pic for you . If you follow the wires back on the compresser you will find it . I think drivers side firewall Apad control is what it's called if you have one. If you google it ,it will tell you blink codes ect
Hopes this helps

Never mind. Lol. I figured it out.
It was the high pressure switch. But the relay was burnt out so I replaced that and the compressor wouldn't shut off.
I don't know what I was thinking. I tested the switches with the compressor powered by jump. Lol. Newbie mistake I guess, but it's all good now. I just got excited to use this new charging unit befor researching. Thanks.