QuestionMy 94 Bravada doesn't have power going to the compressor?? It has power going to the tank where you fill the refridgerant but we tested the power at the compressor and there is none? There are several different sensors and my guess would be that replacing one of them might help. How do I know which one?
AnswerBill,
The tank you are refering to is the accumulator. The switch mounted on this is the low pressure switch.
Unplug this switch and with a small insulated wire, jump the 2 terminals in the plug. With your key in the run position (engine on or off) and the A/C switch on... as you jump this you should hear a snap as your compressor clutch engages. If so, this is a good thing. This tells me that we are working in the right area. But this does not mean that your low pressure switch is bad. First check the refrigerant charge. This switch may be disengaging because you have a low charge of refrigerant. If you hook up a gauge and read at least 50 psig with the compressor off... then yes, replace this switch. If you are below this, then your switch is doing exactly what it is uspposd to do and protecting your compressor. In this case... it goes without saying that you have a leak somewhere in your system that should be found and repaired before charging back up. But at the very least your system needs to be charged.
If your compressor still did not engage with the low press. switch jumped... the next step is your high pressure switch. This will be located somewhere on your high side line. It should have 4 wires coming from the top of it. Jumping two of them together will engage your condensor fan (or clutch fan if yours is belt driven) the other 2 will send power on to your compressor. With your low pressure switch still jumped, key in run and A/C on, you can jump these wires together in the same manner. I am not certain of what colors the wires are, but by jumping them this should engage your clutch. If it doesn't check these wires for voltage. If there is none coming into it with your low pressure switch jumped, then there is a break in the wire somewhere between the two switches. If there is voltage coming in and your clutch doesn't engage... plug this switch back in and check the voltage input wire to the compressor. No voltage? Replace your high pressure switch. Voltage to the compressor now and it is still not engaging? That means one of two things. The cheap one: You may need to check your ground wire and make certain that it is free of corrosion and is tight. It may have loosened with the vehicle vibrations. If it has a good ground... The expensive one: your clutch coil is bad and needs to be replaced. In the end it will cost roughly the same amount to replace the clutch as it would the entire compressor. The compressor part will cost more, but it comes with the clutch attached and the air gap set. The replacing of the clutch will get costly because of the time involved in disassembling, reassembling, and setting the air gap correctly.
But in the end, I anticipate you either having a low charge, or your low pressure switch (15-20 bucks) being the culprit. These are typical faults that show up much more frequently than the high pressure switch or compressor.
I hope I was able to help a little. If I can do anything more to help, do not hesitate to ask. Thank you for the question and good luck in everything.
