QuestionQUESTION: I have a 95 firebird, air stopped blowing cold. Bought a interdynamics 134a recharger, low end is reading 100psi when air is on. have not tried to fill, can label has a warning for over 60psi low end????
ANSWER: Dave,
The first check I want you to make is whether or not the compressor clutch is engaging. With the engine running and the A/C on is the front plat on the compressor pulley spinning? If you have a dust shield on the front of it, it may appear to be when it actually isn't. In this case, with the ingnition in the run position, engine off, turn your A/C switch on and listen for a snap from your compressor.
I believe your low side is reading 100 becasue your compressor is not engaging. When the compressor is not operating, the pressure equalizes in your lines from the high side to the low side. This is normal. If your compressor is engaging and you are reading 100 on the low side, then we have some serious problems. But I dont believe this is the case.
Going on the presumption that your clutch is not engaging... First thing I want you to check is your A/C clutch fuse. Is it blown? If so, replace it and see what happens. If it is good... the next step we move to is your low pressure switch. The low pressure switch closes contacts within it when the pressure moves above a certain point. typicall 17-22 PSIG. Being that you have 100 psig in the lines these contacts should be closing. So, locate your low pressure switch. It is somewhere on your low side line from your compressor to the firewall. The low side line of course is the one with the low side port on it. Disconnect the harness plug from the switch. With the ignition in run (engine on or off, doesn't matter) and the A/C switch on... with an insulated wire jump the contacts in the harness plug. You should hear the compressor clutch snap. If you do... with a multimeter do a continuity check between the terminals on the switch itself. You should have continuity between them with 100psig of pressure in the line. No continuity... replace the switch (15-20 dollars) Now stepping back a moment to when I asked you to jump the plug harness... if you did not hear it snap... with a voltmeter check the harness plug on the switch for 12 volts. One of the terminals should have 12v.
I will stop there for now. For me to break down check by check would take me about 2 hours to type out and confuse you and I both in the end. By you checking the low pressure switch for voltage, this will lead me in the right direction in the wiring harness. If you do the checks on the switch, and that fixes you up, excellent. If not, do a follow up on this question with the info about the voltage check, clutch snaps/engaging, and fuse. I will get back with you and go from there. That low pressure switch is in roughly the middle of the wiring, so just the check on that will narrow the possibilities down.
I hope I was of a little help. Thank you for the question, and if you need anything more, feel free to ask.
---------- FOLLOW-UP ----------
QUESTION: Correct, clutch is not on. When turning on AC there is a draw on motor but clutch does not engage. Is the ( low pressure switch ) located on the high end? I tried to jump switch, clutch did not engage. All fuses are ok. When you talk about replacing the switch do you mean the one on the high pressure line itself?
AnswerDave,
The low pressure switch is on the low side line. Either on a hard portion of the line itself or the accumulator. The accumulator is an aluminum canister roughly the girth of a soda can with two hard lines protruding from the TOP of it. It is typically located on the passenger side of the engine compartment near the firewall. If you were jumping one on your high side line, this was the high pressure switch. We're not at that point yet.
Did you check this switch for voltage? You should read 12V on one of the terminals of the plug. You said that you turn the A/C on and it creates a draw on the engine? That leads me to believe that the problem may be the compressor itself. Do a voltage check at the compressor plug. If you are reading 12 volts there, ensure that you have a good ground, and if the clutch still refuses to engage, then the compressor is the issue and it needs to be replaced.
Here is the basic rundown on the electrical checks so that way you don't have to do a check, do a follow-up, do a check, do a follow-up. I hate to keep you waiting on me to get back with you, I only have so much free time a day to actually sit down and check on here. As I said it is just a rough check, if you need me to go into more detail about a certain point, please feel free to ask.
>>>The easiest way to check the compressor clutch is to run a hot wire straight from the battery to the power terminal on the compressor itself. With a good ground, as soon as you touch this hot wire to it, the clutch should snap in. Naturally the engine will be off during this. If it doesn't snap, verify your ground one more time and check it again. Still nothing, replace your compressor. Ok, voltage check time. Going to need a multimeter from here on out.
>>>With the key on and the A/C on check your compressor plug for 12v. If you read 12v and the clutch is not engaging... check your ground wire. It may be loose or have built up corrosion that needs to be cleaned. If you do not read 12V here... Locate your high pressure switch (on your high side line) and check this plug for 12V. If you read 12V on one side, use a jumper wire and jump this switch. you should hear your clutch engage. If it does... replace your high pressure switch, it is normally in the closed position and by not sending voltage forward, yours seems to be stuck open. If you do not read 12 volts at the high pressure switch... plug the harness back in and do a voltage check at the low pressure switch. With 12V on one side, if you jump it you should hear your clutch engage. No 12V? Our next step is the compressor clutch relay. Unplug your relay from the box. Check the coil for continuity. You should have continuity. Now check the relay box for 12 volts on the terminal that brings power to your coil. If you have 12 volts there, replace your relay. If you do not... the next step is your thermostat. This is usually mounted directly on the evaporator inside the cab. It will have a bulb that slips into the fins on your evaporator, or mounts to the fins of the evaporator. You should have 12 volts at on of the terminals on it. If you have 12 V, check the thermaostat terminals for continuity. You should read continuity. If you do not, replace your thermostat. The only thing left from there is your control head itself.
I hope this helps you out a bit more. If you need any more help, or I wasn't clear on something in the steps, do not hesitate to ask.
Thank you for the follow up, and the question. Good luck with everything.
