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Hi, I have a 1993 firebird trans am. The AC is not working, and hasn’t been since I got the car. We drained all Freon out of the car since it has sat for years in a garage and thought that there would be moisture in the ac line. We hooked up gages to the AC line and it read no Freon before we sucked the line dry. Next we put 1 small 11 ounce bottle in the line, and watched for Leaks. Nothing. After, when the gage read that there was Freon in the line, we turned the switch to AC, but it blows hot air. Also, we read that the fans should kick on and the compressor when the air control switch is set to max AC or AC. Any one know what the problem could be? Thx
 

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The problem is that 11 ounces of R134 does not produce enough pressure in system to kick compressor on. You have to pretty much have a full load of R134 before safety switch will allow compressor to run. I don't know, off the top of my head, how much is a full charge.

So go to the following link and download the 93 service manual. In the hvac section, you will find the charge info and everything else about the hvac. www.mediafire.com/?40mfgeoe4ctti

Ecm will not supply ground to cooling fan relays if ac switch is on, but R134 pressure is too low. If you had an obd 1 scanner that reads real time sendor data, the R134 pressure would be one of the listings of the data stream.

One more thing, with compressor clutch not kicked on, your ac gauge will read much higher than actual pressure in system.
 

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Discussion Starter #3
The problem is that 11 ounces of R134 does not produce enough pressure in system to kick compressor on. You have to pretty much have a full load of R134 before safety switch will allow compressor to run. I don't know, off the top of my head, how much is a full charge.

So go to the following link and download the 93 service manual. In the hvac section, you will find the charge info and everything else about the hvac. www.mediafire.com/?40mfgeoe4ctti

Ecm will not supply ground to cooling fan relays if ac switch is on, but R134 pressure is too low. If you had an obd 1 scanner that reads real time sendor data, the R134 pressure would be one of the listings of the data stream.

One more thing, with compressor clutch not kicked on, your ac gauge will read much higher than actual pressure in system.

So how can I manually engage the compressor so it can suck in more ac? Is it possible to manually engage it so I can add more Freon?
 

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Yes, you can jump the compressor relay to make compressor run. DO THIS ONLY LONG ENOUGH TO GET ENOUGH R134 IN SYSTEM. Compressor will be damaged if run too long with low pressure

Remove compressor relay. It's in the underhood electrical box. Relay terminals should be numbered. You'll find 85, 86, 87, & 30 The terminals you will need to jump are 30 & 87. If you can see the back side of relay box terminal 30 will have a pink wire. This is where relay gets power with key on. Terminal 87 will have a dark green wire. This is the wire that goes to compressor clutch.

So use a jumper wire that connects terminal 30 to terminal 87. turn key on, you should hear compressor clutch engage. Turn key back off. Remove 1 end of jumper wire from relay terminal Set up your charging hose. Crank engine and have it idle. Re connect the end of jumper wire you took off in last step.

Compressor clutch should engage and R134 should go into system. If you have a gauge on your charging hose, charge until you have 40 to 45 psi. If charge doesn't reach that level with 1st can of R134, remove 1 end of jumper. Remove charging hose. And place a new can on charging hose. Put charge hose back on & jump relay again.

If by end of 2nd can, pressure hasn't reached 40- 45 psi, you probably have a leak in system.
 

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Discussion Starter #5
Ya I figured it out. Not enough Freon in system. AC system worked like a charm! Thx for you help!
 
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