The AC in my 92 LT1 stopped blowing cold.The Clutch on the compressor is not engaging. I checked the fuse and the connection at the comp. and they're ok. What do I do next? Thanx in advance for any help.

 

First jump the Low Pressure Switch . If compressor runs it's just low on freon. If not check Fuse, Relay and or Control Switch.Make sure you have 12 Volts at the compressor.

 

Yeah i would go with low freon, maybe one of the o-rings is leaking on the pipes

 

For '92, you can't just jump the low pressure switch to get it running. The ECM won't energize the compressor relay if the pressure switch - a 3 wire thermistor on the high pressure line - indicates a low charge. There should also be a trouble code stored which you can access through the Speedo or the Dash Assembly. A quick check would be to clear the Code - disconnect and reconnect the battery - then see if the compressor will engage. If there is some charge left, it should run a few minutes before the code resets and shuts it down again.

 

Thanks alot, I'll give that a shot and see what happens.

 

Why not simple change this over to R-134a if its not already. Check at your local wal mart, schucks,kragen or what ever is in your area. They can help you with this. I would bet that your system is simple low on freon. It will not operate if the low pressure switch is activated. This is a very simple charge to the system to bring it back up. And you will hear over and over R12 and R134a can not work together. We have used this for five years now. Have not had any problems on any of the systems we have charged simply adding the change over charge to the system. Look into it. It works.

 

fnseeker, can you provide any url links to substantiate what you're saying? this would be good news to know

 

Check to see if you are throwing code #28, that means the ECM is not receiving info from coolant temp switch or A/C relay.

 

Changed our car to 134a from R12. I saw the kit on 2 guys garage and they stated it used to be believed the R-12 A/C systems couldn't work with R134a. They now know they do. I had the R-12 bled off at a local shop and added R134a changing out the screw on connections for the low and high pressure hoses in the kit. Added R134a and this sucker has worked like a gem ever since. And it's a helluva lot cheaper than R-12.

Here's what I got..http://www.autobarn.net/inezchrrerek.html

 

R134 is now 10 bucks a can at Autozone - R12 is $15 (get your license at www.epatest.com and buy to your heart's content). You'll need 2 cans and a bit more of R134. You need 3 cans of R12. Don't see any real savings on the gas. Depending on the condition of your system, either will probably need a new Accumulator and getting the junk out of the orifice is a good idea after 10 or more years. Finding why it leaked out and fixing that, at least for me, is probably not bad idea either. Mixing R134 with R12 is a bad idea as your system pressures can get dangerously high (and it won't cool very well either). Fortunately, this doesn't happen very often because most systems have leaked out all of the R12.

 

Thanks SunCr your earlier post was a hit! I reset the ECM and the comp worked for a minute or so (and blew cold air) and then quit.
The previous owner told me he had changed the system to 134a about a year ago so I guess between now and then It's lost pressure. So I am
guessing a recharge with 134a and some sort of leak test are in order?
Are those do it your self charge kits safe as far as not over charging the system? Thanks again for your help!

 

Just wanted to add something...it may not even be whats wrong,but when you first turn on the a/c does the primary Fan run?

It should run to keep the condensor cooled down.I had a strange problem years ago on my Firebird that Class "A" GM technicians couldnt fix.They told me to change the evaporator,the accumulator,the condensor,the compressor and nothing fixed it.It costed me alot of money!!!!

Finally,a friend and I checked everything out and realized the fan was not coming on.A new ecm fixed that..Thats all it was the whole time,the ecm was not signalling the fan to run and the a/c would run hot and not cool down.

 

Depends on Year. The '86 relies on a pressure or fan switch mounted on the high pressure line. Normally closed, it opens at about 220 to 230 psi and signals the ECM to ground the main fan relay. It will remain open until the pressure falls to about 170 to 190 psi. When it closes, the ECM removes the ground from the relay. Absent a/c, the ECM will ground the relay based on the CTS sensor - about 226 degrees which is much too hot for good a/c operation (and is why the a/c system is exempt from Fed Emissions). You need the pressure or a/c fan switch for the system to work right. At 230 psi, R12 is about 160 degrees, and at this pressure (based on the diameter of the gas lines), the system will meter liquid refrigerent into the Evaporator at about 28 to 30 psi or 30 to 32 degrees, ideal for good vent temps. You need a manifold gage set to check out the switch but disconnecting the harness should turn the fan on.

'90 and up use a thermistor for fan control and to monitor system pressure. The ECM sends a 5 volt signal to the switch and the voltage rises with pressure. Each volt the ECM sees is about 100 psi and it generally needs at least .8 volts to keep the ECM from setting a trouble code and shutting the whole thing down. It will also shut it down if it gets a high pressure signal or 4 volts ('89 and below use a separate switch for high pressure control). The ECM will ground both fan relays at about 150 psi (if I remember correctly) or 1.5 volts.

 

My only gripe with R134a is its tendency to not cool as well as R-12 when the humidity is really high.

However, you can buy an additive called "Max Cool" (available at AutoZone, Pep Boys, Kragen's, etc..) that works really well and gets the temps noticeably colder.

 

Just follow the directions, the fill hose has a gauge and you need to make note of the outside temperature though.

 

You have a leak, so you might want to stop by an a/c shop so they can spend 2 to 5 minutes finding it with an electronic sniffer - at this time of year it's usually free (of course they want to soak you for several hundred to fix it - considerably more if it's the Evaporator which for GM, is fairly common). Poop Boys was charging $39 for a leak test in the last ad I saw.

Add refrigerent with the can upside down. Right side up and it will go in as a liquid which can kill the compressor.

On your car, you will have to disconnect and reconnect the battery, then jumper the low pressure switch harness with a paper clip while you fill it. Frankly, I wouldn't add more than 12 ozs. There is still some in it and without a manifold gage set, you can't get a real good guess as to how much. I'd also check for obvious signs of oil loss - on the hood above the compressor and at all fittings and connections. Should you have a high pressure gage (I think most of the kits only give you a low), you want the high side at 2.2 to 2.5 times the temp of the air across the Condensor. With that reading, you're low will be fine (assuming everything else is ok). Also, make sure the low and high side fittings were swapped out when it was converted - from screw-on to quick connect. If not, it's going to be difficult if not impossible to get anything in it until you do this.

 

Ok I went to PEP Boys and bought the deluxe DIY r134a recharge kit.
I Hooked it up to the low side line ( the proper quick connect fittings were installed by previous owner) reset the ECM, started the car and turned the air on. The Guage on freon unit read that it was low but not by much, I gave it a shot of freon for maybe 3 seconds and then let off the trigger to check progress and that put me into the red zone on the guage ! (+ 40lbs) After that the comp quit again. I guess the system shuts down with to much pressure also. When the compressor was running it clicked on and off about every 5 seconds is that normal? What should I do now? Yeah I know, roll down the windows ha ha!

 

Isn't your above statement backwards?

To charge as a liquid you invert the container.
To charge as a gas, container should be upright.

 

Don't think so - the one time I did it right side up, the compressor started slogging liquid - right before it seized. Even the can had an arrow showing that you needed to invert it. My loss, Autozone's gain.


Moto64g: The low side will some times read high while your feeding it gas, particularly if it's cycling on and off. Was your reading after you turned off the flow? If so, it may have a low side restriction - usually the Accumulator falling apart which also plugs up the orifice and leads to the rapid cycling. However, if you got the 40 with the gas going in, try to see what it is with nothing flowing into it and jumper the low pressure switch so it will continue to run. Also, note the outside air temp and repost. It's probably still low and just needs the rest of the can.

 

Outside temp was 85 degrees. That reading was with the flow off. The guage drops to zero when you press the button on the can to let freon in the system,when you release the button you get a reading (as per instructions on can). I ran the self diagnostic check thru the climate control system (found this last night on another AC thread) and it came up with the code 09 low freon. I also see a small amount of oil under the hood above the AC comp. Maybe it just needs more freon. The other confusing thing is when the AC runs after resetting the ECM the air blows very cold.