The indicator lights for my electronic ventilation system started blinking a couple days ago and my A/C compressor won't kick in. I checked the freon charge and it's fine. Any ideas before I take it to the shop?

1990 coupe.

 

Find out the trouble code - depress the fan up and down buttons at the same time for 5 seconds, then depress the auto button. Post the code.

 

Thanks. I'll see what I get.

 

Dont mean to steal your thread... but could anyone tell me how difficult or involved it is to replace a line of the A/C system? There is no freon in the system, and hasnt been any for a long time- In searching for things obviously wrong, i came across two lines (in the engine compartment, passengers side next to the wheel well), that are in bad shape and need to be replaced... how are is this?

 

I checked the code on my vent. display and it gave me a "9" which is the low refrig. pressure lockout. The guy that's doing my work is a decent a/c guy but he's not a pro. He changed me over to r134 a few weeks ago and he seems to think he did it right. My compressor still won't engage. When he put a pressure gauge on the system it read @ 130#. A sticker on top of my blower fan says the r12 refrig. pressure should be @ 2.25#. Okay, where the heck is this 130# coming from? Is this pressure trapped in the system because of the compressor not running or is my system pressure that much higher than what it should be. 2.25 sounds more like static pressure and the 130 sounds more like after compression. HELP!!!! because in one hour we're going to either fix it or break it. Any thoughts on jumpering the compressor just to see if it will run or will the lockout prevent this also?

 

I'm not an Ac man at all but I think the 130 would be PSI...the 2.25 would be holding capacity...as in 2.25 lbs of 12 freon.
I'd cross the low pressure switch out and see what happens ...maybe the 134 install didn't go 100% and it needs a little added.

Jason

 

Assuming galvanic corrosion hasn't played havoc with the fittings, simply unbolt and remove. Do use a backup wrench though, as it's easy to bend aluminum lines. If you intend to fix it, the difficult part may be finding new lines. To my knowledge, the smaller one or high pressure line from the condensor to the evaporator inlet is long out of production and by now, the larger or outlet line from the evaporator to the accumulator may be gone too. An a/c shop can fabricate lines or used is probably available at Contemporary Corvette - www.contemporarycorvette.com .

Replacement lines require new o-rings and you can get a kit that's compatible with R12 and R134 at the Last Detail - www.tld-corvette.com . Save the old ones to match them up with the replacements.

If you are fixing it up, replace the orifice and the accumulator too. Depending on what disabled it - mainly if the compressor seized - you will need to flush out the evaporator and you should consider replacing the condensor too.

To flush the evaporator, spray a good amount of brake fluid cleaner in it and then with a white cloth over one of the pipes, blow compressed air through it. Keep doing this until the cloth is clean and make sure to blow all of the cleaner out of it. You can try to flush the condensor using the same method, but there is so much more area, it's cheap insurance just to replace it.

Once everything is back together, pull a vacuum and make sure that it holds before charging it. Don't be alarmed if the vacuum drops a few points - that's generally just the balance of the water boiling off. To be sure, you can hook the pump back up and a tight system will then hold 28 - 29 ins overnight. Once you're satisfied there are no leaks, charge it up.

 

anybody know what the pressure for the low pressure lockout is?

 

'90 and above use a pressure switch which is a thermistor that increases electrical resistance as the pressure drops. It has a 5 volt reference voltage and each volt that is returned represents about 100 psi. This lets the ECM and a/c programmer know what the system pressure is. If it drops below or above a calculated value, the system turns off. To see if it's operating properly, you need to check system pressure with a manifold gage set and the voltage return with a scanner. To get it running again, erase any trouble codes by disconnecting the battery. Then check your pressures and compare them with pressure readout on your scanner. If there's a difference, replace the pressure switch. It's on a schrader valve, so you don't need to discharge it. If the pressures match, it's either low on gas (and your pressure readings will show this) or there's a high side restriction or air flow problem raising pressures to the cutoff threshold. Again the gages, and whether or not the fans are coming on, will pinpoint the problem.

 

SunCr, JOliver, and everybody else,

Thanks a million for the info. I had left on my journey into oblivion before I got the last reply. We couldn't figure out how to get a correct pressure reading without the clutch engaging initially, so we disconnected the battery. Sure enough, it kicked in intermittently like it had a low charge after reconnecting the battery. Pressed it back up and I'm up and running. One of the new valves was leaking. We checked all connections with a sniffer this time and tightened them accordingly. Thanks again and THIS FORUM IS AWESOME!!!!!!!!!!!!!

I couldn't see cruising to Carlisle with no air available. It gets dang hot out there. I was going anyway.