I'll get this out of the way first.... 1993 40th LT1, has the auto climate control system (not sure if there was any other), auto with 142K miles

I turned it on today (its actually been cool enough here the last few days to drive with it off) and its now blowing hot air Last time I used it, it was ice cold if I remember correctly.

The AUX fan doesnt kick on with the AC like it used to, but it does kick on when the engine gets to 230.

I'm at a loss here as I know nothing about AC systems, other than I like the air cold not hot

I did the holding of the up and down fan buttons for 5 seconds and 00 popped up, but by hitting the up or down arrows, i could scroll through 1-7, 9-12, 16, 17, 19, 20-24, 30, 31, and 35-37

So, whats a starting point? Its still hot here and I need this fixed!!

TIA

 

1. Does the compressor turn on when you hit the AC?

If not - go for fuses. The lack of the aux fan makes it sound like a controller issue rather than a mechanical problem.

 

I checked the two AC fuses in the panel, and they were fine. Are there any other fuses to check? As far as the compressor turning on, what am I looking for there sound wise? I can say this much, when I hit the auto button, I dont hear any sound changes.

 

Not sure if the 93 has both a High and Low pressure switch, but see if you can find them and "jump" them to see if they engage the compressor.

 

to really fix this right, you will need the helms manual.

I have one for the 1992, if you want to chat on the phone, we can go through some diags???

 

Are those the big red ones? Dad has those for the 93... hmm, that gives me an idea (time to put dad to work )

 

You can PM me with your number or I'll give you mine if you want to talk tech about it over the phone. I'd check 1st to see if it has freon. Then check other items. I've got a service manual for 93 here at work.

 

Thanks for the offer, but I'm headed off to work in a few minutes

 

When Freon levels get low (I'll bet you this is your problem) the compressor will no longer turn on (damage protection). You'll need to add freon. If it is an R12 system (It should say under the hood which type it is) you can either find R12 (expensive) or convert it to R134a. It used to be an expensive conversion but they have found out that R134a will work fine on R12 systems. Get a conversion kit from a auto parts store. You'll get some new adaptors for the AC hoses and an R134a freon with a fill gauge & hose. The only problem is you'll have to empty your current R12. Doing this into the atmosphere can have legal reprucussions so take it to a place that does AC work and have em empty it.

Screw on the new adaptors and follow the instructions for filling. Easy as pie.

 

cheap check

 

Unless converted, your '93 should be R12.

If it's low on gas, there should be a code 9. Once set, the a/c won't operate until it's cleared (disconnect the battery).

Compressor is engaged via a signal from the PCM to a relay. If there isn't a Code 9, check the relay first.

Once the Compressor is on, the PCM monitors the system and turns on the cooling fans based upon a signal from a 3 wire pressure switch mounted on the high pressure line. It gets a 5 volt reference from the PCM and the return voltage varies with pressure (increasing as the pressure increases). Each volt equals about 100 psi and absent a code, the switch may be faulty or system pressure may have exceeded the threshold for safe operation (about 425 psi), at which point, the PCM removes power from the compressor relay. You can measure the voltages to check it out. One should be the 5 volt reference, another return - something greater than 1 volt if it's fully charged, but below 4 volts; the third is the ground. If you have a scanner, it will give you the pressure readout and verify the a/c request signal.

If that switch checks out ok, troubleshoot the low pressure switch mounted on the outlet from the evaporator or larger line back to the accumulator. It shuts off compressor operation when the low side is below 25 psi keeping the evaporator from freezing over. Once a fully charged system is shut off, the pressure will rise and when it reaches 50 psi, the switch contacts close, completing the circuit back to the compressor. Best to use a manifold gage set to see what the actual pressure is, but if you don't have access to one, use a DVM to verify a closed switch with the a/c shutoff. If it isn't closed, and there's no code, a new switch may fix it. It's mounted on a schrader valve, so you don't need to discharge the system to replace it.

 

DING DING DING!!!! We have a winner!!!

NO freon in the system... NONE. Doubt its ever been filled in the 142K miles its seen too. So, didnt have to worry about bleeding off the R12 since there was none, filled it up with two cans of R134a, and walla, cold air!! First can going in, took about 5 seconds to get the compressor to start up (what a welcomed relief that was)

Now I just need to find a guage, see if I need to add any more (conversion kit came with 3 cans) and it'll be all set. That, or I'll just add more if it stops blowing cold

Thanks for all your help everybody

 

You WILL burn out your compressor unless you change the oil. R134a will not circulate the mineral oil in an R-12 system.
It will cool for about a month until all the oil gets out of the compressor good, then it will sieze up.

JS

 

how do you change the oil???

 

When you tried using the system, did the indicator lights above the buttons flash? If there was no refrigerant or very little, the low pressure switch should not work and that would have sent a signal to the controller and set a code 09. If you hit the "Auto" button on the A/C panel, the light above it should have been flashing.

At this point, the best thing to do is to have the entire system tested for leaks. Not using the A/C can dry the rubber seals and o-rings which will cause leaks so the system should be tested. If you want to stay with the R-134a, have a shop do a proper conversion.

If the dryer has never been replaced, it should be done now. The proper oil for R-134a will be installed at the time the shop does the cnoversion.

 

You can get oil in a pressurised can, just like refrigerant and add it on the low side just like the refrigerant. You should add 4 oz at least.

 

Oil capacity is 8 ounces, 4 of which is probably still in the accumulator. If you want it to last, swap that out putting 4 ounces of Ester (not Pag) oil in the new one. Since the compressor hose will be disconnected from the accumulator, put another 3 ounces in it.

If it was low on oil for any length of time, there is probably metal in the orifice. Remove it and clean it or just buy a new one.

Mixing R12 and R134 can raise system pressures (particularly once the outside air temp gets above 90 degrees) to the point that the pressure switch will shut it down - at least you hope it does because otherwise it's going to blow up.