96 GT Convt. AC Not Blowing Cold

Idlehands78

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Good afternoon everyone. I was reading some posts about my AC compressor not kicking on. I was diagnosing it over the past couple days and now I'm at the end of my knowledge rope.

What I've done.
1. Checked the main fuses, all the fuses are good, no issues there.
2. Checked the in cab fuses, all the fuses are good, no issues there.
3. Threw a gauge on the low side and it read fine. I don't have a gauge to read the low and high side.

Someone suggested pulling and jumping the pressure switch on the accumulator to see if the compressor would engage, low and behold it does. However, it does not blow cold air. With the clutch engaged and compressor running, AC on max, fan on high, ambient temperature air comes out. I let it run for a bit to see if it would get cold, revved the engine to about 1800 for a few seconds, nothing. Not even a hint of cool air. BUT I know the compressor will engage. However, it will not engage from the normally when the switch is connected to the accumulator.

When I did put my cheap gauge on the low side, it did show that the system was on the higher side of normal, but not into a "danger" zone, still green, for whatever that means. It would probably good a good idea to get a hi/low pressure gauge set just to have.

If anyone has any recommendations I'm all ears. It's likely that I'll need to take it to a shop if it needs evacuating, but yeah if I can do it myself that would be awesome. Thanks in advance for your help.
 

cobrajeff96

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I would think that the lines aren't having quite enough pressure to engage the low pressure switch, or just the switch is too far gone itself.

The only real way to be sure of anything (first without dropping a whole bunch of money into the problem) would be to get a vacuum test on the entire system. Usually these problems are because of a leak in the system, there are o-rings on just about every fitting and they just dry up and can't seal anymore.

And if you do get the system recharged, make sure the shop is injecting PAG oil into the system as well in order to keep all the o-rings lubed up.

Also, it's good practice to turn on the A/C every once a while in the winter so that the PAG still circulates for lubricity.
 

07GtS197

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Did you measure the low side pressure with the compressor engaged? If not you didn’t get an accurate reading.

Also, just an fyi for anyone reading, even with the heat on the compressor still runs. So if it’s in storage for the winter, for example, either ac or heat will engage the compressor.
 

lwarrior1016

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You really need a set of gauges to read high and low. If you’re reading the upper range of “normal” on the cheapie gauge with the compressor off, it’s not enough. With a charged system and everything off, I think high and low side will equalize around 100 psi. When the compressor comes on, low side should come down to around 35 or so and high side go up to 250 ish.

I’m betting that you charge that system and it’ll work. Finding the leak would be the next task.
 
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Idlehands78

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Update. So after pulling the low pressure switch and jumping the sensor and getting the compressor to turn on, I decided I would go ahead and replace the low pressure switch, as I wasn't able to even get the compressor clutch to engage at all. I bought a replacement at autozone and put it on tonight. I fired up the beast and turn everything on high. Compressor clutch kicks on, but wont stay engaged. I took it for a quick drive around the neighborhood, still nothing. Compressor kicks on, then kicks off, never staying on for more than 3 seconds. So still not really enough time to even check the pressure on the low side even with a cheap low side gauge.

I would think that the lines aren't having quite enough pressure to engage the low pressure switch, or just the switch is too far gone itself.

The only real way to be sure of anything (first without dropping a whole bunch of money into the problem) would be to get a vacuum test on the entire system. Usually these problems are because of a leak in the system, there are o-rings on just about every fitting and they just dry up and can't seal anymore.

And if you do get the system recharged, make sure the shop is injecting PAG oil into the system as well in order to keep all the o-rings lubed up.

Also, it's good practice to turn on the A/C every once a while in the winter so that the PAG still circulates for lubricity.

After my quick test with the low pressure switch I think your right. A) I think my low pressure switch was back to begin with since I never got the clutch to engage with the old one. B) I really can't check the pressure without legit gauges. Ill see if any of my local friends have a set.

Did you measure the low side pressure with the compressor engaged? If not you didn’t get an accurate reading.

Also, just an fyi for anyone reading, even with the heat on the compressor still runs. So if it’s in storage for the winter, for example, either ac or heat will engage the compressor.

Would you suggest that I pull the sensor and jump it to engage the compressor and then hook up the gauges? Since I'm having a hard time getting the compressor to stay engaged, this would be the only way I can think to get an accurate reading.

You really need a set of gauges to read high and low. If you’re reading the upper range of “normal” on the cheapie gauge with the compressor off, it’s not enough. With a charged system and everything off, I think high and low side will equalize around 100 psi. When the compressor comes on, low side should come down to around 35 or so and high side go up to 250 ish.

I’m betting that you charge that system and it’ll work. Finding the leak would be the next task.

I agree. Since I've only had the car since Sunday, I'm still learning as much as I can about it. What I'm figuring out is that the previous owner likely let this baby site for quite some time. I'm guessing I'm going to be going through a lot of troubleshooting, and enjoying the car as I go. If I can get the AC system to run for the next few months till it cools down a bit (like November) I can start going through the AC system and replacing damaged or cracked parts hunting down a leak. Or at least at that point maybe pressure test it and find the leak. Either way, I'm just hoping to get this part of the puzzle solved.
 

cobrajeff96

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Like I said, take the car to a real A/C shop and do a simple vacuum test. Takes less than a half hour. The test is cheap and easy. That should come first. If there are leaks, replace every single o-ring in the system. Why? Because the compressor has not exploded already and doesn't seem to show signs of exploding. Everything needs to hold a vacuum as step one. I'm betting it won't. But do the vac test, find the leak, replace every o-ring, reseal it all up, do another vac test to make sure... then charge the system and do it at a real shop with the UV dye in it. Then they can spot a leak if it crops up again.

Make sure that the o-rings are the legit green ones meant for A/C. Lube them up generously before you spring-lock them back together. You can do this portion of the work yourself as it'll be a bit time consuming to crack open the spring locks and replace all these o-rings.

Just my advice, it's not gospel.
 
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Idlehands78

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Like I said, take the car to a real A/C shop and do a simple vacuum test. Takes less than a half hour. The test is cheap and easy. That should come first. If there are leaks, replace every single o-ring in the system. Why? Because the compressor has not exploded already and doesn't seem to show signs of exploding. Everything needs to hold a vacuum as step one. I'm betting it won't. But do the vac test, find the leak, replace every o-ring, reseal it all up, do another vac test to make sure... then charge the system and do it at a real shop with the UV dye in it. Then they can spot a leak if it crops up again.

Make sure that the o-rings are the legit green ones meant for A/C. Lube them up generously before you spring-lock them back together. You can do this portion of the work yourself as it'll be a bit time consuming to crack open the spring locks and replace all these o-rings.

Just my advice, it's not gospel.
I appreciate it. I have a reputable shop down the street that does really good work. I'm trying to remain budget conscious throughout my early days of owning this car. But I agree, at some point, it's worth it to just pay the man his wages.
 
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Idlehands78

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Your charge is low. That’s why it keeps cycling
100%. This morning I went out before heading to work, popped the low pressure switch and jumped it and engaged the compressor. Threw my cheap gauge on the low side, empty. I used what little I had left in the can to put something in the system and it started blowing colder than ambient air. Put everything I had in the can in the system, only got up to 15PSI maybe, still in the "low".

Reconnected the LP switch and the compressor would come in for a few seconds and kick off, not enough juice in the system to keep it on. I reached out to a friend that has some gauges, I'll be going over this weekend with a new can and we'll get this thing charged. Then it's leak finding time. I'm sure there's a leak somewhere, but like I said, I have no information on the history of this car, and I'm assuming by the condition it was in when I got it, it had been sitting for quite some time. Fingers crossed that the lube in the can will help with the o-rings sealing and it will last till november when I can get around to changing them all out.

I can't tell you all how grateful I am for the help. That's what this community is for, and you all haven't disappointed.
 

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