Need AC expertise HELP!

[Blk00ss]

Late last year we noticed my son's '05 not blowing cold. Upon further investigation I discovered the compressor kicking on and off. Made sense, I suspected it was low on R134a. But, it was getting late in the year and cooler so we decided we would deal with the issue this spring. Today I bought AC pro with a gauge. It was low, way low. After pumping a good majority of the 20 oz can into it, we finally got the compressor to kick on/ off, on/ off. It did this for a while and I continued to add refrigerant. Finally the compressor would stay on and the air coming out was gradually getting cooler. But here is the odd part...when the cooling fans kicked on (we were in garage and it was warm), my AC Pro gauge would drop from green, back to white (low) and the compressor would start kicking on and off again. I'd fill it back to green (or close), cooling fans kick on, gauge again goes from green to white (low) and compressor starts kicking on and off again. I finally gave up

Anyone have any idea why the cooling fans kicking on would make the pressure go back down to a level where the compressor won't stay on?

 

[Blk00ss]

Update...my son had an errand to run roughly 15 miles round trip. I told him while he was driving, keep the AC and recirc buttons on just to allow the refrigerant to run through the system. He got home and his AC is much colder, and is staying on.

Maybe it just needed more time for the refrigerant to cycle through the system?

Guess I'll check it again tomorrow. But I have no doubt that it needs more R134a. I believe this system holds 28.8oz dry. And ours was so low when we started this, the compressor wouldn't even cycle on and off. It wouldn't click on at all.

Still don't understand why pressure would drop when cooling fans kicked on though

 

[Joseph Garcia]

Let us know what happens when you inspect tomorrow.

 

[swathdiver]

Update...my son had an errand to run roughly 15 miles round trip. I told him while he was driving, keep the AC and recirc buttons on just to allow the refrigerant to run through the system. He got home and his AC is much colder, and is staying on.

Maybe it just needed more time for the refrigerant to cycle through the system?

Guess I'll check it again tomorrow. But I have no doubt that it needs more R134a. I believe this system holds 28.8oz dry. And ours was so low when we started this, the compressor wouldn't even cycle on and off. It wouldn't click on at all.

Still don't understand why pressure would drop when cooling fans kicked on though

The short wheelbase models with rear AC I thought had a 2.5 pound refrigerant capacity.

Pressure changes when the fans turn on.

@91RS

 

[Blk00ss]

The short wheelbase models with rear AC I thought had a 2.5 pound refrigerant capacity.

Pressure changes when the fans turn on.

@91RS

I belive its 43oz with fonrt and rear AC, which we do have. Which also means, we're still quite low.

I think you're right about the fans. I was not prepared for that. In all the videos I watched, reading I did I did not see antying about the pressure dropping when cooling fans kicked on

 

[Mean_Green]

The bigger question is WHY is it so low? AC systems are supposed to be closed. Low gas means a leak somewhere. How bad of a leak and where it is might make a difference in whether or not a self recharge will last very long.

 

[swathdiver]

I belive its 43oz with fonrt and rear AC, which we do have. Which also means, we're still quite low.

I think you're right about the fans. I was not prepared for that. In all the videos I watched, reading I did I did not see antying about the pressure dropping when cooling fans kicked on

If the AC sticker is still under the hood it'll have the capacity. The generation after yours is what I posted. Let me see if I have a copy of my sticker...

 

[Blk00ss]

The bigger question is WHY is it so low? AC systems are supposed to be closed. Low gas means a leak somewhere. How bad of a leak and where it is might make a difference in whether or not a self recharge will last very long.

I would imagine it has a leak. I mean, its 18 years old. Yes, I'm aware the R134a we put in may just run back out. Its not the end of the world. If that happens, then I'll know there is a good size leak that needs to be addressed. But if we do add R134a, and it blows cold till fall, then that'll work for me.

 

[Mean_Green]

I haven't tried mine yet. There is a note that says the rear seat portion was disconnect, but not why.


I don't know what to expect.

 

[Blk00ss]

Let us know what happens when you inspect tomorrow.

Added another 12oz can. system was still cycling on and off every time cooling fans would kicked on. But once I added enough to where the needle would stay in the green, the system stopped cycling on and off. It needs more as the needle is on the very edge of green. But it blows incredibly cold now, and doesn't cycle off an on. Hopefully it lasts a bit. We'll see. Just glad the issue was obviously related to low refrigerant and not the compressor taking a crap.

 

[RAMurphy]

To properly service the system you should be utilizing a gauge set that measures both High and Low pressures as the system is running and utilizing the attached chart. This will prevent over pressurizing the system and causing additional damage to the A/C system. Understand you are just trying to keep things cool for the summer, but you don't want to cause additional damage. You already have a leak somewhere you don't need to kill your compressor and frag the entire system.

 

[clandr1]

The source of the leak could be the high side service port since the OEM design uses a ball rather than a shrader valve, and over time the ball can deform and not re-seal/seal properly. Do you notice any green liquid (refrigerant) pooling around the inside of the high pressure service port? If not, you'll probably want to add some R134a with UV dye next time you have to charge it so you can try to identify where the leak is.

 

[Blk00ss]

Yeah I'm aware this is a OTC shade tree fix. Its all good, I aint too worried about it. I checked it again this morning, and it seems to be holding steady pressure (for now). And it blows really cold

As for leaks...Not seeing anything significant anywhere. I do recall last year when we realized it wasn't blowing quite as cold that there may have been a bit of die somewhere near the AC switch, which I replaced along with the new O ring that came with it. Not certain thats where a leak was, but I do remember seeing a trace of green dye in that area.

Do those switches tend to leak?

 

[swathdiver]

Yeah I'm aware this is a OTC shade tree fix. Its all good, I aint too worried about it. I checked it again this morning, and it seems to be holding steady pressure (for now). And it blows really cold

As for leaks...Not seeing anything significant anywhere. I do recall last year when we realized it wasn't blowing quite as cold that there may have been a bit of die somewhere near the AC switch, which I replaced along with the new O ring that came with it. Not certain thats where a leak was, but I do remember seeing a trace of green dye in that area.

Do those switches tend to leak?

They can leak. Also check the lines under the RR quarter panel, above the exhaust for the rear AC.

 

[petethepug]

It’s got a leak. Next time you recharge use gas w/ dye in it. You can follow up later w/ a kit that has glasses and a specialty light and look for the neon dye leaking out.

Typically it’s at the schrader valves, compressor shaft seal or joints in the hoses. Beware of repair shops who haven’t worked on these dual systems. A $3-$4h repair can turn into a $2.2k fleecing so they can cover their time & (inexperienced) labor.

 

[Blk00ss]

It’s got a leak. Next time you recharge use gas w/ dye in it. You can follow up later w/ a kit that has glasses and a specialty light and look for the neon dye leaking out.

Typically it’s at the schrader valves, compressor shaft seal or joints in the hoses. Beware of repair shops who haven’t worked on these dual systems. A $3-$4h repair can turn into a $2.2k fleecing so they can cover their time & (inexperienced) labor.

I'm a do it yourselfer. I was raised wrenching on muscle cars and motorcycles so I typically do everything myself unless of course its something I just don't want to deal with. Good honest mechanics are hard to find. I had one that would address issues of mine that I didn't feel like or have the time to tackle, but he retired.

Last year this truck needed some steering attention. I took a chance and used a "reputable" shop to replace our pitman arm and something else up front (can't recall what). Work they did seemed alright, but wouldn't you know it...they didn't bolt the sway bar back and we lost a few of the bolts. They were apologetic, but also didn't offer to buy and replace the bolts. After much arguing I said piss on it, bought the GM bolts myself and reattached the sway bar they left undone. I swear to you....something like this happens every single time I use a shop. Whats so damn hard about doing a once over after a repair? I do it every time I work on something.