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Discussion Starter #1
Hey there. Trying to fix as much as I can in my 08 CTS. Noticed my ac is not working. Compressor is not kicking on...

What should my 1st (and following) step(S)?

jump relay? Can I do this from the under the hood fuse box? I don’t know how to tell if those bigger fuses are bad. Mine looks fine though when pulled out.

charge the system and see if low pressure is causing the clutch not to engage?

Any help is appreciated!!

if it’s a bad compressor I think I’ll just go without. I’m guessing they’re expensive and would need a shop?
 

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2009 CTS4 Premium & 2012 SRX4 Luxury
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If you don't already have one pick up a recharge adapter, either just the hose with gauge or recharge kit with a can of refrigerant. Connect it to the low side and check your pressure. If it's low it can cause the compressor to not kick on. If you get the kit you can go ahead and add some. Maybe you get lucky and it's a slow leak and that will hold you for a year or two. If not then it's time to get the can with UV dye and figure out where the leak is. On my son's GrandAm it was leaking from the compressor itself. Bought an entire system off Rock Auto (compressor, dryer, orifice and gaskets - sans condenser) for $150 and took about 2 hours to replace everything and recharge.
 

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Discussion Starter #3
Would that show up on code? Would I need to reset the codes before starting? I didn’t know I could add refrigerant with the compressor not running. Would the gauge be correct with no compressed? Thanks for the reply!
 

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I don't know if low pressure would trigger a code on our CTS. It did not on the GA or other cars I've owned. When the compressor is not running, low side pressure will be higher than when the system is in operation. If the system is at correct charge level the low side pressure will show above normal range. But if the compressor is not turning on due to low charge, then it's drastically low and that will be obvious on the gauge. Connect the kit, start the car and turn the AC on, then just add refrigerant until the low side pressure comes up enough to kick on the compressor. Once it's running then you can get a more accurate reading.
 

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Discussion Starter #5
I tried to jump the relay and I hear nothing. Clutch not engaging. Switched out the fuse with the working horn fuse (same size) and the fuse is fine. Does this mean there’s an issue with the compressor getting power? Or could it still be just lack of refrigerant? Does anyone know if the CTS 08 has codes for this? Going to try to borrow one this weekend...I just want to make sure I’m not buying gauges/cans/dye etc if the system is fine

I’ve been told KTH was the guy to ask...A/C expert??
 

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Discussion Starter #6
I tried to jump the relay and I hear nothing. Clutch not engaging. Switched out the fuse with the working horn fuse (same size) and the fuse is fine. Does this mean there’s an issue with the compressor getting power? Or could it still be just lack of refrigerant? Does anyone know if the CTS 08 has codes for this? Going to try to borrow one this weekend...I just want to make sure I’m not buying gauges/cans/dye etc if the system is fine

I’ve been told KTH was the guy to ask...A/C expert??

@FunkZ need your opinion too!!
 

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2011 CTS Coupe FE3, 2003 Thunderbird, Gone 2013 ATS, 02 Deville
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just go on youtube and watch some videos on how to check the A/C. You can get loaner A/C gauges at many auto parts stores. If the freon is at the proper pressure and the Comp. clutch does not engage it could be a bad fuse, broken wire, bad pressure control switch, or bad clutch on the compressor. If the clutch is bad on the compressor just change the entire compressor and clutch as a unit. If you do remember to put the Comp. OIL in the compressor before you put the compressor on the engine. then you have to vacuum the system and then charge it with freon with the proper amount of freon.
More videos.
 

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Discussion Starter #8
just go on youtube and watch some videos on how to check the A/C. You can get loaner A/C gauges at many auto parts stores. If the freon is at the proper pressure and the Comp. clutch does not engage it could be a bad fuse, broken wire, bad pressure control switch, or bad clutch on the compressor. If the clutch is bad on the compressor just change the entire compressor and clutch as a unit. If you do remember to put the Comp. OIL in the compressor before you put the compressor on the engine. then you have to vacuum the system and then charge it with freon with the proper amount of freon.
More videos.
Shouldn’t my clutch engage when I tried to bypass it? IVe watched tons of videos. Just don’t want to add freon And over charge if the compressor is the problem.
 

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Discussion Starter #10
No worries, the gauges will indicate if you need freon or not.
I guess I should say I wonder why the compressor won’t click on when bypassed, and that makes me think it’s the compressor or something to do with it getting power...

when I put the gauge on, the low pressure line will show me correct pressure with no compressor? I thought by passing the relay was how you got it to accept refrigerator?
 

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How To Manually Engage AC Compressor Clutch
Engaging the AC compressor clutch at home is not rocket science. There are a couple of ways you can fix the problem to bring back the air conditioning system in order.

Method 1: Add More Coolant
What is the most common reason for an air conditioning compressor not to engage? Low level of refrigerant. When the coolant level in the system goes down, the low-pressure switch does not allow the compressor to rotate.

How to manually engage AC compressor clutch when the system is low on antifreeze? Easy. Just adding refrigerant will solve this problem. If your car is compatible with R134a type of refrigerant, attaching a can to the system will override the low-pressure switch and restore the normal function of the compressor clutch.
 

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Sounds like the compressor is in "protect mode" due to low refrigerant.
I attempted to correct this situation once in my less knowledgeable days by replacing the compressor, which didn't work of course, but I did find out about the pressure switch after the fact.

It's probably a good idea to mention to someone attempting to override the compressor without a good understanding about the system, that protect mode kicks in to prevent the need for a compressor, from its continued operation under refrigerant pressures too low to sustain sufficient lubrication. In other words, if you succeed at bypassing protection mode, don't go for a test drive in that mode.
 

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Discussion Starter #14
Sounds like the compressor is in "protect mode" due to low refrigerant.
Thanks everyone. I’m going to order some r134a with dye. Try to recharge it, and at least be able to possibly see the leak (if that’s the problem).
 

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No, you should not just put new freon in it without knowing the pressure in the system. Get the gages and see the pressures.
 

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Discussion Starter #16 (Edited)
No, you should not just put new freon in it without knowing the pressure in the system. Get the gages and see the pressures.
Ya I'll obviously do that first. Pressures? Wouldn't i just be checking the low and making sure its down? I'll have it scanned too. But can't find anywhere online if the CTS would throw a code for low pressure or a bad compressor. Any idea?
 

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Discussion Starter #17
No, you should not just put new freon in it without knowing the pressure in the system. Get the gages and see the pressures.
What are the correct pressure readings when the compressor won’t engage? How do I know if it’s low?
 

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I agree with Long. 90% of the time that I see this, its because of low or no refrigerant due to a leak. You can pick up a set of usable AC manifold gauges for $60. The store should also have glasses and a black light to help find the leak. There are lots of videos explaining how to use the gauges properly. Look closely for oil residue and or dye at all the fittings and the compressor seals. Dirt will accumulate on the area normally. If you have low or no pressure introduce a 12oz can of 134 with the AC turned in. The compressor should kick in with the one can. WM sells it for around $5 a can last I looked. You can buy it with a dye. Check for leaks. If you are lucky and its a hose or o-ring you can replace that fairly cheap. Personally I would replace all o-rings I could easily get to. Replace the accumulator and orfice tube. you can rent/borrow a vacuum pump from the auto parts store to pull the vacuum and check your repair. Use your gauges to recharge with the exact amount of 134. The refrigerant capacity is on a sticker under the hood. Use a digital Scale to measure it. Did it suddenly stop working or slowly stop cooling?
 

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Discussion Starter #19
I agree with Long. 90% of the time that I see this, its because of low or no refrigerant due to a leak. You can pick up a set of usable AC manifold gauges for $60. The store should also have glasses and a black light to help find the leak. There are lots of videos explaining how to use the gauges properly. Look closely for oil residue and or dye at all the fittings and the compressor seals. Dirt will accumulate on the area normally. If you have low or no pressure introduce a 12oz can of 134 with the AC turned in. The compressor should kick in with the one can. WM sells it for around $5 a can last I looked. You can buy it with a dye. Check for leaks. If you are lucky and its a hose or o-ring you can replace that fairly cheap. Personally I would replace all o-rings I could easily get to. Replace the accumulator and orfice tube. you can rent/borrow a vacuum pump from the auto parts store to pull the vacuum and check your repair. Use your gauges to recharge with the exact amount of 134. The refrigerant capacity is on a sticker under the hood. Use a digital Scale to measure it. Did it suddenly stop working or slowly stop cooling?
Thanks for the reply. If I only check the low pressure with a low pressure gauge, or the gauge that comes on the bottle, would that tell me if I’m low on refrigerant? Then at least add some to see if the compressor comes on? I’ve unhooked the battery and let it sit, but still no compressor turning. Was hoping it would clear a low pressure code (if that even exists on the cts 08).

from the videos I’ve watched, I can see how to use the duel hi and low gauges. And charts for ballpark proper pressure Etc. Is this done with the car not running? Would pressure be different running vs. not running when the compressor won’t turn on anyways?

like said earlier, I had no luck jumping the compressor relay. I have to admit I thought just the low pressure gauge would suffice for me. I’m glad I know that with no compressor I need both.

To me it happened suddenly, but it was the first time I’ve used the ac in a while as it’s just getting hot here in Ontario Canada.
 

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The bottles with the gauge will work for checking low side pressure and adding refrigerant. In order to fully diagnose you need to know the Hi side pressure. From what I’ve seen they are overpriced and meant to be a “quick fix”. For the price you could probably get a set of gauges. Without the compressor running your hi and low side should be equalized. Both should be the same pressure. It doesn’t matter if the car is running or not if the compressor is not engaged. The compressor does need to be engaged in order to get your operating pressures. If you don’t mind spending the money and you just want to see if your compressor will engage due to low refrigerant, buy a can and follow the instructions. If It cycles on then you know you have a leak and can find and fix it. To properly pull a vacuum and refill the system you will still need a set of gauges though.
 
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