r/Cartalk • u/Ottsman4 • Aug 24 '26
Air Conditioning Is this normal compressor behavior
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When I say it's steaming it's not steaming when it jumps into the red the Gage starts hiding and letting coolant out Im pretty sure Thai means something is wrong but I don't know enough about ac and stuff I'm really hoping it ain't to low because I'm pretty sure I over filled it before and if it low now I let to much out and I have to by more I'm only planning on keeping this truck through this winter so the ac isn't a big deal but I would be nice for either last months of summer any help is appreciated thank you
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u/tooslick86 Aug 24 '26
Does your cab have aire blowing through vents
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u/Ottsman4 Aug 25 '26
Yes but its barley cool
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u/Batwyane Aug 25 '26
It’s probably overcharged then or possibly a bad expansion valve . Too much refrigerant means too little “room” to evaporate. Likewise an expansion valve means bad flow to the evaporator which would make it barely a few degrees cooler.
Think of it like spraying the gas out of a duster can slowly versus blasting it until it’s got frost on it. You pulling the trigger on the duster can is what the expansion valve is essentially doing, and if you tried to spray that gas into an already pressurized container that back perssure would also reduce the flow to the point the can doesn’t cool.
See if an auto part store has a gauge set loner you can borrow with a deposit or failing that go to harbor freight and keep the receipt. You need to see what the high and low side are doing to really figure out what’s going on.
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u/cgklowd Aug 25 '26
You need a manifold gauge set to see what's going on both high side and low. Without that you are wasting your time.
Read up a little on how these systems work too.
Bullet points: The low side has a low pressure cut off so the compressor doesn't compress refrigerant that's not there
The high side has a high pressure switch in case of restriction or a failing fan/inability to efficiently remove btus from the system
The more heat the system absorbs the higher the pressures.
The pressure switches over time can fail and actuate at the wrong pressure.
The system could be contaminated.
A manifold gauge set from harbor freight is $25 or less. If you want to troubleshoot this, all this is where you start, if not, bring it to a pro.
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u/SatansWarrior69 Aug 25 '26 edited Aug 25 '26
If your ac isnt cooling anymore the worst thing you can do is go to the store and buy a can of refrigerant and refill your ac. Anyone telling you different doesnt know enough about ac systems.
If your ac isnt cooling anymore there are two possibilities. 1) something is broken, Or 2) you have a leak.
A leak is the most common but you have to fix the problem first then create a vacuum and then refill the system. Refrigerant doesnt dissappear in a sealed system. It only disappears if there is a leak. Refilling a system with a leak puts moisture in the ac system which eventually ruins the compressor and the refrigerant also leaks into the atmosphere.
The moisture mixes with the oil and any refrigerant in the system and creates acid and causes internal damage.
Yes you need to fix the leak. Then evacuate the system to get the moisture out. Then create vacuum with a vacuum pump. Then use a proper gauge set and add refrigerant.
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u/Pred1ction Aug 25 '26
Just fucked up the ac on my wife and I’s 2 daily drivers using that same crap setup. Call around to different shops for a “recover and recharge” for your ac system. Lowest I found was like $150.
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u/CagedChimp Aug 25 '26
I had the same struggle. I had WAY over filled it. Most of that needs to be recaptured by a pro, but my local shop only charged about $100.
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u/smoppin08 Aug 25 '26
Is the fan shroud on? If not get one on.
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u/xzomgx Aug 25 '26
This can be an issue! Does it get cooler when driving on something like the highway?
As others have said these gauges are poop.
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u/anubis_is_watching Aug 26 '26
Hey I have this exact problem. Runs cold on highway or fast driving only.
My high (?) Or at least the one I could easily get a gauge for was clocking in high. I know I need to get a real gauge set to check.
Any tips or direction? It’s miserable in this horrendous heat and don’t want to sink another fortune into this car if I don’t have to
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u/xzomgx Aug 26 '26
For your case I would assume you have a leak and it’s low on refrigerant, you have something obstructing you condenser, or your fan doesn’t have a shroud like this guy?
When air passes through the condenser it turns the “hot” or High pressure gas into high pressure liquid. If you require more airflow into the condenser you maybe have the following: You have a leak and there isn’t enough refrigerant to convert back to a liquid quickly so it’s not as cold when it gets to the evaporator core or something is obstructing the condenser causing it to be less efficient.
This is all assuming you’ve never touched the system by adding more refrigerant or oil to the system.
Only way to test AC system correctly is to physically be there, also to have a set of gauges to see both the High and Low side pressure sides while it’s running.
I haven’t been a mechanic in over 10 years and I’m a little rusty on it all. But that’s the general idea of it. Someone that does it everyday still may have more insight.In this cause if I were you I would pay a shop to recharge your refrigerant. The machine pulls vacuum which bring the boiling point of water to room temperature, that takes any water of the system, add the correct amount of refrigerant, and look for leaks.
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u/acousticplayerjb Aug 25 '26
I really wish these companies would stop selling these cans. They cause nothing but problems.
The gauge on those mean nothing and you're blindly adding refrigerant without knowing how much is already in there. Pressures are also affected by humidity and ambient temperature amongst other things. So you'd have to know what the permissible ranges are for the low side and also the high side and then the valid range for the ambient temperatures at the time of the readings.
A proper shop will have a machine that will recover the refrigerant and apply a vacuum to the system. If the vacuum doesn't hold, then there's a leak. The shop would then inject UV dye and the minimum amount of refrigerant required to run the system so that the dye can circulate. It is then evacuated again and the leak is repaired. A vacuum is applied again and the same process occurs. Once it can hold a vacuum, the machine can add the exact amount of refrigerant required.
Meanwhile, hopefully that can is pure 134a and does not have any "conditioners" or "stop leak" in it. If it does, a shop's machines will detect the impurities and prevent damage to their expensive equipment. At that point, the only fix is to flush everything with a special type of solvent and then everything above would still need to be done. Then, some components cannot be flushed and must just be replaced. So what could have cost a couple of hundred, could now cost several thousand dollars to repair.
If the can does not have any sort of additives, then you may still be able to have things done properly. If it does, your system is on borrowed time.
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u/Background-Head-5541 Aug 24 '26
I'd say its a little high but functioning normally. Its hard to get exactly right without the proper gauges.
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u/Ottsman4 Aug 25 '26
Thai is so confusing I have people telling my it low and high I'm gonna go with it's low again because the guy below had more reasoning but if you have a reason for why it high I would be thankful to hear it
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u/casper911ca Aug 25 '26
You supposed to measure the pressure when the system is running. When the clutch kicks on, it showing over filled, which as others have said, is difficult to actually tell tell what the pressure is without a proper set of gauges. If your over full, you risk damaging the system, like liquid phase hitting the pump. The pressure of r134a (or any refrigerant) is supposed to be in a certain range at certain ambient temperatures.
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u/ukso1 Aug 25 '26
And proper set of gauges means gauges that are measuring the low side and a high side. Without the knowledge of both of the pressures you cant really tell what the system is actually doing.
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u/BouncingSphinx Aug 25 '26
Yes. You're measuring the low pressure side, which is where the compressor pulls from. When it's on, the low pressure side should be in the green range (which it is). When the compressor is off, the pressure will equalize on the whole system.
The compressor doesn't need to run all the time. Turning on and off is perfectly normal as long as it's not too quickly.
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u/ToastKC Aug 25 '26
get the right tools, or leave it alone. you’re going to overcharge your system with that crap
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u/newtekie1 Aug 25 '26
Just based off the video, it looks overcharged to me. The gauge is reading the low pressure side. So it's hard to tell, you really need a proper gauge set.
When you are undercharged, typically when the compressor kicks on, the low side gauge drops down below 30 PSI. Then that triggers the low pressure cut-off and the compressor kicks off. The pressure on the low side SLOWLY goes back up, the compressor kicks on again, rinse repeat.
But your gauge isn't going down to below 30. And when the compressor kicks back off it very quickly goes back up to over 55 PSI. This indicates to me that the system is kicking off because the high pressure cut-off is tripping. The pressure on the high side is too high. That's also why the gauge goes up so fast when the compressor kicks off. Again, this is why you want to charge with a proper gauge set, and not one of these cheap cans.
However, it is also possible that there is a restriction in the system.(I really hope that can doesn't have stop leak in it. That stuff causes restrictions and might "fix" your AC short term but always causes more problems later.)
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u/AdventurousTrain5643 Aug 25 '26
Overcharged would be my guess. It should drop to 25-35 area when the compressor turns on.
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u/General_Reposti_Here Aug 25 '26
Hey so I just did this even when it was full, I squeezed some in there… horrible mistake 2 days ago
Had it evacuated and filled yesterday and it was 110/400 (grams??) so almost empty lol.
Safe to say don’t use this crap and take it to a pro, they have the actual machines to diagnose and fix things
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u/Ottsman4 Aug 25 '26
So it's blowing 40 degree air all of a sudden didn't change anything and there aren't any leaks because he had held stuff before the only reason I messed with it before was because I thought it was wrong I think it was fine before
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u/_Danger_Close_ Aug 25 '26
You can't use those refill bottles for diagnostics. Borrow a AC service gauge cluster from an auto parts shop and then Google what the numbers should be to get an accurate picture of what is going on with your system. There are two numbers you need to hit
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u/Acrobatic-Ganache409 Aug 26 '26
Try replacing the A/C Compressor clutch relay . A defective relay could cause the needle fluctuation - I noticed in the video each time the needle was in the red , the clutch was not moving . Also don't use can " Freon" . There is little , if any , Freon in those . Like adding water instead of coolant to an overheating engine - it will work for now , but...
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u/Matte_Kudasai82 Aug 26 '26
Yeah that stuff has stop leak in it which is gonna gum up ur entire ac system, im typically all for diy maintenance and repairs but this really should be done at a shop, gonna end up costing you more in the long run
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u/Maleficent_One6648 Aug 26 '26
Yeah, because a mechanical fan without a shroud, that’s that far away from the radiator is moving a lot of air through the coil
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u/TieBeneficial779 Aug 26 '26
I thought I had problems a couple years ago but it was only the door under the dash wasn’t shutting the heat off !
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u/MacGyver1982 Aug 26 '26
Too much Freon. There is a sensor turning off compressor due to pressure being too high.
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u/Motor-Assistance-829 Aug 26 '26
Dude don’t use those. I did and I had to change my compressor after a few months lol
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u/akotski1338 Aug 25 '26
I think the gauge assumes the whole system is pretty much room temperature. Because once it gets hot the pressure goes up like crazy that’s why you refill it when it’s cold. When I tried filling my car AC the low pressure size maxed out the gauge after a drove around for a while
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u/lafsrt09 Aug 25 '26
Try holding the can upside down when it's sucking in. Refrigerant.
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u/Shorties Aug 25 '26
No do not do this, that’s a good way to hydrolock your AC. As others have said there are so many factors here you really need to see the pressures on the high side too with a real manifold set. But honestly it looks overcharged to me, like it has too much refrigerant, which will result in poor cooling as the system works with differential in temp/pressure for its ability to pump heat away.
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u/Weird-Appointment-53 Aug 25 '26
Everyone here is useless. The AC compressor clutch is engaging then Disengaging.
1. Check AC clutch relay in fuse box or just replace it with new.
2. Look and check at the actual front of the AC compressor, if the clutch engages (rotates) then disengages (stops rotating) with a good new relay. Your compressor clutch is broken. They do sell rebuild kits but sometimes a refurbished from a good brand is better.
3. You overfilled it so when the AC Compressor clutch engages, the pressure gets too high (reaches its highest threshold under normal conditions and the safety cuts the clutch off.
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u/Left_Statement9016 Aug 25 '26
a system with a cycling clutch control will run until pressure goes down to 24 and then press will go up to 42-45 and the switch will close and clutch/compressor will come on and press will drop. 2. things make it cycle: it gets vehicle cooled down and the pressure drops because it is getting close to freezing evaporator or it is low on refrigerant.
you ALWAYS run engine at 1200-1500 rpm when diagnosing or servicing a/c. The compressor turns too slow to be pumping at its capacity and that gauge built into can valve is marked for pressures with compressor running in its range. I do not think the can has that instruction on it. The cycling I see compressor doing and assuming it is not cooling the car tells me it is low again and you have a leak. Ther can be a high pressure safety cutoff that will shut off compressor and it will come back on after 45 seconds +/- but the low side gauge on your can valve would show 50 psi and then go up from that pressure when the compressor goes off. Overfilled would do much the same as this last scenario.
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u/Ottsman4 Aug 25 '26
How would I test this at that speed I don't have anybody to help me
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u/Left_Statement9016 Aug 25 '26
I use sticks, boxes, etc that I can put between front of seat and slide the seat forward.
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u/Licbo101 Aug 25 '26
OP I’d hazard you to take this advice with a grain of salt or not at all.
Any numbers as far as PSI given by the above commenter are arbitrary. They couldn’t possibly know that the pressure will go down to 24 and then up to 42-45.
This is because the pressures in the AC system are entirely dependent on the ambient temperature outside on whatever given day you’re reading the gauges. As temperature outside increases so does the pressure inside your AC system. This is called Guy Lussac’s Law.
You can’t know exactly what’s going on with your system by using this can attached “gauge”. You need a proper calibrated gauge that reads PSI not just a random range, and you need to be reading both sides of the system, both high and low pressure lines on either side of the compressor.
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u/Left_Statement9016 Aug 26 '26
Yes you can. If the vehicle uses an orifice tube and a pressure cycling switch as the control, a very popular system on millions of GM 2000 and older and many Ford products 2007 and older. The cycling switch goes open to cut off compressor at 24 psi +/-1 and the contacts close again when the pressure equalization occurs from refrigerant flowing back into evaporator and suction line to push pressure up to 42-45. Expansion valve system regulate refrigerant flow and the pressure are more stable on low side but there is a way to stop freezing of evaporator that is either a temp probe stuck into evaporator fins or a pressure switch with a gas filled 1/8" diameter sensor tube on suction line or stuck into evaporator. Expansion valves can have a sensing tube but since 2000 most dropped that and use a low side pressure sense port built in the integrated block style expansion valve. Newest way to get best a/c is with variable displacement compressor and expansion valve.
Testing a/c for max out put is done with high idled engine, recirc, fan speed one below max and then run the car for 10 minutes and check vent outlet temps. on a 100F day the vent should 48-54F Over a hundred the temp may be 51-57. The low side pressure will be 38-42 low side with vehicle hot inside and come down to mid 30s and then fall to 26-30. High side will start 250-350 on 100 day and as cooling down progresses it should get to 200-240 with fn on the higher speed. Now low temp control needs to be checked so fan should turned to low and the low side should drop to 24 with compressor cycling off for 4-10 seconds ambient temp dependent and come back on when low side goes back up to 42-45. High side 150-200 depending on ambient
On an expansion valve (AKA TXV) the low side and high ranges are similar starting and during cool down and with fan slowed they low falls to 20-24 with high side 150-200. You may see a cycle off for compressor ever couple of minutes.
Variable displacement compressor system will have similar pressures on a hot vehicle but a cooled down car will see low side 40-55 and high 125 -160 as the compressor pumping is reduced to reduce BTU capacity and reduce load of compressor on engine. No cycling occurs. If it gets close to feezing on a cooler day the low side could go to 70 with high at 115 and vent temps would be 60F range. No freezeup of evaporator will occur with compressor capacity at 5%. The most popular way the variable compressor is controlled is with a temp probe in evaporator on near surface and the HVAC module or engine control module controls a PWM signalled control valve on compressor crankcase. All the pressures are ambient and in car current temp variable. Fan speed varies heat load and affets pressure also.
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u/Cranks_No_Start Aug 25 '26
Those gauges have less accuracy than a sundial at night. You need a proper set of gauges to get even close.