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Unread 07-05-2013, 10:41 PM   #1
Jeepguy4276
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I checked pressure in my a/c system today due to no cold air......

With the car running and a/c on, pressure was zero. If the compressor is working shouldn't I get some pressure? I added a little refrigerant and still got no pressure reading. I don't see the compressor clutch kick on (the nut in the middle should move I think). Fuse is good and relay is good. Is it a bad compressor or could there be something else?

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Unread 07-06-2013, 04:56 AM   #2
Billwill
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Originally Posted by Jeepguy4276 View Post
With the car running and a/c on, pressure was zero. If the compressor is working shouldn't I get some pressure? I added a little refrigerant and still got no pressure reading. I don't see the compressor clutch kick on (the nut in the middle should move I think). Fuse is good and relay is good. Is it a bad compressor or could there be something else?

You should see the clutch moving when it engages.

The refrigerant sensors will not let the clutch engage if the refrigerant is too low. Best to have an AC shop check the refrigerant charge for you.

You can briefly jump out pins 30 and 87 in the AC relay socket to see the clutch engage but do not run it like that.

The clutch coil could also be burnt out or the air-gap on the clutch could be too large to enable the clutch to engage....fitting shims of the correct value gets the air-gap correct.
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Unread 07-06-2013, 08:45 AM   #3
streetglideok
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Originally Posted by Jeepguy4276 View Post
With the car running and a/c on, pressure was zero. If the compressor is working shouldn't I get some pressure? I added a little refrigerant and still got no pressure reading. I don't see the compressor clutch kick on (the nut in the middle should move I think). Fuse is good and relay is good. Is it a bad compressor or could there be something else?
If the clutch is not spinning, and you have 0 psi, your system is basically empty, and may have a serious leak in the system. Without a vacuum pump, there is no way for you to charge the system as is, you're going to have to take it to a qualified shop. From there, they may be able to find a leak, and/or determine how sound your compressor is. Remember, the R134A is what moves the lubricant(pag oil) in your system. Undercharged systems will not move the pag correctly, and starve the compressor. Owners who take care of their a/c systems, and keep them charged tend to see much lower repair bills.
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Unread 07-06-2013, 02:17 PM   #4
Jeepguy4276
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If the clutch is not spinning, and you have 0 psi, your system is basically empty, and may have a serious leak in the system. Without a vacuum pump, there is no way for you to charge the system as is, you're going to have to take it to a qualified shop. From there, they may be able to find a leak, and/or determine how sound your compressor is. Remember, the R134A is what moves the lubricant(pag oil) in your system. Undercharged systems will not move the pag correctly, and starve the compressor. Owners who take care of their a/c systems, and keep them charged tend to see much lower repair bills.
Yah. I just bought this a couple months ago so I'm trying to get the problems found and fixed. I just got one of the Ac charges at Walmart to see if the system would hold anything or leak out. I figure when I saw the zero pressure it wouldn't work so I only added a little bit to see if the compressor would kick on. I'll just have to take it in and have it checked out. I wanted to avoid the cost because I'm broke.
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Unread 07-06-2013, 02:32 PM   #5
streetglideok
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You'll be a lot more broke if it isn't fixed right, that's the big thing. I know it will ruffle the feathers of DIY'ers, but modern mobile a/c has changed, and there is no place for those quick charge cans anymore. They really should regulate them as they do with R12, restricted to license holders only, if only to protect the public from themselves. Look for this to happen in the future anyways, as R134A has been deemed a strong greenhouse gas, made illegal in Europe.
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Unread 07-07-2013, 03:07 PM   #6
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If you have the recharge can with oil and you follow the directions, you can charge the system and it shouldn't damage it. That said, you don't know what happened to the refrigerant and a component could've been removed for some reason and put back together. In that case definitely have a pro look at it. Don't take it to some grease monkey shop like lube stop, they rarely have an ase certified mechanic, just a machine and a guy with a cfc certificate. Not the same thing. It should be a shop that can make repairs, not just service the system. There is a difference.
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Unread 07-07-2013, 03:21 PM   #7
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If you have the recharge can with oil and you follow the directions, you can charge the system and it shouldn't damage it. .
That's asking to destroy the system. For starters, does those cans hold pag or ester oil? If it is pag, what weight of oil is it? Wrong oil can munch a compressor. Next, if the the system already has the proper amount of oil, and you add more, that will cause more problems as well, and does it say how much oil is in the can? Finally, you can not just put a charge in a system without pulling it down to 29-30" of vacuum. To do so will lead to an impure charge, poor performance, possible icing of the orifice tube, and a blown compressor. Hence the need for more regulations of the product.
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Unread 07-08-2013, 06:41 AM   #8
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First of all, R134A is not a blend. Yes, you have to pay attention to weather it's PAG or POE oil, there won't be any mineral oil in R134A. PAG and POE are both synthetic oil. The amount of oil in those cans is the estimated amount that leaks out along with the refrigerant. If the compressor has been drained, such as with removal, it will most certainly ruin it. If the system were to leak down to the point that the system doesn't operate well then it should be fine. All systems leak a little over time and there's nothing wrong with topping off as long as it's not an azeotropic blend, the refrigerants that compose the blend leak at different rates and all of it will need to be removed, the system placed into a deep vacuum and the charge weighed in as a liquid. Not to mention, belt driven systems are much more forgiving that hermetic systems as long as there's enough oil.
By the way, you took my quote out of context, I think I mentioned the fact that the system was completely emptied and should be checked by an ASE certified mechanic.
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Unread 07-08-2013, 06:56 AM   #9
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First of all, R134A is not a blend. Yes, you have to pay attention to weather it's PAG or POE oil, there won't be any mineral oil in R134A. PAG and POE are both synthetic oil. The amount of oil in those cans is the estimated amount that leaks out along with the refrigerant. If the compressor has been drained, such as with removal, it will most certainly ruin it. If the system were to leak down to the point that the system doesn't operate well then it should be fine. All systems leak a little over time and there's nothing wrong with topping off as long as it's not an azeotropic blend, the refrigerants that compose the blend leak at different rates and all of it will need to be removed, the system placed into a deep vacuum and the charge weighed in as a liquid. Not to mention, belt driven systems are much more forgiving that hermetic systems as long as there's enough oil.
By the way, you took my quote out of context, I think I mentioned the fact that the system was completely emptied and should be checked by an ASE certified mechanic.
I never referenced a "blend". I would say you have taken my post out of context. Ester is an oil based lubricant, PAG, is glycol based, totally different, like oil to water. They are not meant to even be mixed. There still is the issue with the correct viscosity of pag used, and anyone with experience in mobile hvac knows, no system is truly empty unless it is under deep vacuum. We also know the vast majority of the crude being peddled in those cans has sealer, and again, anyone with experience knows the headaches that junk creates. If your system has leaked down, the only way to service it is to have it fully evacuated and recharged. There is no topping off of the newer systems and their reduced capacities.
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Unread 07-08-2013, 12:45 PM   #10
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Ok, I don't want to be in a pissing contest but I looked up oil compatibility and POE is compatible with PAG. Neither are compatible with mineral oil. PAG is the OEM oil for R143A and Mineral oil was the oil for R12. POE is sometimes used for retrofits because it can be used in a system that had mineral oil in it and it's less damaging to the system components. I couldn't find any info about viscosity but I don't think there is more than one for Auto A/C systems. Maybe for mobile refrigeration systems but that's a whole different breed of cat due to the range of temperatures that are covered. The oil that's in every can of the stuff I bought to top off a couple vehicles I owned had PAG oil in them and an o-ring conditioner, not a leak sealer. That seems to be what was out there when I was looking.
There is no substitute for skilled labor, you are correct but sometimes the cost of A/C repairs is more than the vehicle is worth or the person that owns the vehicle can't pay it. Most of the time, if it's a refrigerant pressure issue, the system only requires a few ounces to top it off. Hardly worth $300.00 to have the system completely checked out and recharged.
If the system has zero pressure, it most likely has air in it and needs to be evacuated but if the pressure is just low enough that the pressure switch is keeping the compressor off then mine get topped off.
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Unread 07-08-2013, 02:13 PM   #11
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I couldn't find any info about viscosity but I don't think there is more than one for Auto A/C systems. .
There actually is a few different PAG oil weights.Sanden is the most used AC compressor in Jeeps and either use a 46,80,or 100 weight oil and there is also a 150 weight PAG oil also.
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Unread 07-08-2013, 02:15 PM   #12
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Wow, that's thick stuff.
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Unread 07-08-2013, 06:20 PM   #13
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So do you think shops really pay attention to the weights and what is specific to the vehicle? I wonder if even the good Ac shops just get the job done as they see proper.
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Unread 07-08-2013, 06:36 PM   #14
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The relevant info is on a sticker under the hood and in the service manual. A good shop, maybe. Someplace like lubestop, probably not.
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