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A/C problems, won't blow cold


 
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nad
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Joined: 18 Apr 2008

PostPosted: Fri Apr 18, 2008 1:23 pm    Post subject: A/C problems, won't blow cold Reply with quote

Okay, well I just bought this Jeep, and the air only blows as cold as the outside air when the A/C is on full blast. So I bought a recharge kit with gauges and filled it up, and it's holding freon fine, not losing any.

The A/C line from the condenser is freezing cold and icing up, but none of the other A/C lines are getting cold at all.

Is this a bad low pressure, high pressure, or cycle switch? Or is there something more wrong. I've read a million different diagnosis to this problem, but I don't know how to narrow it down.

The compressor is kicking on but it's cycling on and off every 5 seconds or so, intermittently. Anyone know what the deal could be?
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DavidXJ
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Joined: 07 Sep 2006
Location: Visalia, CA

PostPosted: Fri Apr 18, 2008 3:05 pm    Post subject: Reply with quote

If you want to know whether the problem is with the "pump switching" issues, such as the high/low pressure switch, or cycling too quick, figure out how to hot-wire the pump so it stays on continually. Then, after a minute or two, if you still don't have cold air coming out of the vents, you have at least determined that it is probably not a problem with the pump coming on and off. But if you do this and then get cold air, you know the problem is the pump isn't being told to turn on and off properly... and good luck with that because it could be one of numerous problems.. (Be careful not to leave the pump permanently on too long or you could freeze the lines and really mess everything up).

The pump could be cycling that often even if nothing is wrong with that system.

Your problem could be simply that the flap inside the blower unit is not switching fully to AC, and it feels like outside air because it's half heat - half AC.
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ecologito
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Joined: 16 Apr 2006
Location: Charlotte NC

PostPosted: Fri Apr 18, 2008 3:26 pm    Post subject: Reply with quote

I have the exact same problem. I took my jeep to a mechanic, 85 bucks and 5 hours later I was told that the condenser had a leak and they had to take the entire dashboard apart to replace. It was going to cost me 1,000 bucks.

I didn't do anything with it. I moved from SC to Ohio so I haven't had to use AC.

they wanted to charge me 800 for labor. They told me that it would take them about 8 hours to take everything apart and put it together.

100 bucks an hour? IS an Nascar engineer going to fix my car?

BTW this was at a AAA shop.
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ThePhantum
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Joined: 23 Jan 2004
Location: I knew it...I'm surrounded by Assholes!

PostPosted: Fri Apr 18, 2008 5:25 pm    Post subject: Reply with quote

The compressor should not cycle that often. When it does, it usually indicates that there is not enough refrigerant in the system for it to maintain consistent high and low side pressures.

There's four things you have to take into account when charging an A/C system:
    1) Outside (ambient) temp
    2) Center vent output temperature (what the A/C is putting out)
    3) Low side pressure
    4) High side pressure

Basically, at a given outside air temperature, the vents should push air in a specific temperature range while the high and low side pressure should be in certain ranges. As an example, (and as per the FSM), at 80F ambient temp, the A/C should blow air between 33-44F, with a low side pressure between 32-41psi and a hi side pressure between 200-260psi.

I'd be curious to know what the gauges are reading...
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nad
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Joined: 18 Apr 2008

PostPosted: Fri Apr 18, 2008 6:34 pm    Post subject: Reply with quote

Well all that technical stuff is jibberish to me. Maybe I'll check the flap under the dash to see if it's not engaging properly.
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djgrayxj
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Joined: 26 Sep 2007
Location: Southern California

PostPosted: Sat Apr 19, 2008 3:11 am    Post subject: Reply with quote

Is the condenser fan [this is the electric fan on your right facing the front] coming one at the same time as the compressor? This should be happening. Also if the system had lost most or all of charge you have a leak in the system [probable the compressor]. If this was the case and you refilled the system without evacuating it first there was probable moisture in it, which is now freezing at the expansion valve stopping refrigerant flow. Phantum or any one else out there with more AC knowledge than I feel free to correct my thoughts. How many cans of refrigerant did you install? From DJ
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ThePhantum
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PostPosted: Sat Apr 19, 2008 6:38 am    Post subject: Reply with quote

You are right on the money. If the system had lost it's charge, you need to draw a vacuum prior to charging it. This not only ensures that there's little to no moisture, but it also evacuates all the air...allowing the system to contain almost pure refrigerant. Since the compressor is cycling on and off, it sounds like there is not enough refrigerant in the system. However, that might be because there is air in the system. So trying to shoot another can in might not solve the problem. That's why I wanted to know what the gauge readings were. By itself, that will tell you a lot about what's going on.

nad wrote:
Well all that technical stuff is jibberish to me. Maybe I'll check the flap under the dash to see if it's not engaging properly.

If it's jibberish, then you probably shouldn't be shooting refrigerant in yourself. Wink The procedure is not just a recommendation....it's a set of specific requirements to not only get an A/C system working and performing correctly, but also for troubleshooting problems.

Here's some more info: http://jeephorizons.com/tech/ac_recharge.html
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nad
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Joined: 18 Apr 2008

PostPosted: Sat Apr 19, 2008 10:58 am    Post subject: Reply with quote

Well I just filled it up until the gauge on the can of refrigerant said it was good. But that didn't help any. The line running from the condensor to the cab is freezing, so I'm guessing there's some type of blockage in the condenser?

Is there anything I can do about it now? Can I evacuate the system and do it again, with vacuum this time? How do you go about putting vacuum in the system?
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ThePhantum
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PostPosted: Sat Apr 19, 2008 2:26 pm    Post subject: Reply with quote

If you read the link I posted above, it clearly states that you'll need a vacuum pump and a manifold gauge set to pull a vacuum on the system. Now that you've put refrigerant in though, you'll need to evacuate that first. Keep in mind that intentionally venting any type of refigerant to the atmosphere is illegal.
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nad
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Joined: 18 Apr 2008

PostPosted: Sat Apr 19, 2008 6:06 pm    Post subject: Reply with quote

I have reason to believe it's the pressure cycling switch on the accumulator, but I'm not positive. Is there any way to change this switch without having to evacuate refrigerant? Or should I just take it to a shop and have them diagnose it and pay them out the wazoo?
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nad
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Joined: 18 Apr 2008

PostPosted: Mon Apr 21, 2008 7:34 pm    Post subject: Reply with quote

Anyone, anyone?
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Code3TJ
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Joined: 01 Jan 2004
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PostPosted: Mon Apr 21, 2008 8:55 pm    Post subject: Reply with quote

nad wrote:
I have reason to believe it's the pressure cycling switch on the accumulator, but I'm not positive. Is there any way to change this switch without having to evacuate refrigerant? Or should I just take it to a shop and have them diagnose it and pay them out the wazoo?

Yes, if it's cycling that quickly, it's probably either a bad connection or the switch is bad. You should be able to replace it without evacuating the system, but you'll still need to correct it (i.e. recharge under vacuum) when you previously filled it.
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djgrayxj
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Joined: 26 Sep 2007
Location: Southern California

PostPosted: Tue Apr 22, 2008 4:40 am    Post subject: Reply with quote

My advice as some one who is now retired but having spent over 20 years working as a plumber for a school district in southern CA. During which time I spent many hours eating lunch with and helping the AC technician if help was needed. Is to give up, start asking friends and coworkers for recommendations as to where they have had satisfactory AC repairs work on their cars. Your $20 dollar repair job was not successful; there fore it is now time to pay the piper if you want a working AC system.

The Phantum tips and questions were not jibberish to me, they sounded like advice from some one that haze over 2 thousand dollars worth of equipment at there disposal and the knowledge of how to use this equipment, which is where I think your Jeep needs to go for repair at this time.

I admire your attempt at trying to correct the problem; a lot of others would not have even tried. Your problem is that the tools to proceed beyond this point is going to become very costly, for starters a good set of hi-lo gages can rune you $100 dollars and the rest of the tools needed goes up in price from their. I just spent the $100 dollars last month to have my Jeep AC system serviced needed 1or 2oz of 134 lost over a 4 year time and 1Hr labor. But now I have maximum cold air discharge again. The next time I may make my first $100 invest in driving comfort in a good gage set.

In my case the adding in a small amount of 134 solved my problem. But in your case it did not, where you go from hear is up to you. Hope my long involved thought process aides you in your next step into cool driving comfort.
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nad
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Joined: 18 Apr 2008

PostPosted: Tue Apr 22, 2008 5:41 pm    Post subject: Reply with quote

Yeah, I think I'm going to just pay up and get it fixed right instead of digging myself deeper. If that's the only thing I'll have to fix on this thing to make it nearly a perfect driver, then so be it. Thanks for the help guys.
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