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how do i diagnose my ac system?

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Old Aug 23, 2010 | 01:22 AM
  #1  
Critter's Avatar
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From: fort worth/burleson Tx
how do i diagnose my ac system?

It's blowing hot air so i checked the freon and it was at 18 psi so i filled it to 35 and it's still blowing hott. I don't know where to start with the ac system in finding the problem?
Old Aug 23, 2010 | 01:24 AM
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A common mistake is to add freon if the system is blowing warm. That can potentially make things worse. The best thing to do is to get a dye kit and see if you have a leak.
Old Aug 23, 2010 | 01:29 AM
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i don't think i have a leak, it's just not blowing cold.
Old Aug 23, 2010 | 03:25 AM
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You need to evacuate the system, put in the correct amount of refrigerant, put gauges on it, and then post your results. Until you begin from a known starting point, all bets are off.
You need to post the low side readings and the high side readings. Your numbers do not make sense. This is an R134A system, correct?

Last edited by koolaid_kid; Aug 23, 2010 at 03:27 AM.
Old Aug 23, 2010 | 08:25 AM
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Originally Posted by Critter
I don't know where to start with the ac system in finding the problem?
You can start by telling us if the compressor is running or not.
Old Aug 23, 2010 | 08:29 AM
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Make sure the compressor clutch is engaging. If it isn't, pull the fuse and check it. If the refrigerant gets low enough the computer will stop engaging the clutch. Pulling the fuse will reset it. Make sure your fans are coming on. The A/C won't cool without airflow over the condenser. Are those pressure readings from one of those gauges that come with a can of R134? Was the engine running and clutch engaged when you put in the refrigerant and checked the pressure?
Old Aug 23, 2010 | 12:06 PM
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Update

The clutch is engaging. The pressure is fluctuating between 36 and 39 psi on the low side and i don't have a way of checking the high side. It's blowing at about 70 degrees.
Old Aug 23, 2010 | 09:54 PM
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If you want to do this yourself, you need a set of gauges. Both high and low side. The only alternative is to take it to a shop. I do not wish to sound like a hard azz, but you must do as I outlined before:
1) Evacuate the system. Let all the refrigerant out.
2) Draw a vacuum. Ten minutes should do it, an hour would be better.
3) Fill the system with the exact amount of refrigerant specified.
4) Take the readings, both low and high side.
5) Post your results.
There is no other way with R134A. Unfortunate, but true.
Old Aug 23, 2010 | 11:05 PM
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Originally Posted by koolaid_kid
If you want to do this yourself, you need a set of gauges. Both high and low side. The only alternative is to take it to a shop. I do not wish to sound like a hard azz, but you must do as I outlined before:
1) Evacuate the system. Let all the refrigerant out.
2) Draw a vacuum. Ten minutes should do it, an hour would be better.
3) Fill the system with the exact amount of refrigerant specified.
4) Take the readings, both low and high side.
5) Post your results.
There is no other way with R134A. Unfortunate, but true.
If i do that i'm spending money on the gauge, something to pull vacuum, and the r134 that i'm replacing. If thats what i have to do thats ok because i want to learn how. But, to avoid all of that couldn't i just get a gauge for the high side and go from there? it was working last summer and i know it has the right amount of r134 now that i filled it. So I'm pretty sure there is no moisture in the system and that there are no leaks. There aren't any electrical components i can check 1st?
Old Aug 24, 2010 | 05:37 AM
  #10  
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Unfortunately, no. You do not know how much is in the system because you changed it when you added a can. You have to start from the beginning. Try Harbor Freight if funds are tight. The gauges are about 40, the vacuum is about 15 if you have a compressor, and you can go from there.
Best of luck.
Old Aug 24, 2010 | 11:32 AM
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Is the system blowing outside temp or heater core temp???? Could be a HVAC door issue...
Old Aug 24, 2010 | 11:45 AM
  #12  
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From: fort worth/burleson Tx
Originally Posted by n2ceptor
Is the system blowing outside temp or heater core temp???? Could be a HVAC door issue...
seemed like it was blowing hotter than the outside air with the ac on so i switched to the vent/no ac setting and it stayed the same.
Old Aug 24, 2010 | 01:43 PM
  #13  
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Is the receiver/drier getting cold and building up with condensation?
Old Aug 24, 2010 | 04:48 PM
  #14  
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From: fort worth/burleson Tx
Originally Posted by Marc 85Z28
Is the receiver/drier getting cold and building up with condensation?
I didn't notice anything building condensation. the condenser was about air temperature and everything else under the hood was way hot in comparison, but not cold.
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