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Old 08-24-2013, 09:27 PM   #1
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Default Troubleshooting A/C before pulling it

Last summer the A/C in my car stopped working. If my memory serves it cycled on and off but never produced any cold air. I ignored it and just went on driving the car. Since I only drove it top down and only in weather I could tolerate, it did not matter at the time if it worked or not. This summer is basically the same story except I got tired of having the broken A/C. It either works or its getting removed. Before I pull it though I want to truly make sure that it does not work. Currently it does not even cycle; Press the button and nothing happens.

I think whatever freon I had left in the system must have seeped out and I believe there is a sensor that measures the pressure in the line prior to engaging the compressor.

This leads me to two simple questions.

A. Is the AC compressor receiving power through a fuse somewhere that may have blown? I looked in the fuse boxes and didnt see one specifically for the AC.

B. I think I saw a sensor on one of the lines, if I unplug it and short it, will that force the pump to engage? Any danger in that?


Any additional troubleshooting tips are really welcome. If its a minor fix then I would rather just let it be, but if its not going to work then I have no problem pulling it. I already have the shorter belt to retain the power steering.

Thanks guys.
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Old 08-24-2013, 11:28 PM   #2
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Since you made no mention of the year of your car, I'm going to go ahead and assume its 96+ using R134A. If you are still using R12, all directions still apply, but good luck getting freon.

Few things:

1. Buy A/C gauges (harbor freight is fine)

2. Read gauges to verify there is ANY pressure in the system.

3. If yes, the low pressure switch is preventing the compressor from kicking on, so you must hook up freon to the suction side, then manually jumper the switch to force the A/C to start. It will suck freon in. Make sure you use a can of freon with dye/stop leak.

4. See how long it takes before you start having issues again and start looking for the dye leaking out of anywhere in the A/C system.


If you had no freon charge to begin with, you will be forced to pull vacuum on the entire system with a vacuum pump (also can purchase at HF) before introducing freon back into the system.


Honestly, A/C systems are not overly complex and some good google research can teach you what you need to know.
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Old 08-25-2013, 11:04 AM   #3
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I forgot to mention it but you are right it's a R134A system.

I have read numerous times on this board that everyone should stay away from freon refills with sealers in them. I honestly do not know what the problem is since everyone seems to be using them.
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Old 08-25-2013, 01:32 PM   #4
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The stop leak for A/C systems is basically a chemical that conditions the rubber seals within the system. The stop leaken softens them to hopefully reform them into sealing the system back.

I wouldn't have ever guessed it would have worked, but I have used it with success in my wifes car. The schrader valves on both the suction and pressure sides can go south with age as well.

Just recently on my 2000, the A/C stopped working. Lucky for me as soon as I uncapped the cold side, I notice a large amount of oil/residue inside. I bought a specialty tool
Amazon.com: Mastercool 58531 Valve Core Kit: Automotive Amazon.com: Mastercool 58531 Valve Core Kit: Automotive
and was able to replace the valve without discharging my system.

The true A/C guys I'm sure have some valid points on why you shouldn't use A/C stop leak. But they also say you need to do some serious calculations on verifying what pressure you should run, say you shouldn't use HF gauges, or anything else that could be considered "sub-par".

I do things myself, and I've repaired both my car's A/C systems and home A/C systems myself without any formal training and everything works great. I think the professionals make everything out to be more difficult than it is or they wouldn't get any business.
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Old 08-25-2013, 11:26 PM   #5
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Alright, I took your advice and picked up a can of freon recharge. If the gauge on the can is flat I will assume the system will need to be evacuated and thats 150 at least for the vac pump and another 60 for the gauges. Since having AC is not a critical thing, I will pull it instead of investing more money into it. Thanks for the advice, I will let you know what happens.
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Old 08-27-2013, 02:18 AM   #6
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Buy vac pump and gauges learn AC service then charge co-workers for AC service make money buy more speed parts for miata=win.
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Old 08-27-2013, 11:02 PM   #7
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Quote:
Originally Posted by Lee04vr View Post
Buy vac pump and gauges learn AC service then charge co-workers for AC service make money buy more speed parts for miata=win.
Good idea, but has the potential to turn very ugly. The last thing I want to do is be responsible for what happens under the hood of some strangers car. I can only imagine some **** going wrong and then I have to look at this persons face while at the office. Also, lets not forget the rumor mill that will come along with that.
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Old 08-29-2013, 03:42 PM   #8
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Sooooo. The system was apparently empty and before I realized it the whole can got sucked in and still wasnt enough. However, I do have cold air coming from the vents.

Now I know I should have vac'd the system but since I never intended to keep it, I dont care if its perfect. I'll grab another refill and bring it up to pressure. If it holds ill keep it. If it starts to drop, ill pull it.
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