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I want to add freon - any advise / precautions


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My A/C is not blowing cold.

I bought a can of R134 with a gauge on it.

(the car was converted)

Before I blow things up ...

are there any precautions or traps to look out for ?

Looks like the hook up is on the drivers side up near the front of the engine compartment.



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If converted properly, with new fittings, your 134 hose will only attach to the low side fitting.

If the a/c is working, have the engine running and the a/c on high. This gets the low side pumped down and it is easier and faster to add the 134.

Attach the hose and watch the gage, it is probably in the green....add 134 and the needle should slowly move. Turn off the valve and let the system stabalize and watch the gage. I would try to have the needle in the middle of the green part of the gage.

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Guest Mike_s

Conversions can use either PAG or POE (ester) oils. Check to see if what you purchased also has oil in it. Unless you know what type of oil is in your AC, I'd consider just adding straight 134a, no oil.

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Before you put more in, are you sure it needs any ? The reason I ask is that there is a diverter valve behind the glove box the is servo driven through a rod from the programmer module. If that sticks, you will only get hot air even though the compressor is working.

Unless you have been getting "low freon" warnings or the compressor never comes on, don't just add freon.

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Back a while ago, someone posted some information about a web site where you could either take a coures or test to pass A/C Certification.....I neglected to copy it. I would like to learn enough to top off a system (or just enough to get myself in trouble I guess). A vacuum pump and set of gauges can be had at Harbor Freight for < 100.00. Just think it would be a fun/interesting process to be able to perform.

Anyone remember the information please?

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Nic, I feel the same way.

After some reading, mostly from Arizona Mobil Air aka ackits.com I came to several conclusions.

1. The basic gauge sets all work very well as long as they are not abused by dropping etc.

2. A basic vacuum pump will not ever pull a high enough vacuum you have to spend just a bit more and get a close to professional vacuum pump.

3. You will likely have to get an oil injector to get the proper amount of oil into the system.

4. There always appears to be Freon around and more and more at reasonable prices.

5. Here is the problem as I see it and what has kept me from getting the toys and doing my own. When you have a leak just how do you find it. I never could get a reasonable answer to that question. Soap bubbles only find huge leaks and a freon sniffer is big $$$.

6. I am not at all certain how to take apart some of the specialty hose connections either.

I came to the conclusion that if I never let the system go completely flat I could recharge it for 3 or 4 years before a trip to the garage was required to find and fix the slow leaks and completely evacuate the system.

I could be wrong but these are my conclusions.

Anyone else???

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Guest Mc_Reatta

One of many websites that can get you started:


One of many places to get online Freon cert:


Harbor Freight also has good prices on sniffer and tools to disconnect the more exotic non-threaded connections.

You don't need that high of a vacuum, and you can draw the vacuum for a longer time to remove the air and moisture if you need to.

Leaks can be difficult to find. Besides using soap bubbles or a sniffer, there's also flourescent and UV dyes that can be added to the system to help find leaks. Some techs over pressurize the system to 200 psi with nitrogen to make things easier but that's not for the novice.

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Guest weewilly

I saw a show on motorweek (goss's garage portion of the show) last week about some leak detector flluid you inject into the system and then by using a light which comes with the leak detector that makes the fluid show as bright green almost florecent at the leak. The other interesting point in the show was how to tell if the evporator is leaking. You do this by running the AC then collect the water from under the car and then shine the detector light on the water that drains out. If it lights up you have to replace your evaporator. I wish I could remember the name of the product. Maybe someone else saw the show.

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Most of the reason for pulling a high vaccuum is to get all of the moisture out of the system. Professional systems are designed to save time. A smaller system will work you just may need to let it run for considerably longer. My personal feeling is that when a major component fails, the system should be flushed reguardless and the orifice tube and accumulator/dryer replaced. Any opened fitting should have the O-ring replaced. To me this is just cheap insurance.

The real key is in knowing what is the right amount of freon to add (R12 uses a different amount than R134A). Too much is as bad as too little. You need good guages for this.

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