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Low side pressure reading in zero to negative range

mastersir on Tue May 26, 2009 10:34 PM User is offline

Year: 1983
Make: Ford
Model: Bronco (Full Size)
Engine Size: 302
Refrigerant Type: R134a
Ambient Temp: 80 F
Pressure Low: 0 to Neg
Pressure High: 120
Country of Origin: United States

Replaced Accumulator, Orifice tube and Compressor (FS6). Flushed Evaporator and drew a vacuum of 28 for 30 minutes (vacuum held for 10 minutes). Bypassed low pressure switch and added 3 1/2 cans of R134a for about 42 ozs total charge (80 percent of 52 ozs R12 the system normally holds). The problem is no cold air, Compressor not coming on with low pressure switch connected. My gauges show 0 to neg low side and about 120 high side. The system does equalize to about 75 but it takes about 5 mins to do so. Also AC was not used in about a year. Please help. Thanks.

Chick on Wed May 27, 2009 6:16 AM User is offlineView users profile

Pull your O tube again and check it for debris, if it is clogged a system flush is needed, if not, you have a clog elsewhere.. Most likely the condenser..Hope this helps..

Email: Chick


Freedoms just another word for nothing left to lose

mastersir on Wed May 27, 2009 10:53 PM User is offline

mastersir on Wed May 27, 2009 11:05 PM User is offline

Thanks for the the reply CHICK. I discharged and reclaimed the refrigerant, it was full of moisture. When I removed the line to the o tube, water poured out of the evaporator, not drops but ozs. The o tube was pretty clean just a few black specks. I pulled the accumulator and it too was full of water. I guess the condenser was full of water and when I recharged it, it put out water into the system. I am flushing everything I can and will pull a deep, deep vacuum and replace the accumulator and o tube and refill with oil.
Do you think I need to flush the compressor with fresh oil also?, I'm using POE oil. Will let you know the results. Thanks again for the help.

HECAT on Thu May 28, 2009 6:39 AM User is offline

Originally posted by: mastersir
I guess the condenser was full of water. Do you think I need to flush the compressor with fresh oil also?

Your original post said you flushed, but now it appears you did not flush the condenser? Everything that is being reused needs to be flushed and the flush must be completely removed and every component and hose must be tested and verified to be clean and dry before reassembly. Yes, the compressor needs to be flushed of the contaminated (water) oil. Follow the instructions on the procedures page to oil flush (rinse) the compressor; do not use solvents in the compressor.


HECAT: You support the Forum when you consider for your a/c parts.


Chick on Thu May 28, 2009 6:39 AM User is offlineView users profile

How did so much water get in there?/ Did you flush with water instead of a solvent?/ If you had "any" water in there, you need to change the accumulator again, and flush the system with a flushing agent like Hecats' flush. Never water.. Then use a lot of air to blow the solvents out. Make sure yopu do the evaporator, as they are hard to flush anyway, and you need to get all that water out.. Hope this helps,..

Email: Chick


Freedoms just another word for nothing left to lose

mk378 on Thu May 28, 2009 10:04 AM User is offline

You should look toward replacing almost everything under the hood. If you're going to use the compressor again, run lots of oil through it and tilt it at various angles to try and drain it. I don't know if that model is practical to strip apart, clean internally, then reassemble or not.

If the lines to or from the compressor have any sort of muffler in them they need to be replaced, because it's impossible to get all solvent or water out of those.

Blow out the evaporator with air, then solvent, then air again. Most compressor air comes out of the hose with drops of water in it, so you need to finish with really clean air like would be used for spraying paint, or bottled air or nitrogen.

mastersir on Thu May 28, 2009 8:48 PM User is offline

Okay guys, I do know a little bit about air conditioning. I did not use water to flush out the evaporator ( I used an AC flush and flush gun, followed by lots of compressed dry air), but the reason I did not flush the condenser was it was my friends truck and he was in a hurry to get it done so he told me not to flush the condenser. I should have known better. Now we have flushed the entire system several times, I even flushed the compressor several times with oil and got quite a bit of water out of it also(no dirt or debris was visible). Replaced the accumulator , new O tube (old one had a little bit of debris) and buttoned up the system. I am pulling a vacuum on it tonight and will do it again several times tomorrow. Will check for leaks, charge and let you know the results. I think all the water in the system was in the condenser, the Bronco is normally located in Houston TX (very high humidity). The AC was not run for over a year and had no R12 in the system when I discharged it. I never have seen that much water in a system in all the years I have worked on auto AC's. Once again Thanks for all the help.

mastersir on Sat May 30, 2009 2:13 PM User is offline

I finally figured out where all the water came from. When we charged the system i had the R134a cans in a bucket of warm water. My can tap valve was leaking. We stuck it in the bucket of water and seen bubbles coming out of it (of course the compressor was running at this time also sucking all that water in). I tightened the valve connection several times and stuck it back in the water to check for leaks. It had a bad o ring on the valve. I am still vacuuming the system 30 min on 20 min off and still am getting water in my vacuum pump oil. It's a very milky color and when I drain it and let it sit for several hours you can see the water separate in the bottom of the glass. I have vacuumed the system about 15 times already and there seems to be less and less moisture in the pump oil each time. I do not believe there is a leak because the vacuum stayed at 28-29 overnight. I am going to continue with the vacuum and recharge and let you know the results. I hope that my mistake with the water will help someone else. Thanks again for the help.

mastersir on Sun May 31, 2009 6:32 PM User is offline

Well I finally charged the system - 42 ozs R134a and 7 ozs POE. I also added a UV dye. Results are Low side - 42, High side - 230, vent temp - 45 at ambient 85 (No Leaks found as of yet). The compressor doesn't make any noise. I guess I lucked out on this one. Like they say on this forum DO IT RIGHT THE FIRST TIME AND DON'T DO IT AGAIN. Thanks again for the help.

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