Conflicting responces to flushing AC lines...can we clear this up?

fastmonkeywheel · Jul 27, 2006

I've been doing research for the past week about reinstalling the factory air conditioning system in my 90 Mustang. The system was barley working when I bought the car and had the remaining R12 removed by a local HVAC shop. I'm older now and REALLY want A/C in my car again.

I've noticed two responses to flushing the system with mineral spirits. One says NOT to flush the lines because the old oil will help seal the lines for the smaller 134a molecules. It does say to flush the evaporator, condenser and compressor, just not the lines.

The other response was to flush the entire system.

Both seem logical from my limited perspective. Also, does anyone have any experience with the 134a vacuum pump from Harbor Freight? I bought one and have access to an 80 gallon 6.5hp air compressor. Would this provide enough vacuum to boil the remaining moisture? Keep in mind we're getting in the 100* temps around here.

Thanks for the help, after reading all the posts I feel really confident about doing this. Oh, and no half-a$$ work here, I've read the horror stories.

67coupe · Jul 27, 2006

I just did this a few weeks ago. Flushed compressor, evap, and condensor. I bought all new hoses for the following reasons:

1) New accumulator/dryer is a must. They are available with the suction line and accum as one unit. ~$90 at Advance Auto.

2) New orfice is highly recommended. New liquid line contains the orfice. ~ $30 at Advance Auto.

3) I have also heard not to flush and reuse the old lines. Besides, I feel the first two are mandatory and a new high pressure line is ~$35. Might as well replace.

Other than that, there's not much to it. Make sure to get an o-ring kit as well.

Search for the R12 to 134a conversion and look for someone by the name of 'PuterAmI'. I followed his write up on conversions and mine works pretty good in 100+ heat with 50%+ humidity.

Good luck!

90mustangGT · Jul 28, 2006

Being an autotech here in GA, I have done a lot of A/C work. Yes, flush everything, and if you are "in there" might as well replace all the rubber seals. If the lines are good, then they don't need to be replaced. Get all the old oil and crap out of there, and be sure to fill the system with good R134a compatable oil after vacuum. Fill with the factory recomended amount of freon and it should blow nice and cold.

fastmonkeywheel · Jul 28, 2006

I plan on running mineral spirits through the entire system, replacing all the seals with the green ones...got part numbers from one of the write up's, replace the received/dryer/acumulator, add 8 oz of PAG oil (in various spots), evacuate the system for an hour or so and refill with 134a. I'm getting a manifold gauge set so I can do everything properly. I'm going to follow the article by Puter as explicitely as possible. Thanks for the help.

I will flush the entire system with mineral spirits, including the lines. My lines are in good condition so I see no reason to replace them, (except for the one attatched to the receiver/dryer/acumulator)...

BTW, do we have a receiver/dryer or an accumulator? I've heard them used interchangably but also heard that there is a difference...one is on the low pressure side the other on the high...not sure, can anyone clear this up too?

trbkrb · Jul 28, 2006

I got all new hoses with accumulator/dryer and the complete seal kit from www.acsource.com for $124 shipped! I have been planning to swap it all over ONE of these days. I feel that for the price, if the hoses are even somewhat suspect, I'd replace them. One of mine is the original, the others are like 14 yrs old.

As for the accumulator/dryer, it is the black cylinder by the passenger side firewall.

Puter has been very helpful in his posts and write ups.

Good luck on it!

89 Saleen#455 · Jul 28, 2006

Dryer/Receiver and Accumulator are interchangeable terms.

Replace the Accumulator

Replace the Liquid Line (O-Tube line) as suggested.

Flush the remaining components (Condenser, Evaporator, etc.) but do not flush the compressor with mineral spirits. The mineral spirts will destroy the internal seals in the compressor. Instead, remove the compressor, and hold it upside down until all the old mineral oil drains from the compressor. Then add roughly 4oz of PAG oil to the compressor, turn the compressor pulley by hand 20-30 times, and drain all the PAG oil. Repeat this process two more times to ensure that all the mineral oil has been "flushed out".

Reinstall all your A/C componets. Add an 8oz. charge of PAG oil. Pull vacuum for 1 hour. Recharge with R134a.

PuterAmI · Jul 28, 2006

fastmonkeywheel said:
Also, does anyone have any experience with the 134a vacuum pump from Harbor Freight? I bought one and have access to an 80 gallon 6.5hp air compressor. Would this provide enough vacuum to boil the remaining moisture? Keep in mind we're getting in the 100* temps around here.

They are not worth the $10. You really should get the RobinAir unit. It will pull more vacuum with a lot less air supply. Since your ambient is ~100, it may work. I would pull for at least one hour.

Thanks for all of the kind words. Link to writeup...

Fox R134A Conversion

89 Saleen#455... Thanks for catching that about the compressor flushing.

89 Saleen#455 · Jul 30, 2006

Puter is right. Don't waste your money on a venturi-type vacuum pump. They're just not as effective as a conventional A/C vacuum. You can pick-up a fairly inexpensive used vacuum pump on E-bay or at your local pawn shop. I believe you can even rent them at Autozone or some of the larger tool rental centers.

jrichker · Jul 30, 2006

My current vacuum pump is a refrigerator hermetic unit (motor & compressor in one unit). It was a freebe from a local used appliance store. I bolted it down to a piece of plywood & soldered a 1/4" flare fitting on the suction line. It works great, pulls 29" of vacuum in about 10 minutes or less. I have used it several times and have had excellent results.

Conflicting responces to flushing AC lines...can we clear this up?

fastmonkeywheel

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