A/C

[Mr. Upholster]

Any body know how to convert to the new 134a?I have a 1990 Mark VII that needs a recharge badly, that is if the compressor isn't shot. Should I put the dye in with the lube to check for leaks?? Does it really cool as good as the freon did?? Where is the hi/low pressure sensor located at? I have the guages, But its been years since I did air work, how about a brief refresher with a Mark VII in mind.

[BLUECOLLAR]

Hey MR., most of the parts stores sell a 134 retrofit kit thats basically a bunch of fittings that screw on the existing low and high pressure fittings and allow 134 gauges to be connected. The kit also comes with a container of pag oil and o-rings. I would strongly recommmend replacing the o-rings while you have the system down. Put a light coating of oil on the o-ring on replacement. This will ease installation and help keep the oring from tearing while you slide the line(s) together.

Remember, R-12 is extremely expensive, but USUALLY cools better in a car that its designed to be in. Many people switch over to 134 and have really good luck. My personal opinion is, it all depends on the integrity of the system itself. If the entire system is worn out to begin with, it may not cool to good when its done. If the system is in really good shape, it will pay off to change.
Not knowing how much you remember, I'm just going to hit on the basics and if you need more, just holler!
On every a/c system, theres a high side and a low side. These can be distinguished easily if you remember one rule:

The a/c line coming FROM the compressor TO the evaporator(firewall) is always the "LOW SIDE",or suction side. The "LOW SIDE" is ALWAYS the one you want to charge on. (If you have a set of a/c gauges, you connect the left line,or blue line, to the "LOW SIDE")

The line coming from the compressor going to the condenser(or front of car,looks like a radiator) is the discharge line or "HIGH SIDE".

The cycling switch(a.k.a. low pressure cutoff) is usually on the accumulator. A cycling switchs' job is two-fold.
1)It disengages the a/c clutch (or turns off the comp.)when pressure is low so it won't damage the compressor. An a/c compressor uses freon to build oil pressure,like an engine, so if your running around low on freon, it'll affect your compressor in due time.
2)On an orifice type system, like is on most late model cars with factory air, when the evaporator is getting ready to freeze up, the "LOW SIDE" pressure goes down. The cycling switch is used to "read" these pressures and cut-off, or disengage the a/c clutch, so the system will stay well below the freezing mark. When the a/c freezes up, it gets like a block of ice and air can't blow through it. Freon can't go past the blockage inside the lines either which has a "snowball effect" on the system.

As far as the die goes, it works sometimes, depending on where the leak is. If you would like to borrow a leak detector, e-mail me and lets make a plan.

Adding lube, or refrigerant oil, is mandatory, especiallyu if you have a leak in the syste. Whenever freon leaks, so does refrig. oil. So most of the time, you can find the leaks by looking for a "wet-spot".

Now, have I totally confused you or is it coming back to you? LOL!

[Mr. Upholster]

Bluecollar, Iam right with you, it is all comming back to me. I also remember how important it was to vac the whole system before putting in the freon. I have the old guages will they work with the 134 or will that juice give me phony readings on my antique guages... Might try the retro fit kit first. will the same sniffer that worked with R-12 work with 134?? Bear with me here I'm still getting up to speed.

[BLUECOLLAR]

The gauges and hoses for 134 are totally different. The pressures for 134 are going to be different than that of R-12 and the hoses have different fittings.

If the sniffer is a really good one, it will pick up 134, but 134 is alot harder to pickup than R-12.
As far as the evacuating goes(or vacuuming the system), yes it is very important.

Moisture + Freon = Hydrachloric Acid!

I have worked on a car that wasn't vacuumed out, and every low spot was eaten by the acid and leaked like a stuck pig.

Evacuating at 29in. vacuum, if given enough time, will vaporize water. Rule of thumb is AT LEAST 20 minutes.You can even use the vacuum from evacuation to draw in the needed refrigerant/pag oil into the system.

Maybe a/c 101 should be my next tech post.

[Mr. Upholster]

Thanks again for the info, I will pick up this car on Saturday, can't wait. The owner said the air was working just last year, then it started to get a little less cool, then a little less cool than nothing. My wife dosn't want to ride in the car without air. Maybe thats a good thing.