91 Geo Metro A/C Question

[Kersch8]

Just tried using my A/C and get no cool air. Could it be out of refrigerant. If so is that something I can fix? My guess is that it is the old R12, if so, I think it is so expensive can I change it over to the new R134 or is that a major job. Thanks in advance

[geojim]

Changed my '93 to R134a and is working fine:
http://www.automotiveforums.com/vbul...d.php?t=221404

[Kersch8]

Was that a difficult switch to do and can I do it myself?

[geojim]

I brought the dryer and A/C kit at AutoZone and the mechanic put it in. The dryer is the vertical cylinder with the sight glass on top. Changing this was optional, but suggested, by a couple of people. Once the dryer was changed, he change the fitting on the low side of the A/C (between the engine and right fender) and fed in the cans of R134a. Do not feed all three cans, only two are needed. Should be something you can do yourself unless you know of a mechanic/shop that you trust.

[WissNX01]

Did the AC work last time you used it. Sometimes if you have moisture built up inside the AC system, you will reduce your cooling ability

[blackstone]

I just bought a kit at Kmart of all places for $27.99. It contained three cans of the new refrigerant, the gauge and hose, and adaptors claiming to fit any car. I only needed one can since I had the new stuff already. The kit claims to be able to convert any system. The manufacturer is interdynamics, model number RKR-7

[geojim]

My experience with these kits is that we tend to overcharge the system thinking that the more we put in the colder it will get. Doesn't work that way. Better to put less in to start and stay within the pressure range on the kit instructions.

[geozukigti]

Always have your system evacuated before changing to 134a. If there is any r12 in the system, the mixture will coagulate, and turn into brown sludge, and eventually lock your compressor. R134a has a 20% lower saturation rate than R12, therefore, your a/c won't be quite as cold. If you charge the system over 40psi on the low side, the pressure switch will shut your compressor clutch off to save the seals, and compressor from damage. Also, if it drops below 20psi, it will shut off to save the compressor. Lower pressures actually give better saturation rates, but your compressor will click off at high RPM driving. When your car idles@800rpm, and your gauge reads 25psi, your a/c will work. Now, rev the engine to 3000RPM's, and the compressor will click off within seconds, cause the pressure in the a/c system will drop to about 10psi. Now, if you have 37psi in your system, and you rev it to 3k, it will drop only to about 30psi, and still provide you with cool air, possibly with much colder air. Now, rev it to 4000k (freeway RPM@70mph on average) and you'll drop to about 28psi. Still within good safe operating range, and even colder air.
A good swap on a 134a system is a larger condenser, to make up for the less efficient 134a refrigerant. May take some modifying to mount it, and adapt the lines to it, but it will make a signifigant improvement in cooling. If you look at an R12 condenser, and a newer car's R134a condenser, you'll notice the new cars have a condenser that is equal size to the radiator, because they make up for the lack of heat saturation in a smaller condenser.
For a better replacement and almost equal cost to 134a (about $15 more for a full charge), Autofrost is completely r12 compatible. A full kit can be purchased for $50. And has an even better saturation rate than r12, and far better than 134a.
http://www.refrigerantsales.com/autofrost.html

[Kersch8]

Is the Autofrost something that I can do without changing anything? If so where can I purchase this stuff?

[geozukigti]

Yep. It's completely compatible with your existing R-12 and mineral oil system. Just put it in. you can purchase it right from that website that I posted the link to.

[Kersch8]

Thanks, I'll try it