widebody2

Hey guys, what have you paid to have your AC recharged. I took mine apart to do a single and fmic. I have it back together but the condenser is at a horrible angle and really isn't going to get much flow to it. Please don't tell me how to set it up since it won't be getting changed. I am not sure if the ac will really work or not after getting it recharged and I am wondering if its worth trying it.

DaleClark

iTrader: (55)

It will depend on your area and what the shop charges as far as cost. Also, if you undid any lines on the AC system, you HAVE to put new O-rings on the fittings that were opened up - the O-rings are one-time-use deals. They're under a LOT of pressure and have to be perfect - we're talking HUNDREDS of PSI!

That said, I've had my AC pulled to a vacuum and fully charged with R-12 for $120 here locally - that's a very fair price. That's all done, tax, out the door too.

Find a shop that specializes in air conditioning repair rather than a jack-of-all-trades shop.

Oh, if you need O-rings, get new Mazda parts - call Ray Crowe up and get whatever ones you might need. Put some dielectric grease on the O-rings when you reinstall them, and tighten the fittings up SNUG, not over-tight.

Dale

widebody2

Thanks for the tip with the O-rings. I was going to reuse the old ones. $120 isn't bad at all. I was affraid it was a lot more

iluvmy3rdgen

Yeah they sell a UV lube for a/c systems, it's light green. Get that and oil the o'rings. If it's the older a/c system r134 it's a lot more money then r12. I worked at a shop and the older system was close to 160 to re-charge. But don't forget to tell them that you had the system apart.

They have to evac the system, put vacumn to it, turn the pump off and watch the guage, the needle should hold steady for 15 minutes then they put a couple ounces of the oil into the system with a special tool that just winds down and releases the oil into the vacumn which circulates. Then then charge the system, start the car, run the compressor and adjust the amount in the system to have a healthy Hi and Lo side.

If the condensor is at a tough angle, try to get a slim fan on it, like a F-A-L setup, wired into the stock a/c fan.

Hope this helps.

BlueRex

I thought it was the R12 that was the more expensive, discontinued (in 1995 IIRC) refrigerant.

iluvmy3rdgen

Yeah R12 was the older system and R134a is the newer system, sorry for the confusion. The R12 costs near $90 a lb near me and the r134a is like $9 such a difference.

iluvmy3rdgen

Yeah R12 was the older system and R134a is the newer system, sorry for the confusion. The R12 costs near $90 a lb near me and the r134a is like $9 such a difference. There are conversions avaible to make your system R134a if you'd like to be up-to-date and have an cheaper re-charge.

BlueRex

It would be a cost effective option since I believe the conversion kits run only $30.

All the kits really contain are new fittings and R134a refrigerant.

iluvmy3rdgen

Yeah, the kits are definetly worth it, but I wouldn't expect any cold air to come out of a system that wasn't evacuated and tested for optimum refridgerant.

BlueRex

That's because the condensor designs are different for each system correct?

A friend of mine used one of the conversion kits on his miata. He was happy with the results, but that could be because his a/c was basically useless before.

DaleClark

iTrader: (55)

The R-134a conversion will NOT get you ice-cold AC that the system can do with R12. An FD with a properly functioning R12 AC system is a pleasure - gets super cold super quick, and actually puts VERY little load on the engine. I'd stick with R12 - it's still reasonable to get the system charged with R12. If it was $500 for a charge, yeah, I'd look at R134a.

Dale

tzbfwt

iTrader: (1)

OK - insert all legal disclaimers here - I have no money, so don't sue me. an appliance repair guy I know told me that propane can be used as an R12 replacement.
I know it works because my garage (beer) frig is currently running propane (old frigs use R12). It has a small leak somewhere- so instead of fixing it - I just recharge it with propane every few weeks. We are talking tiny amounts here - I think my frig holds 9 oz of R12 or propane

should you try this on your car? Don't know - the expansion/compression cycle is the same in all R12 systems - so it should work. But what would a propane leak do when it found a nice cherry red turbo or exhaust pipe? Don't know - but I do know the propane/air ratio has to be just right to ignite. My garage has a natural gas heater - kicks off/on all day & night - haven't blown it up (yet) But the frig nevers leaks enough to smell the propane.

Now - you guys make me smart - when did the third gen convert from R12 to R134A? I know the 93 1/2 Camaros were one of the first GM products to use R134A, so I suspect the RX7s converted in this timeframe.

And whatever you use - save yourself the $100 recharge fee - just buy the $10 Harbor freight vacuum pump - vac the system and recharge with R134A (or propane?) If you use propane, you can just charge and bleed it several times to flush the moisture out of the system.

And if FD's start blowing up all around the country?? - I guess mine just got a little bit more valuable... hey hey

dgeesaman

iTrader: (7)

Propane is an interesting idea, but I'll bet it doens't work as well. There are efficiency curves and stuff in thermodynamics texts that clearly show why R12 does its job so well. R134a is significantly behind, given the same amount.

It's also dangerous as hell. I know it's not a tremendous volume of propane, but if the car is in even a minor accident it could/will break the lines and leak the propane. As it leaks, if there is something hot or sparking, you can be sure that it will ignite before completely dissipating, and make a blowtorch at the leak.

As far as the leak in your garage, hey, that's your business. It probably won't ever catch fire, but an electrical short in the fridge would be pretty scary. I'm just glad you're not my neighbor.

Some states are very tough to get your own R12. I would put in new o-rings and have shop do it.

Dave

tzbfwt

iTrader: (1)

yes - you are correct - an accident scenario with a propane leak and a spark could be a bad situation, as could a gasoline leak in the same situation - and then we have those darn airbags full of space shuttle booster fuel too...

as for not being my neighbor - OK - I'm sure none of your neighbors have propane gas grills on their patios, right? and none of them ever, say smoked a cig near it or used a propane torch to solder copper plumbing in their houses either...

there are many risks in this world - take your pick. Use R134A - it's alot cheaper than it used to be.

Jim

iluvmy3rdgen

Don't listen to tzbfwt widebody for what every you do. An a/c system goes from extreme high temperatures and high pressure to a sudden expansion valve that releases all the gas to make the "cold" air happen. The sudden change from high to low pressure cause the chemical to change hundreds of degrees (upwards of a 300 degree change F) which will occur, using a flammable gas is just stupid, why do you think the old systems are no longer in use. The only reason R12 isn't in use any more cause it was less ozone friendly NOT FLAMMABLE, do it safe and do it right. Having a Hi side filled with propane and having a slight leak is like the old Blimps that used to use hydrogen.


KA-*******-BOOOOOOOOOOM

DaleClark

iTrader: (55)

Few things -

The '93-94 RX-7's use R12, the '95s use R-134a. From what I've heard, the '95s didn't have the coldest AC - it's better than a 134a conversion, but still not as cold as the '93-94s. That's part of the reason I bought a '94 and not a '95 .

The air-powered vacuum pump from Harbor Freight is CRAP. I bought one some time back - first off it's JET PLANE loud, and second it can't pull a full, deep vacuuum - it doesn't get down low enough to properly pull all the moisture out of the system. It's a waste of money. You'd be better off spending a few bucks on a used vacumm pump off Ebay, especially a quality brand like Robinair. Or, just have a shop do it for you - again, I had a full vacuum and R-12 charge for $120 - you just can't beat that.

I think it's already been well said, but I would NEVER run propane in an AC system. One of the things you can likely get away with, but if you *do* have a problem, it could be your car or your life. Not a gamble I'm gonna take to be a cheapskate - I'd wait a bit and save my money, then do it right.

Dale

DamonB

I have always used an air compressor to pull the vac. Remove the inlet filter from the compressor and then rig some fittings to connect that to the a/c. Works like a charm and many people have big air compressors.

I replaced all the seals and converted my car to 134a a couple years back. It does fine until it gets really hot (which is often in Texas) and then it takes a while to cool the car if it's been parked in the sun. My original 130,000 miles a/c compressor is also a little tired so I have a new compressor waiting to go on. Once I leak check it and pull a vac I'm going to recharge it with R12. I plan to replace the expansion valve for the hell of it to be certain everything is ready to go.

tzbfwt

iTrader: (1)

Dale - thanks for the tip on the vacuum pump - did you have a set a gages hooked up when you were using it? What kind of vacuum did it pull? 10 inches? I think my gages go to 30 inches of vacuum- and I'm sure a good Robinair would pull that - but if the HF jet engine will pull 10 inches - that would be good enough for me... I figured it was an orifice based pump - so you need a healty air compressor to power it - what size did you use? I watched a friend use one - but he had a 230V compressor - a big one - 10SCFM big at least. He didn't have gages - so don't know what it pulled. I've also heard that you can salvage an old compressor out of a frig and use it as a vacuum pump. and you should change your filter/dryer if the system has been open for a while - before you charge it.

Now - DONT USE PROPANE DONT USE PROPANE DONT USE PROPANE

there I've said it three times - but you guys better never go to Canada (they run propane power Silverados all over the place. Pressure? Try 3000 PSIG tanks in/under the bed. for that matter - stay out of most big warehouses too - propane powered fork lifts...

as far as the post above about the refrigeration gas under going some chemical change at the expansion valve?? wow - I hope you don't have an engineering degree if you believe that one... all refrigeration cycles I ever learned about involved a gas that boils at room temp and can be compressed to a liquid under a few hundred PSIG - I think a good R12 system runs at about 250 PSIG. when the liquid vaporizes in the evaporator, it absorbs heat, then it gets compressed again - runs thru the condensor to reject the heat, then back to the evaporator/expansion valve. Simple - R12 and propane just happen to have about the same boiling point - so they both work. If it were my car - I'd probably do a fill with propane to check out the system - if it stayed charged, I'd vacuum and refill with R134A.

Geesh guys - propane is not the Devil, I'd be much more concerned with those fuel and oil lines right above my cherry red turbos - didn't Broken 93 just catch his on fire with an oil line leak?

DaleClark

iTrader: (55)

The Harbor Freight vacuum pump pulled about 20" of vacuum. You really need to get a hard vacuum, closer to 25-28". The reason is water will boil in a vacuum - that's how you get the moisture out of the system, it boils and comes out as a gas. With a lower vacuum, the boiling point of water is higher, so there's no guarantee you can get ALL the water out of the system, which is essential.

Dale

BlueRex

Dale, the price of R12 varies by region. I've been quoted at about ~$70 a pound over here in CA. Since the production was halted at the end of 1995 the prices are only going to go up which is why the conversion kits are so popular. Any idea how many pounds are required to fill the a/c system?

Any comment on my previous question about the lack of performance from r134a in an r12 system being related to the compressor design?

DamonB

It's a combination of things. In a nutshell 134a is less efficient so cars designed for it have larger evaporators and condensors. A car originally designed to use R12 has evaporators and condensors that are not optimized (too small) for 134a and thus the a/c becomes "handicapped" when you convert an R12 system to 134a.

The other big bug-a-boo is that 134a runs hotter. If you merely charge an R12 system with the same amount of 134a your pressures will end up too high and the compressor life will be drastically shortened. You have to use less 134a to keep the system pressures in check. In the end it's a double whammy: The 134a is less efficient and you have to use less of it. I never charge the a/c without a manifold gauge set so I can monitor the system and be sure everything is within safe parameters.

dgeesaman

iTrader: (7)

There is a huge difference between systems designed for propane, and putting propane in an AC system. Propane fuel tanks are designed in many cases to withstand an 80mph crash into a solid concrete wall. Yes, we have flammable fuel lines in our cars too, but they are away from heat, crumple zones, and other nasties. IIRC the A/C lines are all over, and they're aluminum.

Dave

BlueRex

Thanks for the info DamonB.

In you previous post you said that you converted your car to r134a. Any idea how the conversion kit helps opposed to just putting r134a in an r12 system? IIRC all I saw in one of those kits were some new fittings and r134a refrigerant.

DaleClark

iTrader: (55)

The car only needs like a pound and a half of freon, BTW. It will be more or less depending on the region, but it should still be reasonable.

The proper way to do a 134a conversion is a little time consuming. The oil in the system should be drained and replaced with 134a compatible oil, and the O-rings should be replaced with 134a compatible O-rings. The system then needs a hard vacuum and a proper charge of 134a - Damon's right, you have to run less pressure with 134a to keep the head pressure at the compressor in check.

134a works great in a system it was designed for. It would be nice if there was a way to run 134a and have the same cooling you get with R12. For some people up north, 134a might be just fine. For Florida's heat and humidity, it isn't doing the job - car takes longer to get cool, and you end up running the system on full-blast more of the time.

I can't stress enough how pleased I've been with the AC in my car - not only does it blow ice cold, but it makes little to no difference in how the car runs, unlike my old FC 'vert that felt like I tossed out an anchor with the AC on.

Dale

mad_7tist

there is no such thing as an r-134 o-ring. when you retrofit replace the ones you remove and any that were leaking.