ericgrau

iTrader: (1)

My A/C has been weak but still functional for over a year. Should I recharge? Should I leak test? Should I vacuum it before recharging? All of these? 2 of these?

Here's a little background:
My A/C isn't cold enough. It's been cooling a little bit since I bouhgt it a year and a half ago: vents are 15 degrees colder than ambient. So I got some cans of Freeze 12 plus some Freeze 12 A/C oil. I called the mechanic I'm going to go to. He said that if it still cools a little I probably don't have a leak and should just recharge. He can also put in UV dye, leak test, fix minor leaks and vacuum for $89-$129 (depending on how bad the leaks are). I forget whether or not that includes a recharge, so it might be less since I'm doing the recharge myself.

I neglected to buy any Freeze 12 w/ UV dye and I don't want to put in R-134a w/ UV dye if I can avoid it. I do have a blacklight.

Also, I noticed that several minutes after I park after a long drive I get a buttload of water dripping down. As if my entire radiator just leaked out except it's A/C condensation not coolant. Do you think there might be some kind of restriction or broken freeze prevention?

RotaryResurrection

iTrader: (8)

For no more than it will cost, I would suggest replacing all the o-rings in the system before the recharge. You can get an oring kit with the other a/c stuff at autozone for less than 10 bucks.

As for the vacuum question, I'd like to know the answer to that as well. In the past I've always just charged the system up to pressure and hoped for the best.

ericgrau

iTrader: (1)

If I replace the o-rings won't I let air into the system? Then I'd definately need a vacuum to get out the air before I recharge.

How cold does your A/C get with just recharges? Have you checked it with an A/C thermometer? How long does a charge tend to last?

RoughRex

I just had my A/C done a week or so ago. Mine was completely empty of freon though. I replaced the receiver/drier and had the system evacuated and recharged at an A/C specialty shop. It took 28 oz of R12. My vent thermometer reads right at about 40 degrees most of the time. I've seen it get down to about 35 occassionally though.

RotaryResurrection

iTrader: (8)

Obviously, replacing the o-rings would let all the existing charge out. However, if you are saying that your current charge is low, where did all the other charge go? OUT THE O-RINGS. Just because the current charge is holding in the system at low pressure, does not mean the new charge will still hold in the system under higher pressure.

My a/c is the coldest of any rx7 I have ever been around, and I have been around a lot. I put in 2 cans of freeze 12 plus the oil charge after installing the a/c components. Vent temps are in the low 40's at idle and high 30's when driving.

ericgrau

iTrader: (1)

Wait, so you did that without vacuuming or you mean you vacuumed after installing the A/C components and you don't want to vacuum again?

And are there any other notable A/C components besides the o-rings? How much is a new receiver/dryer? How long does your system hold a charge?

I mean, we're talking around $100 for something I might not need. Or on the flipside possiblly paying an extra $20-$30 for the freeze 12 I leak out (on top of what I then discover I need to pay for anyway). Which brings another question. How would I then go about finding the leak if it only appears under full system pressure? R-134a w/ dye? Buying freeze 12 w/ UV AND more freeze 12 just to bring it up to full pressure again? Then vacuuming it all out to fix everything, then either buying more freeze 12 or somehow recovering what gets vacuumed out??

RoughRex

I didn't replace all the o-rings on mine... I knew I should since the A/c had been empty for years but I was feeling lazy. I only replaced the ones at the compressor and the ones at the receiver/drier. I don't remember exactly what I paid for the receiver/drier but I want to say it was $25 - $35.

ericgrau

iTrader: (1)

Hmmm, thanks very much. So if I ever do have the system depressurized I might as well replace the o-rings and receiver dryer while I'm at it. Are the o-rings really that much trouble to replace?

And I still don't know whether to get the system evacuated or not.... Dang it. I'm tempted to gamble on the ~$35/minimal-effort side (recharge only) b/c then either way I'll know for sure. I'll just be down $35.

RoughRex

I had mine evacuated just to be safe. I didn't know how long it had been empty or what may have been put into it. I've seen some of the handywork of the last twit that owned this car and I was not about to assume he didn't F it up somehow.

ericgrau

iTrader: (1)

Maybe I should flip a coin...

If I replace the o-rings is that sure to stop all the leaks? Or are there other spots that can leak too? Can't the metal tubing or fittings leak, for example?

RotaryResurrection

iTrader: (8)

At each fitting where each line connects to another, there is an o-ring. There are 9 or 10 total, I believe. The lines themselves can't leak unless they have been twisted or kinked.

I cannot tell you "how long the system holds charge" because I have only had the car running since March. Except for an overpressurizing incident I had due to insufficient fan cooling, mine seems to have held 100% charge thus far. OF course, with new orings I would expect nothing less. Old o-rings are like old valve stems on tires, they are a slow leak.

Here is what I would like to know regarding the vacuum process. Is it solely a method of removing old refrigerant and checking for leaks? OR does it allow you to fill the system with more refrigerant?

Vacuum is the partial or full absence of atmosphere in an enclosed area. Or, put another way, with respect to atmospheric pressure (what we regard as zero pressure) a vacuum is negative pressure.

IF air is filling the a/c system and you add refrigerant in, you can add X amount before it becomes full.

IF vacuum exists in the a/c system, then obviously less air is inside. Does this mean you can then fit more refrigerant into the same space (since there is no air)? More refrigerant should equal greater cooling capacity...or does it?

ericgrau

iTrader: (1)

Wait, so you didn't vacuum out the air before recharging?

Supposedly the A/C doesn't cool as well if there's air and/or moisture in there. I mean, it certainly doesn't, but if you didn't evacuate and still managed 40 degrees, maybe it isn't so bad?

Oh well, no more wasting time. Time to get to work. Going the cheap route for now...

ericgrau

iTrader: (1)

It's recharging rrrrealy slowly now. Did I somehow install the schrader valve wrong? I screwed it in on the side toward the outlet/me/not-the-AC-system. I made sure it could be pushed from my side, not the AC-system side. I then gently wrench tightened the adaptor onto the AC's low side inlet.

So I removed the (still half full) can of Freeze 12. I pushed on the valve with a pair of pliers, and sure enough it hissed and sprayed oil onto my pliers even before I pushed it all the way in. The rubber on the fill line seems to have chipped off on one side.

john ward

iTrader: (7)

for optimum performance the system should be put into a vacuum after evacuation. anytime the system is open [lines taken off] the receiver dryer should be replaced. if its humid out the dessicant in the dryer will not be at its potential. on the other hand it will work just fine if you just charge it but will not be as cold if there is moisture in the system.

ericgrau

iTrader: (1)

Oh well I just took it to a shop. Mechanic happened to comment that he wouldn't be using the fittings in my kit because they take forever. He said the expansion valve was clogged; I wasn't getting any low side pressure. He backflowed it, charged the system, then revved a little and got it to partly unclog, told me to come back for a new valve if it didn't clear up. It cleared up on the way home, immediately after a weee bit of acceleration on the freeway. My thermometer reads 40 at idle. A little less at speed.

RoninRX7

I just recharged my 90 vert last sunday and when i did it was blowing 28 degrees out of the vents! I didnt even think it could be that cold. It hasnt warmed at all, at least that i can notice. I guess its because it only has 62K OG miles on it, so everything is in top shape.

Its good to hear that you got the problems with yours sorted out. A recharge should last just as long as the first one did if it was done properly.

Brody8877

iTrader: (10)

I thin 88 FC uses R12, and im not sure do ppl recharge r12 anymore.

jackhild59

iTrader: (7)

Here is the reason(s) for evacuation. It removes contaminants-Moisture, old refrigerant(especially if someone else put in the wrong stuff-it happens) and air.

If you have an unknown blend of refrigerants, you will have a pretty good chance of poor performance. If you just add 134 to R12 system that still contains R12, you can actually have increased pressures compared to R134 alone.

If the system contains air either from the system being completely empty or more likely from poor charging procedures (you did flush that charging hose before you hooked it up, right?), you get extremely high pressures on the high side. Air does not condense. To keep from blowing up the system, you have to UNDERCHARGE! So, the answer is yes, you can get more refrigereant in if there is no air.

The moisture in the air also gives problems. The expansion valve blockage that ericgrau has is likely ice. As the refrigerant expands and cools, any water vapor is turned into ice inside the valve which eventually blocks it up, reducing cooling capacity.

Evacuation is just a good idea, unless you have a known system. And most of us do not have that.

jackhild59

iTrader: (7)

The original driers in our cars were meant for R12. The desiccants works fine for R134 containing refrigerants, but the BAG that holds the desiccants does not. If you have an original drier or an original Mazda sourced drier, it is possible for the bag to dissolve and release the dessicant into the system. It makes a mess right up in front of the expansion valve. I have personally seen this happen.

Pretty much all of the driers made now are compatible with both refrigerants, so if the drier says for R134a it is ok for R12 as well.

Actually, the most common point to leak is at the compressor shaft seal. I am told by A/C compressor engineers (yes, we have one of those in the family) that all compressors leak at the shaft seal to some degree. That is why you see so much oily residue on compressors. It is also why you need to occasionally run the compressor during the off season. Keeping the seals oiled helps reduce the seepage.

Second most common place to leak is at the service valves, especially if you have R134a conversion adaptors.

Very true.

Hope this helps.

stylEmon

iTrader: (2)

i charged the system after replacing all the o-rings, but the ac wont come on by itself. i have to jump the wire in order for the compressor to come on. I checked the relay, but I dont think thats the problem. also the efan comes on even if the ac is not on.

Anyone got any seggestions?

RotaryResurrection

iTrader: (8)

Bad pressure switch? Not enough charge?

stylEmon

iTrader: (2)

thanks, i think there may not hhave been enough charge...

Innovation

iTrader: (1)

Ignition switch. Bump it back a 1/4 turn after starting and see what happens.

ericgrau

iTrader: (1)

The mechanic vacuumed my system, etc. So it wasn't ice blocking the expansion valve. He said hopefully the fresh oil would help soften the crud up and hopefully the now full system wold help blow it out. If not, I would have needed to get it replaced. But my system got better on the way home from the mechanic, so that's all good now.

To anyone else wondering what to do with their A/C (like how I wondered before), I'd recommend just taking it to a shop the first time around. That is unless you deal with a lot of cars and want to buy the proper equipment (lots of $) and manual(s). Or unless your A/C is totally toast and you're replacing everything anyway. That way the shop can find any leaks, fix any problems and of course vacuum out the system. All dealt with, no worries, no hastle. It just turned out to be simpler. I mean, there's too much to learn and too much equipment to get for just for a one time need. Now that that's done, I plan on DIYing it. I'm gonna check my A/C from time to time and recharge it when the Haynes manual says to (being sure not to overcharge). I can get some refrigerant with dye and use my cheap blacklight light bulb to check for major leaks. Also the Haynes manual says to run the A/C for at least 10 minutes each month (even in the winter) to keep oil in the system. Otherwise your seals and what not can dry out and fail.

stylEmon

iTrader: (2)

so what all did they do, and how much did it cost?

I am having problems getting the AC to turn on by it's self. I have to jump it to make the compressor kick on.

I think it was because of a leak, that has been fixed but I havent re-charged the system yet.

My worry is that one of the other components is faulty (ie. the relay, the presuure switch, what ever else is on the circuit).

I may re-charge it, then just have a shop diagnos the system, and fix myself once I know exactly what it is.