A/C Woes
09-23-17, 06:55 PM
#1
Recovering Miataholic
Thread Starter
A/C Woes
Our '94's engine was replaced, so of course the A/C system had to be refilled (with R12; car was built 11/93). The A/C had worked perfectly for 23 years. Paid $292 total for the refilling job; $231 of that was for the R-12 Freon. Unfortunately the pressure relief valve on the bottom of the A/C compressor opened during the engine break-in period, and all the Freon was vented. Our mechanic Yoshiya says he has heard that if the relief valve opens, it may need to be replaced or it may open again at lower pressure (design problem?). So to avoid that he will replace it and also the A/C pressure switch, which are low-cost items, somewhere around $15 and $35. But this means that the system has once again to be refilled.
Does anyone have any knowledge of this sort of A/C disaster happening on other RX-7s?
Does anyone have any knowledge of this sort of A/C disaster happening on other RX-7s?
09-23-17, 07:23 PM
#2
Mine blew the high pressure valve due to over charging the system. My AC guy filled 29oz of r12 in mine. When it blew, it dumped all the Freon in the matter of minutes.
from what I know. The pressure valves works 1 time and must be replaced. I replaced mine. I'm searching for a pressure switch too. If you get the info please share.
from what I know. The pressure valves works 1 time and must be replaced. I replaced mine. I'm searching for a pressure switch too. If you get the info please share.
09-23-17, 07:33 PM
#3
If the relief valve went, it will need to be replaced. There is a cap like foil that will burst and vent the system in the event it is over pressurised.
So, there are two potential causes:
1) The system was overfilled. This would allow a large amount of liquid refrigerant to hit the compressor at once.
2) The system was properly charged and something else caused it to over pressurize. So the fans failed to come on due to a faulty switch or other issue, and the high limit switch failed to cut the compressor off when the pressure was too high.
This however begs one real question:
Why did your mechanic empty the system to start with? It is not a necessary procedure to remove the engine. If you unbolt the compressor from the bracket, then you just leave the compressor in the bay attached to the lines and the system stays charged. It's a little bit of a pain when you drop the engine back in, but I did it with that and the PS pump done the same way and the transmission attached to the engine.
Vince
So, there are two potential causes:
1) The system was overfilled. This would allow a large amount of liquid refrigerant to hit the compressor at once.
2) The system was properly charged and something else caused it to over pressurize. So the fans failed to come on due to a faulty switch or other issue, and the high limit switch failed to cut the compressor off when the pressure was too high.
This however begs one real question:
Why did your mechanic empty the system to start with? It is not a necessary procedure to remove the engine. If you unbolt the compressor from the bracket, then you just leave the compressor in the bay attached to the lines and the system stays charged. It's a little bit of a pain when you drop the engine back in, but I did it with that and the PS pump done the same way and the transmission attached to the engine.
Vince
09-24-17, 01:52 AM
#5
When my a.c. guy added Freon. He didn't specifie how much he put in. He just said he followed the sticker on the hood. Which clearly says. 1lbs 4 some odd oz or 5. Later after I blew my ****. I asked him again he said a little under 2lb. 2lb is 32oz. Even if it's a little under. It's still way too much. He then said that it's an old car and over time the lines
stretch / expanses....yadi yada. I was pretty pissed to say the least. Be promise a free refill to what ever amount I say. So. Double check
stretch / expanses....yadi yada. I was pretty pissed to say the least. Be promise a free refill to what ever amount I say. So. Double check
09-25-17, 03:58 AM
#6
When my a.c. guy added Freon. He didn't specifie how much he put in. He just said he followed the sticker on the hood. Which clearly says. 1lbs 4 some odd oz or 5. Later after I blew my ****. I asked him again he said a little under 2lb. 2lb is 32oz. Even if it's a little under. It's still way too much. He then said that it's an old car and over time the lines
stretch / expanses....yadi yada. I was pretty pissed to say the least. Be promise a free refill to what ever amount I say. So. Double check
stretch / expanses....yadi yada. I was pretty pissed to say the least. Be promise a free refill to what ever amount I say. So. Double check
If your system (or hood for that matter) has been swapped out, then the system's capacity could change (or the sticker could be wrong); so there are possible explanations for an honest mistake.
Another thing to watch for is proper oil fill; these systems only hold a few ounces and it's very easy to overcharge them with oil when refrigerant oil is accidentally or arbitrarily added when the system or a component is serviced. Other culprits are clogged condensers, which would probably be associated with a prior compressor failure. A large amount of air trapped in the system prior to being charged with refrigerant (likely due to no or poor evacuation) can cause problems as can severely restricted airflow over the condenser. All of the foregoing conditions, alone or in combination, will raise discharge pressures (and temps) to dangerous levels that could precipitate a failure. Refrigerant overcharge can, of course, be a factor--but I would expect to see something else going on as well.
09-25-17, 06:21 AM
#7
One thing you should be aware of concerning FD a/c: many of you know that there are two different systems used depending upon the trim level your car has; one system is by Denso and the other known as MANA (I believe this is Mazda North America). The significance of this is that the two systems carry significantly different refrigerant capacities. The Denso system is smaller and in fact takes only 1lb 4oz; however, the MANA system takes 1lb 12.2oz according to my hood sticker. There may be service literature out there that states other capacities or is simply in error. Normally, when you charge an a/c unit, you're watching the low side pressure and would see a gross overcharge--not to mention that it wouldn't cool very well.
If your system (or hood for that matter) has been swapped out, then the system's capacity could change (or the sticker could be wrong); so there are possible explanations for an honest mistake.
Another thing to watch for is proper oil fill; these systems only hold a few ounces and it's very easy to overcharge them with oil when refrigerant oil is accidentally or arbitrarily added when the system or a component is serviced. Other culprits are clogged condensers, which would probably be associated with a prior compressor failure. A large amount of air trapped in the system prior to being charged with refrigerant (likely due to no or poor evacuation) can cause problems as can severely restricted airflow over the condenser. All of the foregoing conditions, alone or in combination, will raise discharge pressures (and temps) to dangerous levels that could precipitate a failure. Refrigerant overcharge can, of course, be a factor--but I would expect to see something else going on as well.
If your system (or hood for that matter) has been swapped out, then the system's capacity could change (or the sticker could be wrong); so there are possible explanations for an honest mistake.
Another thing to watch for is proper oil fill; these systems only hold a few ounces and it's very easy to overcharge them with oil when refrigerant oil is accidentally or arbitrarily added when the system or a component is serviced. Other culprits are clogged condensers, which would probably be associated with a prior compressor failure. A large amount of air trapped in the system prior to being charged with refrigerant (likely due to no or poor evacuation) can cause problems as can severely restricted airflow over the condenser. All of the foregoing conditions, alone or in combination, will raise discharge pressures (and temps) to dangerous levels that could precipitate a failure. Refrigerant overcharge can, of course, be a factor--but I would expect to see something else going on as well.
I've done all the o rings and o ring lubrication with mineral oil
but did not check the oil level. The compressor never came off due to me being lazy.
seems like it's not as simple as checking o rings, leakages, and proper working fan system.
when my a.c. system overheated and dumped the Freon, it was about 115f ambient temp. I'm just thinking it is too hot and the system simply can't handle it. Even with the fan on high .