I finally got my AC system leak free and holding vacuum, then and added about 19oz of R12 to it. Unfortunately I am seeing two possibly related issues. First my compressor will not kick on unless I manually give it 12v. The button in the dash is not kicking it on. Second, my high pressure reading does not seem right. When charging initially, it seemed to get stuck around 100psi even as the low side was continuing to suck in refrigerant. I added R12 by weight until I got to the point where I was concerned with the compressor not kicking on by itself and figured something must be wrong. Low pressure is showing between 36 and 43psi when the compressor is engaged.

I let the car sit for a few hours and the low and high stabilized around 80psi. I started the car again and manually engaged the compressor, and the high pressure gauge never moved, it sat right at 80psi without budging. This is making me think I have a clog in the system somewhere before the high pressure port, and since the compressor won't kick on, possibly a clog before the high pressure switch too? I think this means I have a clog somewhere in the condenser or dryer or hoses in between? When charging initially the car briefly blew cool air but not cold, and was warm after that.

I do have a PowerFC but with the weird high side readings I don't think I am experiencing the weird PowerFC AC ground issue. A few years ago I was able to charge the car with es12a without compressor problems so unless something changed I don't think this is an ECM issue

Any thoughts on what I should do next? I live in Texas now and not having AC has been a real pain

Initial charge video:
https://youtube.com/shorts/PTxgvT22vkA?feature=share

Later startup:
https://youtube.com/shorts/7aWDuiVXubw?feature=share

 

Haven't watched the videos yet, but this all looks potentially like a bad expansion valve.

When charging initially with the car off, both high and low sides should have the same reading. They should only differ when the compressor is running - that will compress the refrigerant and bring up the high side and bring down the low side.

You may have an issue with the PFC not kicking the AC on, but I think typically it's only on lower speeds, on speed 4 it normally works. You may have to do some troubleshooting to see electrically if there's an issue. The wire to turn the compressor on basically goes through the AC button on the dash, through the ECU, through the low pressure switch, then to the compressor. Study the wiring diagram for more info/details. It's easy to test each component with a meter to see if one is preventing things from happening. Oh, there is also the temp sensor in the evaporator box that will disengage the compressor when it gets too cold to prevent it from freezing up.

I typically pull to a hard vacuum 30" for a good half hour or more, drop in a can to start filling the system, then when the system won't take any more statically then start the car and use the compressor to draw it in. That first bit should be enough to cycle the compressor.

Dale

 

I can definitely do some electrical troubleshooting, but even so if I manually kick-start the compressor by giving it 12v I was not seeing the high side pressure change. Could a bad expansion valve cause that? Since the expansion valve is past the high side port in the system I assumed a bad expansion valve would still give me some movement on the high side gauge but maybe I am wrong. I am definitely not an expert here

 

OK, here's some of the idea of things -

The compressor is compressing the refrigerant in the system and pushing it towards the expansion valve. That valve is a small "spray nozzle", like the tip on a a pressure washer. Whenever you go from high pressure to low pressure you make things cold so that change through the expansion valve is what makes the AC cold.

If it's bad it could be wide open and not "spraying" per se, then you would have no change in pressure.

The shop manual has AC troubleshooting somewhere in it, it will show what pressures you are seeing and what to look at.

I know you fixed some lines too - any possibility somehow the lines got mixed up so the compressor is basically running backwards?

Dale

 

As I mentioned in your other A/C thread, air/moisture in the system from not bleeding out the yellow charging hose could be causing such symptoms. The moisture laden air freezes up and can tend to clog up things, especially at the expansion valve or dryer. Also IIRC, the high side pressure service fitting on the stock FD is plumbed in after the dryer, so if your dryer is frozen/clogged, you would expect to see a low/unchanging high side pressure, but if you had a service fitting on the high side line before the dryer, it would likely read sky high. This might also explain why your compressor is cutting itself off - the binary pressure switch opens the circuit if the pressure is either too low OR too high - a dead-ended compressor would quickly trigger the high pressure cut off.

Did you also replace the dryer with a new one when you last had it open? BTW, don't know if this applies to you but you should never use a used dryer, or even a new one if it's been stored with its ports open to the atmosphere for any lengthy period of time - the caps that are on a new dryer are there for a reason. The desiccant inside the new dryer will just suck up moisture from the air and ruin it if it's left uncapped for too long.

 

I got it all figured out and have cold AC now! It was a couple of rookie mistakes: it was just a bad compressor fuse, and a poorly fitting high-pressure quick disconnect. Turns out my high side pressure is fine but the connector wasn't fully seating.

I started going through the electrical troubleshooting in Section G-22 of the body electrical manual, and realized in step 5 that the AC relay under the hood had no power. That little 15amp fuse in the engine bay was blown! I can't believe I didn't think to check it sooner.

I also noticed that while my gauges read 75 and 80psi low and high this morning, by evening they were back to 80 and 88, same as yesterday evening. I forgot that the morning being 20º cooler outside would mess with the system pressure. Thankfully this means I have no evidence of a leak after 48 hours since it's right back where it started.

I was perplexed because the service manual lists many combinations of low and high pressure readings with steps to follow to address them, but my combination of a correct low pressure and low-ish, stuck high pressure didn't match any of Mazda's scenarios. Once I pushed my thumb down on the high pressure quick disconnect, the gauge shot up closer to 200psi immediately

AC is blowing ice cold now just in time for the Texas summer. Oh, and I did use a new dryer. Since this is a MANA car I had a local 'vintage' AC shop cut and weld in lines for a Subaru dryer which they identified would fit well in the factory location.

Thanks for all the help

 

Fantastic! Thanks for posting the result!

Dale

 

Caught this thread, I cannot find a new drier with the tubes, are they available?
Mine was switched from oem -> vmount configuration back to oem.
I fear it might have micro leaks.
The AC worked last summer/fall, but now this spring it not as cold.

 

If you have a Denso system driers are readily available everywhere. MANA is not, you will need to splice in another dryer like I did or look into using an RX8 condenser with an integrated dryer (I think there are write-ups for doing this with a VMount). Definitely start by identifying the source of the leak before ripping anything apart though

 

How to tell the difference between Denso and Mana?
I was going to take it to a AC shop and have them check for leaks but I think its a very small leak so I am not sure how they would find it.

I found the drier, but its the tubes I to the condenser that would have a crack after being bent up so muck.
Those are probably not easy to find, right?

Worst case to replace the condenser with RX8 condenser/drier, I found JP3 motosports has the mounting brackets, but they tell me I need new lines and those are $750

Found a post on the forum about how to use the rx8 condenser does sound quit so easy unless you know how to weld.

 

@Pete_89T2 I'm having a similar issue to the OP, but your comment here is pertinent to me, because I did not purge the yellow charge hose before starting to fill my system (rookie mistake, it was on one of the how to videos I watched, but not the other...which of course was the one I was watching again while filling). Curious if the issue you are describing could persist even after leaving everything sit overnight?

For reference, I'm doing the JP3 conversion with all new UAC components. I vacuumed down the system, it held vacuum overnight, so I started to fill the system. Everything was going great. The compressor kicked on, the vents were blowing cold....then, about 3/4 through my first can of 134a, I noticed the low side pressure way up. I looked at the compressor, and it looked like the clutch was trying to engage sporadically, but then after a minute or two, stopped trying all together. I left everything hooked up, and closed off the system and let it sit as I was troubleshooting. I checked the fuse in the car (good) and I swapped out the AC relay for a brand new Mazda unit. I tried again with the new relay, and the compressor never tried to kick on.

I'm going to try and put 12v to the compressor and make sure that it is still working, but if it is, should I have the system evacuated and replace the desiccant in the dryer and try to vacuum the system again to start over?

Also, the vacuum pump I rented only ever got the system down to -21 in/Hg on the gauge, where all the videos I watched, everyone was able to get the system down to ~-30. Could this also be part of my issue?
Thanks

 

^That certainly could be the issue - you really need to pull a strong 29~30 in/Hg vacuum to get all the moisture out of the closed system. If your vacuum pump was only able to pull down to ~25, it means one of two things (1) Crappy rented vacuum pump, or (2) If it pulled down to ~25 but held that vacuum overnight, you might still have a very small leak in the system - testing for leaks with vacuum is OK, but testing with pressure is the only way to find the tiny ones.

First thing I'd try is doing the evacuation again with a better pump - get it down to 29~30 in/HG and see if it holds overnight. If it holds, go ahead & charge the system with R134. If it doesn't hold, you can try hunting for leaks by charging with a can of computer duster gas (HFC152a), and hunt for the leak with one of those cheap Harbor Freight electronic leak sniffers - they actually work well when used properly!

 

I wanted to add to this thread; it might be obvious to most but don't shake the can or tip it upside down to "charge" the system faster. It will only introduce liquid into the system; you'll get weird symptoms and can ruin the compressor. It takes about 20-30 minutes for a 17 oz can to empty. You can speed up the process by heating the can by putting it closer to the exhaust or using a heat gun but please be cautious.

 

^Great points, and all very true, but one caveat to add:

If you're starting out with a completely evacuated system, in vacuum and the gauge set hooked up, and you KNOW that your system capacity is more than one can (i.e. > the 12oz standard can capacity of R134a) of refrigerant to charge, you can safely speed up the process by liquid charging that 1st can. Here's how to do it:

1. Engine NOT running, A/C OFF, Low & High side valves on the manifold both CLOSED, A/C system holding a strong vacuum.
2. Hook up the refrigerant can to your yellow hose, then bleed the yellow hose with the can upright (valve/fitting on top; bleeding the yellow hose as a gas)
3. Turn the can upside down, so the valve is on the bottom, and OPEN the Low side manifold valve.
4. At this point, most of the refrigerant in the can will be sucked into the system by the vacuum as a liquid. Since the engine & compressor isn't running, this won't hurt anything - the refrigerant introduced as a liquid to the closed system will phase change/expand into a gas, and in a fairly short time, you'll see both the Low & high gauges reading about the same pressures, say about 60~80ish psi (depends on ambient temps). When the pressures stop rising and Low/High sides are about equal, you're done - that's as much as it will pull in from liquid state. Some refrigerant will be left in the can; and the system is partially charged - enough for the compressor to run/cycle and complete charging as a gas (can upright)
5. CLOSE the Low side manifold gauge, and flip the can back to the upright position for normal gas charging.

Now you can start the car, run the A/C compressor and complete charging the normal way with the can upright.

 

Thanks Pete. I ended up renting a pump from another parts store, and got everything to hold vacuum. So I changed out the desiccant, vacuumed down the system for almost an hour, and purged the full line before opening the LS valve. Got everything to work as it should, and got my LS/HS pressures right with everything I've read.



It's crazy how much air comes out of that line when you purge it. No wonder things didn't work out the first time I did it. Thank you for the tips!