Doh, I knew you were going to say that.....

 

I realize this thread has some years on it, but I wanted to say thanks. As I am revamping my setup, I am doing a full A/C overhaul. Of course, the expansion valve was included.

Great write-up, and not too hard overall.

 

The expansion valve for the MANA systems is NLA from Mazda.

I dug around online and cross referenced various parts listings and came up with the following valves that *should* fit. The 5 digit numbers are all 4 Seasons part numbers.

1999 Miata -- 39169 (Superheat 1.5 degrees)

1997 Miata -- 39054 (Superheat 3 degrees)

1992 Infiniti Q45 -- 39273 (Superheat -.5 degrees)

2003 Mazda Protege -- 39055 (Superheat 5 degrees)

I want to run my evaporator as cold as possible without slugging the compressor, so I ordered the 1999 Miata valve since it has the lowest positive superheat. After comparing it to an original factory expansion valve off of a 1994 MANA car, it appears that it will fit. The only difference between it and the factory valve is that the equalizer tube on the Miata valve is a bit longer. I don't expect that difference to have any adverse impact in operation once installed.

I don't recommend the Q45 valve since it has a negative superheat which means it allows liquid refrigerant to leave the evaporator, and that could potentially slug the compressor.

 

I purchased the below. Direct fit..

1994 Mazda RX7 A/C Compressor from OnlineAcCompressors

 

Good find although the Miata valve I ordered was only $15.

 

Yeah, I wasn't happy on the price, but hopefully it should work well. Charging system in the next month or so.

 

As a note, those looking for the MANA drier, the link I posted above has it... I've had a hard time finding one.

Part# 60-30900

 

Nice. The picture they're showing for 60-30900 looks like a Denso drier.

Can you post pictures of the top of the one you recieved? I'd like to see if they corrected the way they machined the ports. The last batch of MANA driers the aftermarket made had the ports machined in such a way that the lines didn't seat correctly.

 

I'm on it. Yes, the pics from the site are off. Sales rep confirmed an attached bracket with rectangle top piece, like the MANA drier. I will confirm port fitment upon recieving it. Post back soon.

 

WRONG ONE....

The part number listed looks like the website picture. In turn, it is NOT the drier for the MANA system. Not even close.

I'll likely re-use my old one after I hit the system with a hard vacuum for about 10 hours. I'm using ES-12a refrigerant as well, so moisture shouldn't be an issue. My greatest concern was a possible blockage. Since driers are typically cheap and an easy replacement, I went looking. No luck yet.

I definitely want to thank the OP for taking the time on this write-up. It was very useful when I swapped my expansion valve and made the job so much easier!!

Cheers

 

Aw. No bueno.

Back to my previous plan of using the Nippondenso drier bracket to hold a universal drier with 3/8" o-ring fittings. I'm having some rubber hoses custom made to attach it to the rest of the system.

 

Be sure to use refrigerant specific O-rings, and use refrigerant specific NYLOG sealant/lubricant on all fittings, O-rings, and Schrader valves (yes there are A/C specific ones).

It is oil-based, and never hardens and does NOT contaminate your A/C system.

Prolongs their life, and a quality seal for a LONG time.

I've been using it for 5+ years now, and I don't get leaks anymore.

Both NAPA and my local A/C supply house had them in stock.

:-) neil

 

Did you ever charge your system? I tore mine down, flushed it, replaced the compressor, adapted a new drier using custom lines and threw the Miata valve in there, and it appears that it isn't feeding the evaporator as much refrigerant as it should. Not sure if it is debris that got caught in the valve, a bad valve, or if it won't work for this application.

BTW, I cross referenced the TXV that you linked to and it is UAC part number EX10033C which works out to 4 Seasons P/N 38663 which was used on these applications:
MAZDA 323 (94-91) MAZDA 626 (97-93) MAZDA MX-3 (93-92) MAZDA MX-6 (97-93) MAZDA PROTEGE (94-90)

 

Is flashgas shutting the valve down? If so, you may have to relocate the sense bulb to prevent this and allow the valve to open. I don't know what the superheat is supposed to be for the FD....but I think its probably designed as a starved evaporator (as there is no suction accumulator in the system).

 

After reading the Wikipedia article on flashgas, I don't think it is an issue. The liquid line is warm, but not hot, and the sightglass is clear. The only thing that comes to mind as a possible cause of flash gas would be the hoses I installed to hook up a different drier in lieu of the factory aluminum piping. It has a slightly increased inside diameter versus the factory stuff. But I would think I would see that in the sight-glass since the line leading to the drier also increased in diameter.

As far as the bulb goes, I was careful to orient it in the same way the factory did. I'm not seeing any evidence of the valve "hunting" on my gauges. What I am seeing at 1500 RPM is a low side pressure down around 15 PSI and a high side of 225 or so at 95 degree ambients, with no better than 65 degree air out of the vents. That doesn't jive with a 15 PSI low side. I didn't measure superheat, but the suction line is barely cool to the touch at the joint behind the airbox.

The TXV I installed is supposed to have a superheat value of 1.5 and a tonnage of 1.5, which matches Mazda's stated capacity for the system. Figured any valve would get me "in the ballpark" as long as the superheat was positive so I chose the one with the lowest superheat.

 

The evap is definitely starved, which is why the outlet temp doesn't correlate with the suction pressure. Unfortunately, my impression is the same as your conclusion: the pressures suggest to me that the expansion valve is closed or blocked; although I suppose it could be blocked upstream, but that is easily checked. I don't think your drier adaptation would have any effect on operation and shouldn't be a problem. If you can get to the control bulb, you might try heating it and see if anything changes.

I also would expect the valve you put in to work ok for the application; however, I'm sure I've seen a Mazda specification capacity of 2 tons for the system, iirc..

 

There were no cold spots on the condenser or any of the liquid lines, so I don't think there are any restrictions upstream of the TXV, unless there's another easy way to check that I'm not aware of.

Mazda lists a cooling capacity for the system in the 1993 Service Highlights manual of 3,900 kcal/hr which Google says is 15,466.1006 BTU/hr or 1.28 tons. I would assume there is a direct relationship between overall system capacity and valve tonnage, but I don't know for sure. If you've seen 2 tons somewhere I'd be curious to see that documentation. Maybe the MANA system has more cooling capacity? The specs I've seen indicate that it holds ~6 ounces more refrigerant....but they also indicate that the receiver drier for the MANA system is a greater volume.

The Nippondenso system uses a 1.5 ton valve with a superheat of 8. Not sure what sorts of conclusions I can draw from that for the MANA system.

If it really is a 2 ton valve then we're screwed. Everything I see that would fit mechanically is 1.5 tons.

 

Update: Finally got my system back together and recharged with a 4 Seasons 39054 expansion valve and it is cooling well. This valve is for a 94-97 Miata and 1999-2000 Protege.

I think the first expansion valve I tried, the 39169, was simply defective.

 

Dusting off an old thread.
I need to replace my expansion valve. Can you say how the 4 Seasons 39054 worked out long term for you? Thanks.