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Sgt Fox
Dec 21, 2004

It's the buzzer I love the most. Makes me feel alive. Makes the V8's dead.


Question with charging and pressures.

AC system was retrofitted with new compressor and expansion valve two or three years ago. I had a small leak on a fitting last year and my pressure was low this spring.

Evacuated the system, took a look at the leak joint, retightened and replaced o ring etc. Brought the system under vacuum for recharging and started to charge. Put in about 200g of refrigerant, started up the car, started to draw in more via low side. (Total system capacity is 750g). Instead of seeing the compressor cycle, the pressure just kept rising. Added in maybe another 125g of refrigerant before I turned it off. Pressure was up at 70-80psi low and 400+ high.

I think the 4seasons expansion valve might have failed. Low side pressures seemed way too high, you could see the high side effectively maxing out at 400+... Last year the expansion valve was making horrible noises at idle too.

Thoughts? I wouldn't expect a system which was just low on refrigerant to act this way.

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Sgt Fox
Dec 21, 2004

It's the buzzer I love the most. Makes me feel alive. Makes the V8's dead.


I can hear gurgling from the evaporator core/expansion valve so that is my first suspect. There is a chance I have too much oil in this system, due to conflicting information. I wonder if the oil may have clogged something.

Sgt Fox
Dec 21, 2004

It's the buzzer I love the most. Makes me feel alive. Makes the V8's dead.


At most I would have less than two ounces too much.

So I guess start disconnecting things and use some compressed air to check for obstructions?

Edit: took out the evap core and expansion valve unit. Air seems to flow freely through the core/valve. Put the airline on the suction line of the rest of the system, air flows freely through to the high side. Does not seem to be any clog.

Sgt Fox fucked around with this message at 03:06 on May 30, 2020

Sgt Fox
Dec 21, 2004

It's the buzzer I love the most. Makes me feel alive. Makes the V8's dead.


Motronic posted:

What's the pressure valve setup like in this? It's is low/high valve? Curious why it was still running at that high pressure.

And maybe you have WAY too much oil in there but haven't slugged the compressor. You said the system was retrofitted - what did that entail as far as line lengths/mix and match components and how was the system capacity derived after that?

It is a r134A system from a 95 mx3 retrofitted into a 323 chassis.

See:
https://forums.somethingawful.com/s...9#post494092169 -Hardlines
https://forums.somethingawful.com/s...9#post495302160 - Compressor and rubber lines made up to fit, no real change in length from the mx-3 system.

I am using:
-1995 MX-3 evaporator core (stock, did not replace)
-1994-1996 MX-3 expansion valve (4 seasons 39053)
-1995 MX-3 stock lines from compressor suction to receiver drier
-1992-1995 MX-3 receiver drier (4 seasons 33581)
-1992-1996 MX-3 condensor (APDI Pro 7014372)
-1992-1995 MX-3 compressor (4 seasons 57495)

System control is 95 MX-3 V6 logic pushbutton (not the i4 sliders)

Mazda 1995 MX-3 FSM: http://foxed.ca/323/fsm/1995%20US%20WSM.pdf
AC section is G, starts at pg 793 (AC section is G-50, pg 842)

On the stock hard lines, there is a pressure switch, it has a high and low cutout. High pressure cut is 430psi, which is what I saw happening.


Now, as for oil capacities, I had trouble interpreting the manual. This was listed:



So, since I was starting with a new, clean system I took that to mean:

1oz condenser
+ 2 oz evaporator core
+ 0.2 oz piping
+ 0.3 oz receiver drier
+ 5.92oz compressor
=9.42 oz

The 4 seasons compressor paperwork claimed different (I'll dig out the paperwork later, I can't remember if their online guide was different):
https://www.4s.com/media/5421/four-...acity-guide.pdf
"95-94 All Eng. - 26.50 Oz. R-134a; 6.25 Oz. PAG-100"

So, 6.25 oz.

I don't think I added the entire 9.42oz, I seem to remember splitting the difference around 8 oz. Mazda called for ATMOS GU10, which google claimed was PAG46. 4 seasons wanted PAG100.

One thing to note is that the system worked well for two summers. Last summer the expansion valve/expansion core area started making a hissing fluid sound at idle.

Sgt Fox
Dec 21, 2004

It's the buzzer I love the most. Makes me feel alive. Makes the V8's dead.


Motronic posted:

Wow, okay, nice documentation.

So most importantly, this was a working system. For a good long time. So I think we can safely say that the assumptions you made about oil quantity were good enough. Type, maybe not. But then again, you said you already pulled the expansion valve and it was clean. If you were having system damage I'd expect parts of the compressor to be in there.

So what's left? Maybe your receiver dryer? Without any other information or seeing it first hand I'd probably go with an expansion valve (since it was noisy) and a receiver dryer since you ought to be replacing that anyway after the system was opened.

When you took this all apart to blow air through it, I assume you didn't have anything nasty looking coming out? I'm having a real hard time coming up with how it could be the compressor since it is in fact creating a pressure differential.

I ordered the expansion valve on the weekend, didn't get a new receiver drier though... shoot. I've been careful of leaving the system open, after I emptied and blew the compressed air through (air compressor has a drier on it), I made sure to pull a good vacuum on the system for 30 min, so perhaps the drier isn't necessary? (If you think it is still, I'll place another order, might be best, I assume it traps some schmoo in the system as well? Plus I could reinstall with less oil?)

One thing to note, is that when the system was working well before, pressures on the high side were still higher than what Mazda stated in their manual. I would see 250-350 IIRC.

When I was blowing through the system, only clean oil/dye came out, no chunkies, no gel, nothing. Colour in the dye was as bright as new.

Thanks for your help so far!

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Sgt Fox
Dec 21, 2004

It's the buzzer I love the most. Makes me feel alive. Makes the V8's dead.


Yeah, fair, I shall order then.

I am pretty sure I got the correct oil. I don't really trust anything 4 seasons says. In this guide: https://www.extant.gr/datafiles//_M...essed_Part1.pdf
PAG 46 Mazda Compressors Atmos GU10
PAG 100 Mazda Compressors Atmos GU20

I also see listings for the Mazda oil part numbers:
A055-61-K39 ATMOS GU10 (PAG 46) refrigerant oil (60mL)
C003-61-K39 ATMOS GU10 (PAG 46) refrigerant oil (40mL)

So that seems to indicate PAG46=GU10

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