AC compressor pressure relief valve Qs

[bogle]

I finally got around to replacing my ac compressor in my 91. Well, that is, I got the compressor out of the car.

For some context, I had the car converted to r134a by a shop, but they didn’t tighten one of the fittings all the way. I took it back, they tightened the fitting and they recharged with another round of R134a, then they ran it for a while. But then when I went to pick it up, they had it on the lift and the compressor was all covered in oil.

When I finally got the compressor out of the car, it seemed pretty clear that the leakage was from the pressure relief valve. You can see here it is extremely green inside of the valve opening.

My thought was to just replace the valve as a precautionary measure. But it’s a discontinued part for the 91 and 92 cars. I have the updated part from the later cars, but the threads are much coarser and it doesn’t fit.

Anyone know if these valves go bad? It’s possible the valve is fine and something else caused the high pressure, triggering the release valve. E.g bad compressor? an overcharge? or maybe a clogged condenser or something (I flushed them both tho)?

I read on another forum that you should replace them after they trip. Is that true?

I have a couple options

1. Run the old valve and hope for the best. If it is bad, I have to tear the whole thing apart again.
2. Buy a brand new flange connector “suction service” thing from Honda for the R134A cars (38838-PR7-A01)
3. Find a used flange from a prime member (omg if you have one from a 93+ car please let me know)

I’m leaning toward option 2 for safety, but it puts me out another week.

Anyone know the risk that the old one is bad? Would you replace it? Any tests I can do? The service manual only has instructions to remove / install it.

 

[drew]

If it is leaking, you gotta replace it (also verify your system pressures are going to the moon).

FYI, the compressor is a NipponDenso (ND) and Honda just OEM's it without any value add.

You DO NOT have to get the parts or the compressor from Honda and I just recommend to just find a genuine ND source. Many tens of millions of units out there and parts are everywhere and easy to get.

The pressure relief valve is specified by thread type....so get one that suits.

If you DO replace the entire compressor, I recommend the ND new or "10PA20C" Legend version as the displacement is higher than "10PA15C " in the same casing and tends to be a lot easier to get (The 15 was also used in the Integra, which also works, but has less displacement). Stay away from non-ND rebuilds or knock offs (ie Four Seasons, etc...). Do not turn in your OEM compressor, keep it for a future rebuild with OEM parts...they just don't make them like they used to. (displacement numbers from memory, you get the idea).

 

[bogle]

Thanks, yeah I have a new Denso compressor. It's a 471-1424 (the R12 one and I replaced the oil with ester). I'll be replacing the drier and compressor, and I flushed the condensers and the lines.

I went to the hardware store to work out threads on each of the valves:

* 91-92 R12 - 3/8"-24
* 93+ R134a - M10x1.5

I cant find a denso relief valve that is clearly 3/8-24 threads and not for R12. Generally info is super limited or conflicting for aftermarket valves out there. The four seasons 35762 looks like an option: https://www.rockauto.com/en/moreinfo.php?pk=7933300&jsn=3, but some places say it's only for R12. i assume because of the pressures.

In my research on this today, it looks like some people with conversions have these issues with the pressure valves as R134a systems operate at higher pressures than R12, so the relief valve should be changed to an R134a part. But it seems like other folks here use the old valve in R134a conversions with no issue....

Napa sells a conversion valve (TEM 209583), that seems like it has 3/8-24. threads based on this pdf. But is it a captive o-ring or not?

FWIW, this denso valve looks exactly like the $75 Honda part for the 93+ cars. $7 part is better than $75, eh?

I dunno, I think I might just pay the $200 for the brand new manifold flange + installed valve to know it all fits and works at the correct pressures...

 

[drew]

The NAPA part looks most excellent if you are concerned about the difference in operating pressure between R12 and R134a.
https://www.engineeringtoolbox.com/refrigerant-temperature-pressure-chart-d_1683.html (isn't much difference, but take a look).

The Honda factory conversion kit doesn't have a pressure relief valve included AFAIK. I don't even change out the o-rings unless there is a problem.

While I have not done it for this purpose, but you should be able to mix and match parts on the ND compressors to suit your needs...if you want a metric thread on your compressor manifold, get one...if it fits: it ships.

We're not launching rockets here, pretty low cost for failure here.

meanwhile, amayama has your part
https://www.amayama.com/en/part/honda/38838pr7a01

 

[bogle]

Lol, noted, not rocket surgery. I’ve never overhauled an AC system before. I just want to make sure I don’t have to pull the dumb compressor again in a month because of some little part.

I bought all the Honda parts for the top of the compressor, then I guess they were back ordered, and my order was canceled. So I ordered the Napa part, and will be able to pick it up tomorrow or Saturday.

For some reason I thought the pressures were way higher with R134a, I guess not.

Yeah i saw amayama had the original. I love buying from them but the shipping cost and lead times are a killer for one off things. The car is in the air and I was hoping to have it done like today, but this valve was a stick in my spokes. The next best thing was by next weekend, so amayama not an option in this case.

Hopefully the Napa part is The Answer and I can get the car off the lift soon.

 

[bogle]

For posterity’s sake, the Napa part will not work. It has a captive o-ring which will not seal in this situation. The housing has a recess for the o ring, so the valve itself cannot also have a recess for the o ring. I picked it up, looked at it and immediately returned it

Not sure what I’m going to do yet…

 

[ralph cerbone]

pressure relief valve

honda had problems with compressor relays sticking i believe on odyssey, caused the relief valve to unseat . not saying this is your problem just be aware of it . The contacs in the relay welded together , dealt with this twice

 

[bogle]

honda had problems with compressor relays sticking i believe on odyssey, caused the relief valve to unseat . not saying this is your problem just be aware of it . The contacs in the relay welded together , dealt with this twice

Thanks! Good to know. If it seems high, I’ll swap the horn relay around as it’s the same one. Ill order a few in my next amayama order too

 

[RYU]

[MENTION=5430]drew[/MENTION] might you know the part number for the "19 Legend" version? That's interesting info.
I might look into using the bigger unit as you mentioned. Much thanks

If it is leaking, you gotta replace it (also verify your system pressures are going to the moon).

FYI, the compressor is a NipponDenso (ND) and Honda just OEM's it without any value add.

You DO NOT have to get the parts or the compressor from Honda and I just recommend to just find a genuine ND source. Many tens of millions of units out there and parts are everywhere and easy to get.

The pressure relief valve is specified by thread type....so get one that suits.

If you DO replace the entire compressor, I recommend the ND new or "19" Legend version as the displacement is higher than "17" in the same casing and tends to be a lot easier to get (The 15 was used in the Integra, which also works, but has less displacement). Stay away from non-ND rebuilds or knock offs (ie Four Seasons, etc...). Do not turn in your OEM compressor, keep it for a future rebuild with OEM parts...they just don't make them like they used to. (displacement numbers from memory, you get the idea).

 

[drew]

10PA20C = Legend
10PA15C = NSX

The basic compressor swaps over without issue.

Do verify if the manifold needs to be migrated over from the 15 to the 20 (hazy memory believes it should be a drop in).

 

[RYU]

Much thanks [MENTION=5430]drew[/MENTION]

 

[99 rs]

I didn't want to start a new thread about an AC leak as this thread already comes up through the Search menu.

I have my engine out of my car but did the AC compressor unbolt "trick" to not have to depressure the system. I ziptied it to some undercarriage stuff but the compressor is basically sitting face down or leaning towards the pulley side. I looked under there today (last time I looked was October) and there is a drip from behind the pulley. Does anyone know if there is a non-pressurized oil level in the compressor itself? Or did my compressor spring a leak? The fluid is distinctively green. I have never had an issue before with the AC system and it worked in fall when I was taking the engine out. Car is a 2005 6MT. Only thing I can think of is that we had a particularly harsh winter this year with temps near -40. So with the compressor face down maybe the seal shrunk enough to let some fluid by????