2008 Civic EX. Low low side, high high side. Cycling too much

[somedude01]

2008 Civic EX Coupe

Hey there. I rebuilt the AC unit last May all except the evaporator and TXV because the compressor case was leaking. I put a genuine Denso compressor in it and new condenser. All new o-rings everywhere. Worked incredible but 2 weeks later the evaporator developed a leak that I could smell. I drove it for a few months, but I later put a UAC evaporator and genuine Denso TXV on it in September, and from there the A/C was never right. I let it go until the new hot season now. Weighed in a 16 ounce charge from a deep 2 hour+ vacuum.

Seems to cool great at an idle and when you start it from a cool garage, but you drive and it starts to cycle very often. It'll also cycle when heatsoaked on a hot day. I taped my gauges to the windshield and went for a drive. On a 90F humid day while cruising the low side will go down to 8psi for a few seconds and cycle off. It'll come back on after 5-10 seconds. The high side seems to be fine at around 200-225. This is repeatable for the entire drive.

20240531_132203 - frame at 0m14s.jpg (57.68 KiB) Viewed 2504 times

I set it to outside air and rolled the windows down and raised the idle. Low side this time was hanging out around 20-30 but the high side absolutely skyrocketed to 350-400. It never shut off while I did this for a minute, but I'm assuming it's hitting the high pressure cutoff on the hottest heatsoaked days because it does cycle off when I leave work until it cools down for a bit.

Am I correct in assuming a low low-side and high high-side and erratic cycling behavior will be a stuck closed or clogged TXV? It's a few hours up under the dash so I want to be sure lol.

Video of the AC running very well while we drove but the high side is climbing to 300 ish. The low side seems to hang out at around 16-18 psi: https://youtu.be/lMM0EqlMUAI

[tbirdtbird]

I am concerned for the txv.
You did not mention what you did about oil change.
Wait for another consultant to respond before you do anything

[Cusser]

Could your compressor clutch have too large of air gap, even though new?

[JohnHere]

When you replaced the evaporator and installed the new Denso TXV, the system was again opened to the atmosphere. Did you replace the receiver/dryer at that time?

[somedude01]

Because everything was new except evap and the lines were flushed out it got the exact amount minus the amount the evaporator holds. When I did the new evaporator I added what the factory service manual said when replacing the evaporator. I think I posted here asking for that advice because the compressor had an oil separator or something. In total I wound up with around 5 ounces of oil I think.

I checked the clutch gap before I installed it. It was in spec. Been burned too many times on this and it just takes a few minutes extra to look while it's out.

[somedude01]

When you replaced the evaporator and installed the new Denso TXV, the system was again opened to the atmosphere. Did you replace the receiver/dryer at that time?

No. It was taped off while I did the work. I wasn't going to do another new condenser since it's integrated and basically new.

[somedude01]

So I found someone with the same exact problem I'm having while shopping around. And apparently there's a different expansion valve for the coupe and the sedan. My crackpot theory is these aftermarket suppliers are calling the coupe and sedan valves the same and shipping the sedan part. Although my Denso part was specifically for the coupe and came from Rockauto. I don't want to waste my time again under the dash so I'm going to order a Genuine Honda TXV from the dealer and be done with it. I'll report back in a few weeks I suppose. I'm sure there may be others with this problem and this could help if it fixes it.

[JohnHere]

I've had similar problems in the past, but with aftermarket TXV's. After changing-out apparently defective parts several times—wasting time—I now stay with OEM TXV's, when available, and never had to replace any of them.

In your case, I can understand how a supplier could make that mistake: Both TXV's look the same, came from the same manufacturer, probably in similar looking boxes, but are calibrated differently. Key difference.

[Tim]

Depends on the after-market supplier. We show a different valve for each.

[somedude01]

The Genuine Honda expansion valve worked. I think I'm done with this rebuild once and for all. I reused the condenser and receiver drier again and charged 16 ounces.

I was getting 200 psi at an idle on a 94F day, 92F measured at the bumper. For some reason my gauges weren't reading the low side properly so I couldn't get a reading unless I was pushing down on the connector. It was hanging out in the 30-40 psi range.

I was seeing 48F at the center vent while idling and closer to 44F while driving. This was with the car closed up and on recirc since Florida's temperature and humidity is insane. I didn't tape the gauges to the car again but I did notice it's not short cycling on me at all anymore.