Automotive Air Conditioning Information Forum

Hello everyone. I am hoping to get some help diagnosing some issues with my 2014 Honda Civic Si Sedan.

Original Symptoms:

No cold air, pressure readings spiking on the high side, 250-300 psi, would spike up quick. When that happened pressure would go almost to vacuum on the low side. 2 -5 psi.

After some reading and watching a ton of videos, I convinced myself that it had to be the expansion valve that was malfunctioning. Had a friend with a shop recover the refrigerant for me and I went ahead and replaced the expansion valve.

While I rebuilt the inside of the car, I had a vacuum pump running for about an hour on the system. Then I kept it closed for about another hour and vacuum pressure held. I ended up putting two 12oz cans of r134a and I thought everything looked good. My pressure reading at idle were, 40 psi on the low side, 164 on the high side. Outside temps were mid 80s and a quick test drive made made it seem everything was working fine. Nice and cold ac.

Current issues:

Day after I thought it was fixed, on my commute home, about 95 degrees, the system started venting refrigerant. It did this a couple of times and once again I am with hot air. The system as it currently stands, readings are from yesterday afternoon, about 93 degrees out, car parked in the garage after getting home from work. (Read, car is hot, about a 45 mile, hour 15 min. Commute in Texas heat)

Stabilized pressures before restarting: 105 psi

Stabilized pressure after ac running at idle for 10 mins: 53 psi on low side, 146 on the high side.

Accelerating engine to 1600 rpm: 9psi low side, 120 psi on the high side.

I took the rpm to 2k and low side went 0, and high side crept down a little. Didn't really let it stabilize so no good reading there.


I am a bit at a loss as to what is going on. The best I can figure is that either my drier or condenser are clogged. What do you guys think? Ac also seems to work fine on my morning commute, but I get in really early when the temps are still in the 80s.

Sorry for the wall of words and thanks in advance for those that stuck around and read all of it. Let me know if y'all have any questions.

Other than what you described, had any work ever been done to the system before that?
Has a comp ever grenaded? If so, was the condenser replaced at the same time as the comp?
Almost seems like some kind of debris is in the system and making its way to the OT. When you replaced the OT (or was this a TXV system?) did you check the screen?
If you have a drier (and not an accumulator) the dessicant beads could be getting loose and traveling around the system.
How did you determine the 24 oz charge? was that what the underhood sticker said?
Can we assume your vacuum pump is driven by an electric motor and not compressed air?
Other consultants will be by to verify what the charge level should be

I don't believe any previous work had been done. I bought the car with 50k miles on it. No wrecks on the Carfax, all equipment looks oem original.

This system has an expansion valve, bolts directly to the evaporator assembly tubes, first thing on the inside of the car. No filter screen that I saw.

For the charge I went off of a post on a 9th gen civic forum, I should have looked up the FSM, but didn't.

I believe it is a drier, that's what come up when I look up parts for the car.

The vacuum pump is indeed an electric motor run unit.

Let me know if I missed any answers. Thank you!

You might have overcharged the system quite a bit after you replaced the TXV. Do you have an under-hood decal that shows the A/C specs? I ask because the specs that I have for your car list 15 ounces net weight of R-134a. So unless the decal says otherwise, the system was overcharged by roughly 9 ounces, which is why the PRV, a high-pressure safety device, vented refrigerant. I say "roughly 9 ounces" because a small-capacity system, such as this car has, must have a precise charge weighed-in for it to operate correctly.

When you replaced the TXV, did you find any desiccant beads in it?

You are absolutely correct. The underhood sticker says 15oz. I can't believe I didn't see that.

I didn't find any beads when replacing the expansion valve.

06Speed6 wrote: ↑Tue Jun 07, 2022 3:26 pm I didn't find any beads when replacing the expansion valve.

That's good. But since you had the system open to replace the TXV, I'd replace the desiccant anyway. I believe your car has a receiver/dryer cylinder that's integral with the condenser instead of a separate R/D. Kits are available from this site's sponsor that contain a new desiccant bag, a plug for the end of the cylinder, and a few o-rings.