2007 Honda CRV Low Pressures

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Pongolo
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2007 Honda CRV Low Pressures

Postby Pongolo » Sun Jun 14, 2020 9:01 pm

Hello,

I replaced all components in the AC system of my 2007 CRV three years ago and it never seemed to run right but it cooled ok at 58F. I replaced the refrigerant twice at that time thinking i had done the recharge incorrectly but still got the same cooling temp with the low side around 38 psi and the high side around 210 psi. I left the system as it was since it was cooler than before.

The AC started blowing hot air recently ​​​​​and I evacuated the system for 30 mins and let it sit for 30 mins at 30 in-Hg without any leaks detected. I recharged the system with 16 ounces of refrigerant per the spec and I'm back at about 58F out the vent with a low side of 38 psi and a high side of about 212 psi with an ambient temp of 85F. I noticed that the condenser fan wasn't running and replaced it. Now the pressures are about 33 psi on the low side and 155 psi on the low side with the air not feeling much cooler than about 60F. These latest numbers seem to low to me, especially the high side.

I'm pretty sure I should be seeing cooler air out of the vents, possibly in the low to mid 40F's but am unsure of how to achieve that. Could it be that the compressor I replaced never worked right out of the box? Could the orifice/metering valve be the wrong one?

Appreciate any help!

Thanks
Dougflas
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Re: 2007 Honda CRV Low Pressures

Postby Dougflas » Mon Jun 15, 2020 5:05 am

You could be having a reheat problem where the air inside is leaking and getting reheated by the heater core. 155 on he low side I probably a mistyped reading. Your new compressor could be bad but I do not think so.
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JohnHere
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Re: 2007 Honda CRV Low Pressures

Postby JohnHere » Mon Jun 15, 2020 7:56 am

Even at 38 PSI on the low side, you should be seeing vent temps lower than 58 to 60 degrees. So I agree that heated air is probably mixing in someplace.

Another question comes to mind. When you replaced all the components, how did you handle the oil--that is, what did you put in and how much?
Al9
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Re: 2007 Honda CRV Low Pressures

Postby Al9 » Mon Jun 15, 2020 8:33 am

JohnHere wrote:that is, what did you put in and how much?

And, most importantly, did you flush everything thoroughly enough?
Pongolo
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Re: 2007 Honda CRV Low Pressures

Postby Pongolo » Mon Jun 15, 2020 10:22 am

When I replaced everything I took all lines out of the car and flushed them completely. At the time, I replaced the evaporator, metering valve, condenser, drier, and compressor.

As for the oil, I added PAG46 oil to the evaporator, compressor, and condenser making sure to not exceed the total amount required per the service manual.

Also, I checked the blend door and it seems to be operating properly (closes all the way in the max cold setting) but I have not taken it out to physically check the mechanism.

The plot below is from the service manual and shows how the different values compare (33 psi on low side, 150 psi on high side, ambient temp of 85°F, and a vent temp of about 60°F).

Image
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JohnHere
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Re: 2007 Honda CRV Low Pressures

Postby JohnHere » Fri Jun 19, 2020 2:11 pm

Unless the under-hood sticker specifies 16 ounces of refrigerant, my references list 18.0 ounces of R-134a. So it might be undercharged by a couple of ounces, which is significant.

When adding the oil, was the system completely empty of oil, including the new compressor? The specification is only 4.5 ounces in total, a very small amount. If the compressor contained oil from the factory and wasn't drained before adding more, the system could be overcharged with oil.

I think the plot is incorrect. With a low side of 33 PSI and a high side of 150 PSI (which is rather low) at 85 degrees ambient, the vent temps generally should be around the mid 40's, not 60 degrees.
Pongolo
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Re: 2007 Honda CRV Low Pressures

Postby Pongolo » Fri Jun 19, 2020 3:13 pm

Thanks for the info!

The replacement was done three years ago and I want to say I drained the oil in the compressor and made sure to stay under the oil requirement. However, if there's too much oil in the system, is there a way to drain it out without taking the entire system apart so I can put in the right amount? I'm assuming no but want to verify.

Here's the sticker under the hood:
Image
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JohnHere
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Re: 2007 Honda CRV Low Pressures

Postby JohnHere » Sat Jun 20, 2020 8:00 am

Okay, good...you're within the spec for the refrigerant charge.

Unfortunately, there's no way to gauge how much oil the system contains now. The only way to know for sure is to disassemble everything, flush all the flushable components, drain the compressor, and refill it to spec.

Re-reading the thread, it sounds like you're close on the oil amount, though, assuming you put in 4.5 ounces three years ago. From here, the compressor sounds like it's working fine as well.

It could be that the TXV is acting up. When you replaced it, did you install an OEM unit or aftermarket? I've discovered that some aftermarket TXVs can be erratic. I found that to be the case in one of my own cars.
Pongolo
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Re: 2007 Honda CRV Low Pressures

Postby Pongolo » Sat Jun 20, 2020 3:23 pm

The TXV was an after market item, not OEM and since I replaced everything, I've always wondered if it was in fact the right one.

I'm not getting any complaints on the A/C for now but will plan on taking everything apart again when it starts acting up and change the TXV with an OEM one at that time.

Thanks for your help.
Al9
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Re: 2007 Honda CRV Low Pressures

Postby Al9 » Sun Jun 21, 2020 3:21 am

That car has a cross charged TXV (4seasons listing shows negative s/h).

Such a TXV restricts the refrigerant flow and works together with the compressor to bring suction pressure down until a certain suction pressure value is achieved (positive s/h zone), then it forces itself to stay open a little (negative s/h zone) instead of closing fully. In particular, scroll compressors benefit from such a TXV operation since the low/zero evaporator superheat keeps discharge temperatures in check.

Aftermarket producers could possibly use a wrong (i.e. not so fine-tuned as OEM/Denso one) sensing element charge in order to bring costs down, resulting in erratic operation.

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