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Low low side, high high side

CyFi on Sun April 12, 2009 11:03 PM User is offline

Year: 1987
Make: Toyota
Model: Supra
Engine Size: 3.0
Refrigerant Type: R134a
Ambient Temp: 75-80
Pressure Low: Pressure High: 275

Hi, i converted my Supra a while ago and ever since i have had nothing but issues. I flushed everything out properly and charged everything properly. I replaced the TXV, Receiver dryer, fan clutch(OEM), and all the seals in the system. I charged it and used ester oil along with it.

In city driving i have problems with ac vent temps, but only when ambient temp is high (90+). With high ambient temps, the AC works well on the highway and gets down in the low 40's. But as i said on hot days in the city my vent temps are terrible in the upper 50's-60's.

I have a brand new OEM fan clutch that pulls plenty of air (fan shroud good). While idling in hot weather and high vent temps, i can mist the condenser with a hose and vent temps to not drop more than a couple of degrees if that, so i feel that airflow is not my problem.

I just hooked up my gauge set today after a long time and it was about 75 degrees out. Vent temps were great, 35-40 degrees. The gauge reading was around 25PSI and 225 PSI at idle, but at a high idle (1500-2000) low side dropped to about 10 or just below 10 psi, and high side went up to just over 275 psi, vent temps stayed cold.

I have no idea what is wrong with my system, i have taken it to my dealership and they recharged it again and there was no change in performance and they could not figure out what was wrong.
The only thing i can think of is a bad TXV. I used an aftermarket one and it fit very badly. Its orientation was 90 degrees different compared to OEM. I read everywhere about people having similar problems with fitment but everyone said it was ok/ normal. Here is what the new one looks like compared to how the old one fit.

Thanks for any help!

mk378 on Mon April 13, 2009 7:50 AM User is offline

Your TXV will not work properly installed like that. They have an in and out. In at the bottom and out at the side. Note the arrow molded into the old one. Your new one is plumbed backwards.

The ones (such as those) without a pressure sensing line work by sensing evaporator pressure at the "out" port. Installed backwards so high side pressure applied there all the time, the valve will stay at minimum opening. The only reason you're getting much cooling at all like that may be that the valve is also too large for your system.

The other vital thing about TXV replacement is to get the sensor bulb properly attached to the evaporator outlet line and insulated.

Edited: Mon April 13, 2009 at 8:52 AM by mk378

CyFi on Mon April 13, 2009 3:24 PM User is offline

OK so it looks like theres a little bit of hope then. The odd thing is that this TXV didnt have a flow arrow like the old one did, so i assumed it was ok, especially since the threads were as such that this is the only way it would fit. I will buy an OEM TXV and install it and go from there.

Also, the temperature sensing coil was properly mounted and insulated (not shown in picture)

Edited: Mon April 13, 2009 at 3:25 PM by CyFi

CyFi on Thu April 16, 2009 11:51 PM User is offline

Can anyone else confirm this? I looked in my school text book and it shows the inlet/outlet setup just like how my aftermarket one is. Inlet on the right, outlet on top. This means the OEM valve is opposite what my book says. Now i dont know what to think...

bohica2xo on Fri April 17, 2009 3:16 AM User is offline

Your first clue should be the huge valve with the adaptor screwed on it. Obviously not the right part - one size does NOT fit everything in refrigeration.

The site sponsor shows the correct TXV in stock HERE.


"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

NickD on Fri April 17, 2009 6:27 AM User is offline

Two small cans of R-12 is all you need for this car, with even a ounce or two left over. Is it really worth it to convert to R-134a?

CyFi on Fri April 17, 2009 12:44 PM User is offline

No, but its too late now, and now the question is, is it really worth it to do everything to convert back to r12

NickD on Fri April 17, 2009 2:09 PM User is offline

is it really worth it to do everything to convert back to r12

Since I own this one, afraid my answer to that question would be biased. Perhaps someone else less biased would give you an answer.

Does yours have the turbo? Another good reason to stick with R-12.

CyFi on Fri April 17, 2009 2:17 PM User is offline

not yet it doesnt, but soon it will. Im going to go over to az mobile air inc and get some price quotes. I was also having some cooling system issues running the AC though..

NickD on Sat April 18, 2009 7:43 AM User is offline

You already are experiencing problems with an R-134a conversion, just can't add a turbo to the 7MGE engine, the 7MGTE along with all that other stufff, cooling, IP, transmission, drive train, engine, exhaust is an entirely different car than the non turbo. Guys that tried just adding an aftermarket turbo blew up their engines in case you didn't know that.

CyFi on Sat April 18, 2009 3:16 PM User is offline

yes, i understand that, im in the process of rebuilding a full 7mgte im not planning on half assing anything here...

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