Automotive Air Conditioning Information Forum (Archives)

Big Dawg on Mon July 04, 2011 8:50 PM

Year: 1990
Make: Nissan
Model: 300ZX
Engine Size: v6
Refrigerant Type: R134a
Ambient Temp: 90
Pressure Low: 35
Pressure High: 250
Country of Origin: United States

Checking my AC with my AC manifold gauges after my Z was retro fitted for R134a at a local AC shop shows 35psi low side and 250psi on the high side with engine running, doors closed, windows opened, box fan blowing and 90 degrees ambient temps.
I know that when you replace R12 with R134a you should use approx 80%. My understanding is that the Z required 32 oz. of R12 refrigerant...the shop invoice shows 26 oz. of R134a was installed which is approx 80%.
Are these readings normal for this car considering it has been retro fitted?

TRB on Mon July 04, 2011 10:00 PM

Is always a guess what pressures should or will be doing a conversion. Undercharging the system leads to poor lubrication. Low side seems little high for an expansion valve setup. But again it's a conversion. Which I take it you used the OEM condenser?

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Edited: Mon July 04, 2011 at 10:01 PM by TRB

Big Dawg on Mon July 04, 2011 10:45 PM

Yes...everything except the fittings, the refrigerant and PAG oil are the same.

TRB on Mon July 04, 2011 10:59 PM

Is it cooling to your satisfaction?

-------------------------

When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

Big Dawg on Tue July 05, 2011 8:29 AM

Well I guess as good as it can...I've noticed vent temps as I am driving of somewhere in the mid to high 50's.
In 1990 when I bought the Z unfortunately Nissan did not do a good job designing an AC system that worked well on very hot days. It wasn't till 1991 that they corrected the problem...so my Z was never great with R12 on 90+ degree days. I know it will be somewhat worse with R134a.
It has been 90 degrees or more for the last couple of weeks here so it is hard to say if it working as well as it can or not. Even though it has not been my daily driver for a number of years, I still maintain it well and want it to work as well as it can, that's why I was wondering if the readings are within specs on a retro fitted Z.