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1977 280z AC -- issue # xx of yy


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@Dave WM

thank you sir. I’m still reading to get more understand and hopefully by weekend, rent the tool at autozone or oreilly and see if I can check the leak.

This is my first time working on AC.  It’s been upper 90 degree in California lately. If the system is sealed,i it would be a cool breeze for sure.




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not sure what binary refers to, its on and off, off it pressure exceeds 300psi IIRC. its a high pressure cut off to prevent failure if something were to plug up and now allow Freon to flow. Later model cars used a low pressure switch to prevent it trying to run if the Freon leaked out. still later models had hi/lo cutting off if it was too high or too low, and then some added a fan option to turn a fan on at a threshold pressure, I think the binary/trinary references started up with those.

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That’s quite high.  If convert to r134a, isn’t that r134a pressure lower? Like 225psi?


on another note, the high pressure switch wires broke flat broke off to the switch.  Look like it’s hard silicone or glass.  Wonder if the switch still good to try to salvage.


another note is that to hot wires the high pressure to see if compressor clutch work, turn out clutch still good to go.  Will wait for the after market drier receiver and pull the vacuum




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  • 11 months later...
Posted (edited)


I skimmed the gym’s sauna last could of months by using my sauna on wheel but can’t stand it anymore.  When the car is moving I guess it’s bearable, but boy, people saw me wipe sweat off of my face at red lights … I can see their sympathies in their eyes….

below was how I did it.  Hopefully it can help somebody learn from my experience or avoid my mistakes.  Keep in mind I’m not a mechanic let alone AC specialist.

the R12 to R134a valves conversion do  not work.  Parts are below



All I did was remove the caps and screw the new valves on top of the old ones.  The high valve is toward the radiator, the low valve is toward the firewall.

I follow the online instructions of how to pull the vacuum, close the valves at the gauges and turn off the vacuum pump.  Left it like that for 12+ hours.  Seem like there is no vacuum leak after more than 12 hours with 29psi solid.



i used 3oz ester oil and 2 can of 12oz R134a without any additive from Oreily.  Some one from this forum and other places suggest to put approximately 80% of R134a as molecular is lighter, operate at higher PSI.  So I put in approximately 18oz of r134a

Outside temperature was in the mid 70.  After 3oz of ester oil and 18oz of Freon, cabin temperature measure was about 50 degree.  I’m so happy.  Been running almost every other day for 30mins to 1 hour happily without wiping sweat off of my face.  Other avid drivers were surprised why my windows were up mid afternoon knowingly cars this era often than not, no AC.  

last couple of days, I notice when I made a sharp right turn, about a tea spoon of water splashed on my right foot.  Closer examine under the evaporator under the radio, there is a, suppose hose connector to drain the condensed moisture.  I suppose it need to connect to that hose and down the transmission housing.  You can see a drop of water about to fall.  I couldnt find the hole on top of the transmission housing.  Perhaps my carpet/sound deadening cover it.  Can someone confirm?





Edited by 240zadmire
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You’re right.  Looked back at old photos and there it is.  Got the hose hook to the tube and it actually quite a bit of condensation.  Probably about 2 full spoons of water C0A541FC-3E17-4085-81EC-71D7E3CE6349.jpegwhen park in the garage.  



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Posted (edited)

Its SO much nicer with a working A/C. I took mine out for my weekly trip to the park, 98f 70% humidity. If I did not have A/C the car would have never left the garage. With the OD 5 speed, A/C, and the new rad, I can cruize 70-75 at about 2.7k, windows up so I can hear the stereo, enjoy the ride. its a 35 mile trip on way to the park, the temp gauge never moved of the middle of the E in TEMP.

Edited by Dave WM
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  • 2 months later...

Dave, I stumbled over your idea to "gut the original valve" and use it as a manifold. I will follow up with more pictures when it is finished. Best Regards from Norway.



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  • 4 weeks later...


The manifold for the new valve is mostly finished, I have not removed the "inboard end" just in case it will need more machining. I will also have to make a steel plate similar to the "flange" on the original valve. This loose plate will enable the manifold to be rotated, to orientate the inlet of the new valve in the desired direction. I decided to make a hose connection so that I can use the manifold also for the flushing of the evap. The first flushing adapter, as shown in the picture in the post above, was made from 40mm Al, which is to small (you can see the O-ring). The new manifold is made from 50mm Al. It is winter now so this project will be on hold until....later. I have ordered an elbow just to line up the inlet to the new valve, not sure if it will fit. The alternative will be to just make a hose from the connection in front of the Fire Wall to the new valve. 




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