1977 280z AC -- issue # xx of yy

[Dave WM]

low side is fire wall to compressor, High side is compressor to condenser in front of the radiator. On the SWP123 the back is the low side, the middle is the high side. you can also look for a D for discharge (high side) and a S for suction (low side) stamped on the case of the compressor.

the hookup to the gauges is you remove the brass screw on caps on the compressor and then you hook up the hoses, they are old style screw on, not the R134 push on. Would need to see your gauges to know what you have. The assumption is you have no R-12 currently as bleeding it into open are is not legal. So assuming its all leaked out you will have no pressure, so after attaching the hoses (gauges should read 0 psi both high side and low side). you hook up the vacuum pump, open both the gauge valves, turn on the pump and you should immediately see a vacuum. the high side does not read neg pressure so just keep watching the low side. You should get to -29 if you have a good pump and no leaks. Once there close off both gauge valves, turn of  the pump, and watch the low side. If it holds you may luck out. if it does not you will need to replace the pump with compressed air or better still nitrogen. open up the valve from the nitrogen then crack open the low side valve on the gauge, assuming you started at zero just allow the pressure to build to about 70psi. Don't go higher, no need for testing for leaks, get some soapy water and spray around the hoses, compressor, drier, any fittings and esp the front of the condenser. look for bubbles to form. Often you will also see oil stains, esp on the condenser that is also a sign of a leak.

 

Edited August 18, 2020 by Dave WM

[Dave WM]

here is a video talking about AC

 

[240zadmire]

@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.

regards

 

 

[240zadmire]

I have 2 questions about the switch mounted on the receiver drier

- Is it binary or is it bipolar?

- what PSI does it operates?

 

regards

 

[Dave WM]

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.

[240zadmire]

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

 

regards

 

[Dave WM]

300psi is so if something goes bad wrong it will shut off, you want some head room as its only to prevent damage in case of major problems. The primary cycling is done by the thermostat.

Edited August 19, 2020 by Dave WM

[240zadmire]

Greeting!

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 August 10, 2021 by 240zadmire

[Dave WM]

congrats! yes there should be a hole for the condensate hose.

[S30Driver]

You should be able the find the drain hole near where the carpet ends in your picture, under the drain tube.

[240zadmire]

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 when park in the garage.  

 

[Dave WM]

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 August 11, 2021 by Dave WM