I have a 75 280z. I need to recharge the a/c. I got the r12 but I dont know where the low pressure side is. I need some help. Its getting hot out there !!

George, sorry if I don't know the exact answer to your question, but I'm sure you can find it in the Factory Service Manual (FSM) for your Z. You can find the full manual at the site below. It's a free downloadable PDF version of the manual. And they list the 1975 version.

http://www.xenons30.com/reference.html

_________________
Phil
1981 280zxt - Now in the care my son!
2014 370Z Sports Touring Roadster

The port on the back of the compressor is the low side port on my 76 Z with factory air.

_________________
-Dave
76Z Turbo'd
72 In Progress---DONE!

Sounds about right Dave. Low side has big hose, hi side has small hose if that helps. Also, for the price of R-12, it's wise to put the system in vacuum to make sure it's not going to just leak out. I'm also installing a pusher fan to help with the A/C, and replacing any door seal, ect that leaks air. The tighter the cab is the better it will work. Keep vents shut.

Much Thanks to Dave Paul and Phil

A clever little modification I did to the stock Z A/C system...

I intercepted the contact wires in behind the HVAC panel that turn on the compressor. I installed a manual compressor switch so that I can "turn on" the A/C in vent mode or bi-level mode. This is much more useful than the factory setup. The factory only lets you use the compressor in A/C mode, which is equivalent to the modern "recirculate" mode. The problem is that if you are in the rain or, high moisture, recirculate tends to fog the windows.

In VENT or BI-LEVEL, the outside air can be brought in, passed through the cold evaporator, and cooled or heated simultaneously. This is how humidity gets squeezed out of damp air. Think of it as a sponge. Hot damp air, when cooled, drops its water as condensation on the coil, then it gets re-warmed into warm or cool dry air for the cabin.

I don't know how Nissan missed this in their design. It's a simple switch in parallel with the contacts on the upper A/C lever. All original compressor controls are still retained.

If I ever get back there, I will document the simple mod.

Have a GREAT Memorial Day and thanks to all our people who serve!

_________________
-Dave
76Z Turbo'd
72 In Progress---DONE!

I'm not about to challenge either Paul (above) or Dave (2 or 3 posts
later), but I would like to ask for clarification. It seems to me that with
the A/C "on" you need somewhere for the incoming air from the A/C
outlets to go, otherwise you are inhibiting the flow of air. Sort of like
trying to use the A/C as a compressor for the air in the cabin.

It seems like my A/C works better with a window cracked open slightly,
so the cold air "doesn't have to work so hard to come in." If sealing up
the cabin were good, would we not also have to seal up the flow-thru
air outlets on the "C' pillar or on the hatch, as appropriate?

I'm also trying to process WHY the cold air coming out onto the wind-
shield should sometimes make it fog up on the INSIDE, while at other
times moisture forms on the OUTSIDE to the degree I have to run the
windshield wipers to clear it.................

All Z Best,.......................Kathy & Rick

_________________
All Z Best,.......Kathy & Rick

1969 Z.CAR (#00013 10/69) 8/30/76
1969 ITSA.Z (#00171 11/69) 8/24/73
1970 OLD.Z (#06289 6/70) original owner
1971 510 2dr since 12/31/75
1969 1600 rdstr (our 160-Z)
1971 (#19851 1/71) sold
1975 75.Z (#01343 1/75)

Rick's final statement is physically correct. Condensation forms on the WARM side of a surface. That's why the outside of your "iced tea" glass or can gets wet on a hot day.

(Yeah, yeah, I know ~ it's wet INSIDE too, but not from condensation )

Frank

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1970 240Z

In cooler damp weather, the windows can steam up on the inside of the glass. Especially when you have the A/C selector set to the A/C position. In that mode, the air from INSIDE the car is fed back into the system and spit back into the car. It's recirculate. No need to crack the windows, in a 280Z. It's an air loop. Not ideal for de-humidifying, but lessens the load on the A/C system. That is why Nissan did it this way. It's easier to cool 70 degree cabin air to 50 degrees than to take 90 degree air from outside and cool it to 50 degrees. Using VENT or BI-LEVEL will suck outside air into the car, but you can't cool it with the stock HVAC system. My cheater button lets you do just that, like a modern automobile system can. You can even select DEFROST and cool the A/C coil at the same time, for warm dry Arizona-like air.

A/C is great at taking dampness out of the air. It does so by default IF the moist air is significantly warmer than the coils. You see, by being able to engage the heater core AND the A/C coil, you can warm the cabin air AND extract the moisture on cool damp days.

You don't get foggy windows in modern cars....the above description is precisely why.

Remember this. Whoever reaches dew point first, gets wet. The dew points are different for inside and outside when you run the A/C or heat.

Don't EVER take a Z out of a cold garage into a high humidity environment. Moisture WILL condense inside of the body panels and frame members. It's REALLY bad for the inside cavities of a Z to be wet.

Vacuum pump the system with a proper pump before charging. Make sure it holds vacuum overnight. It is illegal to charge a system with a leak. Not that I am not guilty of it myself. We all goof sometimes.

_________________
-Dave
76Z Turbo'd
72 In Progress---DONE!

ThankZ for the explanation, Dave, I THINK I get it.
But now, as for the quote above concerning not taking a Z out of a cold
garage into a high humidity environment: WHAT'S THE SOLUTION

1) Dehumidify the outside environment (I don't think anyone makes a
dehumidifer big enough to do that)

2) Have the garage heated and HUmidified (kind of expensive; I
guess that's why renting those climate controlled units costs so much)

3) Wait for a nice cold, low humidity day to drive out into.....

4) Open the garage door and let the inside temperature and humidity
come into ambience with the outside air (seems like I would still be
exposing the cold Z to the humid air rushing into the garage)

Now everyone is beginning to learn why all my education is in Military
Science and Tactics, and Business Administration-- not in physical
sciences and engineering

All Z Best,........................Rick (and Kathy, of course)

_________________
All Z Best,.......Kathy & Rick

1969 Z.CAR (#00013 10/69) 8/30/76
1969 ITSA.Z (#00171 11/69) 8/24/73
1970 OLD.Z (#06289 6/70) original owner
1971 510 2dr since 12/31/75
1969 1600 rdstr (our 160-Z)
1971 (#19851 1/71) sold
1975 75.Z (#01343 1/75)

Hah Rick, I spent quite some time studying thermo dynamics, HVAC, heat transfer...

The best idea is to keep the car inside a relatively closed/sealed garage, or wait for a day when the dew point is higher than the temperature of your garage. On days when it really gets hot quickly in the morning, with high humidity, I turn the heat on in the garage for an hour or so, if its cold inside, to get the garage and the car over the dew point. Obsessive? yeah probably.

My thin walled storage sheds follow out door ambient temperature pretty closely (or hotter when the sun hits them - hotter is gooder) , and keep moist air from pouring in, so that condensation is not a problem. Sealed storage is better than vented, contrary to popular belief.

Keep your crawl spaces CLOSED. Unless you have radon!

#4 is NOT a good idea. Your garage floor will get wet, and your Z will get wet.

#1,2 and 3 are good ideas. #1 is a tuffy!

_________________
-Dave
76Z Turbo'd
72 In Progress---DONE!

Dave, you couldn't have made your post at a worst time for me.

Last evening, I took the Z out for a quick ride. It hadn't seen the outside for a few weeks. My garage has a concrete floor and two concrete walls, which means it stays nice a cool most of the time. The minute I drove out into the driveway the car was instantly covered in condensation! I've never seen it that bad. My son asked what was wrong with my fog lights until he noticed the moisture was on the outside of the lens.

Racked with guilt.....

_________________
Phil
1981 280zxt - Now in the care my son!
2014 370Z Sports Touring Roadster