How's this supposed to work anyway?

[jvandyke]

My kid made me drag home a '72 240z.  It's pretty cool.  Now it's cold outside.  We'll put it away soon Mom, we promise.  But in the mean time, how about some heat?  So I'm trying to figure out how it's supposed to work.  Car has A/C.  As of right now turning on the fan blows air out the side and middle vents.  What is supposed to redirect the air to the heater box and associated ducting?  While we're at it what turns the AC compressor on/off?  I assume the one fan motor, in the A/C stuff (passenger foot well) blows for both cold and hot, and something in the controls somewhere is supposed to direct that air in the right direction.  There's a control cable that heads over and behind the A/C stuff, is that the guy not functioning?   Not sure which aftermarket version it is.  Not interested in trying to get the A/C functional again (next summer probably!).  Just curious how these would have been set up typically, dealer added and all, I assume.  Maybe some PO hijacked the fan control for the A/C unit leaving the OEM fan inop?  Totally guessing.

BTW, this little gem (sarcasm) is powered by a Chevy 350zz4.  Just saying, she's a long way from how it left the factory.  Not judging mind you.  If I could wave a magic wand and put it all back to OEM I would, but well, in the mean time, holy cow can this machine tear it up.

Edited October 22, 2018 by jvandyke
more info, picture

[jvandyke]

So when they added A/C, what does the oem fan (in the OEM heater box) do?  Is it still in play?

[gwri8]

You're going to have to show pictures to clarify your car's situation, especially with the AC.  But typically with the stock version of the heater, you simply slide your controls to heat and hot and of course turn on the blower fan.  Hot air should only come out of the heater vents or the defrost, whichever is selected, not the center or side.  That is unless you have some other aftermarket kind and I am not familiar with any of those.  Someone with more V8 and 72' experience will probably chime in soon.  Good luck!

[jvandyke]

Yep, that's my question.  The A/C is aftermarket (they all in '72, or dealer installed, same difference I guess).  How would it typically work for the system to know which fan to run; heater box or A/C, or in the case of A/C does that install render the heater box fan inop? The fact it's got a V8 is irrelevant I would think. I just don't know how it is supposed to work "typically", I can trouble shoot from there once I know what it's supposed to be like ,then figure out the string of previous owner's and their hacks, then "fix" it my way. Here's the heater valve, FWIW

Edited October 22, 2018 by jvandyke

[gwri8]

Hence the request for more pictures of your AC.  Under the dash, console controls and other side of the firewall to start.  That will show more info than trying to explain everything.  The folks on this forum are sharp and can pick out details that could solve your AC questions quickly.

[jvandyke]

okay, added the one other picture I currently have, will take more, the controls look stock '72 to me, the cable that runs to the AC and disappears behind, that one I don't know it's purpose, could be the culprit

[siteunseen]

On my '72 that cable pulls the valve open for heat.  Pushed all the way to the firewall is closed, no heat.

And if I remember right that cable that disappears pulls open a metal flap that is between the fan and the condenser. 

Edited October 22, 2018 by siteunseen

[jvandyke]

The heater control valve cable I got a handle on, well it's pivot clamp is jammed so it doesn't work well from the controls but can be moved manually, so the valve is open, in theory, letting hot juice inside the heater core (in theory).  The one that disappears behind the A/C unit might be the problem then, if it's not closing then air is going to the condensor box and then the center and side vents, if closed it should re-route the air into the heater box and then to floor/defrost depending on setting, yes? sounds like I have to get back there and free it up, or at least force it closed for the fall.  These cars are fun to work on, I mean that sincerly, I love mess'n with my son's car.  The pay sucks though.

Wait, this might help;

http://datsunforum.com/wp-content/uploads/2014/11/Datsun-240Z-Sport-1971-FSM-Supplement-16.jpg

if that's what we have in there.....

if so, then I'm wrong the air deflection occurs in the "heater" box, near area labeled "6", closing off section 7 (center vent) and 24, 26 (side vents), maybe?

I don't think that's the unit we have though.....

Edited October 22, 2018 by jvandyke

[Patcon]

That image should be what most of the under dash stuff should look like. Although the AC gets added in near the fresh air stack. IIRC there is only one fan for the whole system. There is a diverter to direct air through the evaporator or the heater core. From the looks of the evaporator housing that is the dealer add on AC. Normally there is a small pod mounted on the center console near the drivers right knee that had a knob and a toggle switch. The know was to select temperature and the toggle switch controlled the AC clutch.

[gwri8]

You can download a 240 FSM here.   http://www.xenonzcar.com/s30/fsm.html

That will be your new bible for the car.

[jvandyke]

Yep, i've got that FSM, can't find where it talks about this stuff though, I'm probably missing it.

[jfa.series1]

Let's presume your dash controls look like this.  The top lever is for (1) a flap to open or close an opening from the cowl, and (2) another flap that manages the direction of the fresh air inside the heater box.  When in the off position, no outside air comes in and the flap to admit cabin air in to the heater box is open.  This is where your A/C system would be routing air.  Air flow comes out thru the center and outboard vents.  The center lever is pretty self-explanatory: it manages the water valve to block or admit hot water to the heater core.  The bottom lever shifts air between defrost or room.  The owners manual says this lever has "no relation" when the vent is open.

The aftermarket A/C system has to use the above.  It is the equivalent of "recirc" in a modern system - no fresh air.  If you have the top lever anywhere but OFF, you dumping outside air into heater box and defeating the A/C.  Adding to the problem is the blower fan in the heater box is trying to pull air thru the A/C, an inherently poor solution.  None of this has anything to do with the V8 conversion UNLESS they also messed with stuff in the cabin.  Hope this helps a bit.

Edited October 23, 2018 by jfa.series1