I've got no heat.

[Driver_X]

77 280z, 5spd, factory AC. AC works great, but I've got no heat. Bled cooling system again, no air in system as far as I can tell. No overheating issues. I'm thinking blockage somewhere. Probably valve under dash. Visual inspection of valve and it looks pretty good. No evidence of leaks. Bur I guess it could be bad inside.

Lack of heat is not a huge deal because I put the car away for winter, but everything else works in car and it kinda bugs me. Any suggestions?

Edited August 27, 2015 by Blue
hest to heat

[FastWoman]

I assume your '77 HVAC is like my '78.  There are 2 stopcocks that control coolant flow to the core.  The first is pneumatically controlled and is "on/off."  The second is mechanically controlled and can be opened and closed variably to control how much heat you get.  My guess would be that your pneumatic controls are leaking or disconnected.  Part of the problem can be the mode selector switch, which switches vacuums to the various actuators, and which can become dirty and leaky as the grease hardens.  It's relatively easy to refurbish.  See here:

 

http://www.classiczcars.com/topic/32856-refurbishing-the-hvac-vacuum-selector-valve-in-a-1978-280z-useful-info/

[Zed Head]

77 280z, 5spd, factory AC. AC works great, but I've got no heat. Bled cooling system again, no air in system as far as I can tell. No overheating issues. I'm thinking blockage somewhere. Probably valve under dash. Visual inspection of valve and it looks pretty good. No evidence of leaks. Bur I guess it could be bad inside.

 

You have your "heats" a little blended together and mixed up.  Engine heat will show up on your Temperature gauge.  If that's correct, then no need for bleeding, or looking for blockages that could cause overheating.  The cabin heater just takes a small amount of coolant fromthe back of the head, runs it through a small radiator in the cabin, then sends it back to the water pump.

 

But, as FastWoman said, it's probably your "vacuum **** (rooster)".  Here's a link with diagrams and complete explanations of the AC system.  My 76 would bust a hose every few months until I patched together some new flexible hose on the ends of the old brittle hose.  AC chapter.  76 or 78 is probably the same, if you can't download the complete giant 77 FSM.  Start in the engine bay, it's easier than behind the control panel.

 

http://www.nicoclub.com/FSM/280z/

Edited August 5, 2015 by Zed Head

[Driver_X]

Ok, I read through fastwomans link and while I don't yet completely understand it, as an added symptom, when I turn on the AC,my idle drops. If I understand it correctly, this means I have a vacuum leak in one, or all, of those little lines in the engine compartment because that's not supposed to happen.

Right?

[siteunseen]

The vacuum hose going to the fast idle actuator may be cracked or loose.  When they are working properly it will pull back the throttle rod raising the idle to compensate the drag from the A/C compressor.  Quick picture I grabbed off google, maybe you can see what I mean.  FICD is "fast idle control device"

 

[Zed Head]

Ok, I read through fastwomans link and while I don't yet completely understand it, as an added symptom, when I turn on the AC,my idle drops. If I understand it correctly, this means I have a vacuum leak in one, or all, of those little lines in the engine compartment because that's not supposed to happen.

Right?

Probably.  There's a supply hose from the intake manifold over to the big white bottle on the passenger side fender well area.  I've had that hose split also.  It's a very small port, kind of like the one on the bottom right in site's picture.  My 76 has it more to the left of that spot though.

 

With the engine running, pull the hoses from the bottle and see if there's vacuum.

[Patcon]

Do you have an "FICD"? If so check the lines for leakage. Like Zed said check the vacuum bottle also..

[Zed Head]

He's probably looking for the big white bottle.  Could be that somebody removed it to "clean up" the engine bay.

[Driver_X]

Everything is there, I just need to find a few minutes to really start looking at these lines and see what I can find.  Thanks for the leads.  I was thinking that I had an air bubble in the heater core (this is my first water cooled car that I've worked on, previously I've only dealt with air cooled VW & Porsche, so when I put in a new radiator last year, I forgot to open the heater control valve when I was adding the coolant).  I'll report back once I get a chance to take a closer look and do a little investigating.

[Driver_X]

Ok, I now have heat! (Or hest, according to the title of my thread)

The two short hoses at the vacuum canisters on the passenger side were completely deteriorated. They're pretty hidden, so once I knew where to look, it wasn't hard to figure out. I also changed the end of one of the hoses on the intake manifold and checked all other connections.

I also have a working FICD valve, however it doesn't quite have the strength to actually move the throttle linkage. It moves all but the last 1/32", which when I help it, will raise the idle to about 1200 rpm. I hoping this will improve with use.

Many thanks to all that responded!

Edited August 25, 2015 by Driver_X

[siteunseen]

Congratulations!  Hest is good. 

[rossiz]

hest is the best, lest you freeze like the rest - mornings are cool this time of year...