Heater control and its function

[IdahoKidd]

For those who have followed along in a different thread, you know I have been chasing an engine no heat problem. I "may" have that fixed. It "may" have been an air blockage. That problem aside, I have most of the underside of the dash apart to inspect the heater control valve. When chasing the other problem, after moving the control in the cabin from hot to cold back and forth rapidly, I lost coolant flow through the heater core (as determined with the 5/8 hose off the core under the hood. I suspected I bent the wire. However, everything moves like it is supposed to. I took a separate piece of hose and tried to blow through the heater core. There was no movement of air or water. Moving the control several times and blowing again, quite firmly, it purged coolant and I can now blow freely through the core.

So the question: I can blow freely through the core with the control in the warm AND the cold position. I can see there is a small diameter copper tube that runs to the valve. I can't determine exactly what it' function is, but how do the two interact? What tells the valve to restrict the water flow to keep the heat in the heater core? Should I be able to blow through the valve in any position? (this is a 77 280, non a/c, manual operated via wire, not vacuum)

FWIW, I bought an FSM online in disc form. Put it in the computer and it locked up the computer. After getting it rebooted, I can not get the disc drawer to open or the computer to read the disc. Short story, I don't have a manual. I have part of today off and would like to put the car back together but don't want to do so if I have to take it apart again. I do have another manual ordered but really don't want to wait that long. Is there a simple way to confirm the control valve is working properly?

Thanks!

Leonard

[sblake01]

Here's a link to a 77 FSM in pdf:

http://www.xenons30.com/files/FSM/77_datsun_280z.zip

[IdahoKidd]

Thanks. However, I can't get that link to open.

[Reverend]

Try Mozilla, for me it opens right away

[sblake01]

It opens for me in IE8.

[FastWoman]

Hi again, Leonard,

Mine is a 78, not a 77, so I don't know if there are differences between our systems. There are TWO, not one, stopcocks that control water flow in the 78. The first is vacuum actuated, and it is used to turn water flow either fully on or fully off. Its purpose is to allow temperature control in the AC position without actually introducing engine heat (a nice feature, IMO). This valve receives its vacuum from the vacuum control switch (the mode switch) and should receive vacuum in any of the heat settings. The vacuum control switch can become leaky as its grease hardens and gets dirty. (Mine was leaky.) You can pull it apart, clean it, re-grease, and reassemble with minimum difficulty. Just be sure to mark all your positions. As I recall, there are a couple of notches on the valve parts that line up in the defrost position (???).

The second stopcock is opened and closed gradually via the temp control wire.

If you can blow air through your core without the engine running (i.e. no vacuum), then I'd say your vacuum actuated stopcock might be stiff/frozen and stuck open. It might sometimes get stuck in the closed position too. If you follow the vacuum line into the recesses of your dash, you can feel the thing and confirm by feel whether it's opening and closing properly. You'll need to have the engine running, of course.

[IdahoKidd]

The file from that website has been independantly confirmed as corrupt and won't open.