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280Z heater water valve


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1976 260Z with Factory AC. Auto adjusting temp control.  No heat modulation to speak of. As soon as I move the temperature control from full cold to warm, I get a blast of full hot air. No modulation of Temperature at all. Moving temp control the slightest bit ( less than 1/4" ) gives full hot air.

 

Auto Kock ( 27116-N4220 ) seems to be adjusted properly as per FSM, so I have a sneaking suspicion that this valve is stuck open or the internal O-Ring is leaking and allowing hot water to bypass.

 

Vacuum controlled water valve seems to be working properly. It's either closed or wide open. And I can shut heat off entirely if I move the Temp lever to Full Cold. So that would indicate that the Vacuum controlled " secondary " water valve is working correctly.

 

Question is. How hard is it to remove the complete Auto Kock assembly with it's capillary tube? The valve itself is reasonably easy to get at, but the capillary tube looks like it terminates behind the heater core or evaporator? I sure as heck don't want to pull that mess apart!! Looks like an SOB to get at.

 

Any one pull one of these units before and can give some advice? Can you convert to the manual style water valve? ( 27116-N3600 )

Edited by Chickenman
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  • 2 months later...

I've searched for years to an answer for this problem myself. Same issue on my 78

I've been having the same issue for years on my '78 as well.  Since mine started leaking recently I've decided to make this more of a priority.  I've got the valve out of mine and have been looking it over a bit.  

 

There is an adjustment in addition to the adjustment of the cable that they don't mention in the FSM.  The capillary tube is connected to a small piston that pushes on a lever in the water valve - the idea being that if the air in the heater gets too hot the liquid in the capillary tube expands and closes the water valve a bit. You can see it in this pic:

 

https://goo.gl/photos/9ifNLxjAPpDZy6qcA

 

The small Phillips screw moves the lever that the piston pushes on, and appears to change the pivot point such that the piston can have more or less of an effect.  It looks like turning the screw clockwise will increase the effect of the capillary feedback.  If nothing is leaking currently then perhaps try adjusting the cable per the FSM, and if that doesn't fix your problem, try turning the screw a little bit at a time and see if that has an effect.

 

Since mine was leaking, I've also replaced the diaphragm seal which is still available at NAPA (660-1000 Balkamp repair kit) - there's a good writeup on zcar.com on this.  It turns out that this valve design had been in use for many years before our Z-cars - do a search on "Ranco H-16"  and you'll find many well documented writeups on repairing the seal on these.  Weirdly, I didn't see anybody talking about the adjustment screw though.

Edited by TimZ
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I've been having the same issue for years on my '78 as well.  Since mine started leaking recently I've decided to make this more of a priority.  I've got the valve out of mine and have been looking it over a bit.  

 

There is an adjustment in addition to the adjustment of the cable that they don't mention in the FSM.  The capillary tube is connected to a small piston that pushes on a lever in the water valve - the idea being that if the air in the heater gets too hot the liquid in the capillary tube expands and closes the water valve a bit. You can see it in this pic:

 

https://goo.gl/photos/9ifNLxjAPpDZy6qcA

 

The small phillips screw moves the lever that the piston pushes on, and appears to change the pivot point such that the piston can have more or less of an effect.  It looks like turning the screw clockwise will increase the effect of the capillary feedback.  If nothing is leaking currently then perhaps try adjusting the cable per the FSM, and if that doesn't fix your problem, try turning the screw a little bit at a time and see if that has an effect.

I just got my HVAC back together today, and can verify that this did indeed work.  I can now get incremental changes in outlet air temps like one would expect!  I initially had the screw adjusted too far clockwise, and the capillary feedback was preventing me from getting full heat.  Backed it off about a half turn and it's now working correctly!

Edited by TimZ
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