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Heater Control Valve 76-78 280z

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I've been struggling with the heater in my 77. The first 2 years I owned it I periodically replaced vacuum lines as they cracked. I've now replaced all the lines under the hood, yet my heater still doesn't work (same symptoms as cracked vacuum lines). My car has AC but I have no need for it (belt removed currently, eventually I'll ditch the rest of the system). I have no reason to turn on my blower for any reason except wanting heat, and I could live with it just blowing through the defrost, which it doesn't do without vacuum it seems.

 

Could I simply bypass the valve altogether to gain reliable heat?  

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There are some very simple 1/4 turn valves available for common household 1/2" water lines that can be substituted for you current valve. 1/2 lines fit very nicely into standard 5/8" heater hose. That way you can at least adjust the heat and turn it off when it you don't need it. If defrost is all you want you can mechanically fix the linkage to that position. Vacuum control suck, especially 40 year old ones, but I don't have to tell you that!

 

There are some really nice aftermarket remote controlled heater valves out there like this one from Vintage Air.

 

http://www.vintageair.com/2014catalog/Pages%20from%202014%20VintageAir%20Cat%20rev%208-15%2090.pdf

Edited by z240

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Thanks! That looks like it could be the ticket, though I'll start with a generic valve.

 

Apparently my understanding of automotive HVAC is quite flawed. I assumed the heater temperature was controlled by mixing air off the core with fresh outside air. I take then it's based on water flow to the heater core?

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Heater temperature is controlled by the temperature control valve that regulates radiator water flow through the heater coil. That's what the slide switch on the bottom of your climate control panel controls. The slide bar that goes from vent to heat to defrost controls a series of vacuum operated damper valves that open/ close to direct the air flow coming off the heater coil to the cabin or the windscreen. When in the vent mode it closes off air flow through the heater core and direct a the air straight into the cabin.

If all the vacuum hoses are intact and your controls are properly hooked up you may have some faulty vacuum actuators. Only way to fix that is to replace them. Mine are now 38 years old and still working fine. Then again, it also helps that the vacuum is being provided by an LS1. :-)

Edited by Phantom

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Apparently my understanding of automotive HVAC is quite flawed. I assumed the heater temperature was controlled by mixing air off the core with fresh outside air. I take then it's based on water flow to the heater core?

Attached a sample from the FSM.  It's in the Air Conditioning chapter.  The small vacuum hoses at the vacuum solenoids tend to split and leak.  One sign of no vacuum is cold air from the center vent at all settings.  The vacuum bottle needs a good source.  There's electrical valves that need power (can't remember if they're normally open or closed).  It looks like some engineer had a wild idea and nobody stopped him in time.  It's a mad house.

 

If you have a fairly intact system, don't tear it apart assuming you'll be able to figure things out later.  There's a lot of hoses and nipples and the labels on them don't make much sense.

 

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

post-8864-0-21316100-1431106034_thumb.png

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Thanks, I'v looked at that diagram before and it makes it look relatively simple, the main issue is identifying which nipple is which on the vacuum selector valve, does anyone have any input?

 

Taking the dash out to repair cracks is on the to-do list. Maybe I should get on that and take the opportunity to thoroughly go over the heating system. 

 

Also, does anyone know what the "magnetic valve - vacuum source" does? Any reason it couldn't be bypassed?

Edited by m1ghtymaxXx

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49F842AC-48B4-4DEE-B547-FCE8DA8B9886.thumb.jpeg.9e86e65e03d3b7df7f30647a959e7e24.jpegFWIW.

On 350559 August 1976 280z

Interior heater water control valve is actuated with copper capillary “A” & “B” sleeved control rod connected to the TEMP -COLD/HOT lever.

No vacuum activation on these late models.

 

ZCar Source currently has a package SKU:K22100352

It includes the 3 hoses, and

(core swap exchange)

control valve c/w capillary tube and temp sensing unit.

FE331D21-ABB7-48E2-9951-5F361A00DCB0.jpeg

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