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Ranco H16 Heater Control Valve Question

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AMXrated View Drop Down
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    Posted: Dec/24/2018 at 12:09pm
I have a 1972 AMX that has a Ranco H16 Heater Control Valve.  From what I have read, the 71/72 models were the only ones to have this component.  Mine still functions, but the seals are shot which is not a complete surprise.

Before attempting what sounds like a near-impossible rebuild or paying out the wazzoo for a replacement on Ebay, can someone tell me exactly what this thing actually does?  

I get that it controls flow through the heater core, but what is the purpose of the complex system of springs and control bulbs?  Doesn't the cable on the temperature selector actually control the valve?  If so, I think I can make something simpler work without risking coolant dumping on my passengers feet.

Thanks.




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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: Dec/24/2018 at 12:20pm
Originally posted by AMXrated AMXrated wrote:

I have a 1972 AMX that has a Ranco H16 Heater Control Valve.  From what I have read, the 71/72 models were the only ones to have this component.  Mine still functions, but the seals are shot which is not a complete surprise.

Before attempting what sounds like a near-impossible rebuild or paying out the wazzoo for a replacement on Ebay, can someone tell me exactly what this thing actually does?  

I get that it controls flow through the heater core, but what is the purpose of the complex system of springs and control bulbs?  Doesn't the cable on the temperature selector actually control the valve?  If so, I think I can make something simpler work without risking coolant dumping on my passengers feet.

Thanks

I think the bulb thermostat to the valve is to regulate flow when coolant is hot. 

I had a 73 and in comparison to my 71 valve, the 73 vacuum operated one had the same flow no matter how hot the coolant got.

I restored my valve and it was not that hard to do. The big issue is bending the tabs to hold the valve to the mounting plate.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote scott Quote  Post ReplyReply Direct Link To This Post Posted: Dec/24/2018 at 1:27pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AMXrated Quote  Post ReplyReply Direct Link To This Post Posted: Dec/26/2018 at 1:50am
@scott:  Thanks for the reply and link.  I may try the rebuild and see what happens.  

I am still not clear what the sensing bulb is actually doing since the valve gate appears to mostly controlled by the cable from the temperature selector.  For example, if I get in the car when it is cold outside and move the temp slide all the way to high, coolant is going to flow through the heater coil.  If it gets too hot in the car, and I slide the lever to low, it will close the valve stopping coolant from flowing to the heater coil.  However, it seems like the sensing bulb will cause the gate to still open slightly thus allowing some coolant to flow to the coil, even though I really don't want it to.  

The car is not assembled right now so I can't test it to see what is really going on.  Am I missing something in the function of the heater valve?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote FSJunkie Quote  Post ReplyReply Direct Link To This Post Posted: Dec/26/2018 at 5:08am
The heater valve is actually a thermostat and works in much the same manner as the air conditioner thrmostat. The valve's thermal capillary tube senses the output air temperature of the heater and regulates the flow of hot coolant through the heater core to maintain a set output air temperature. The valve increases coolant flow if the air temperature drops below the valve's temperature setting, and the valve decreases coolant flow if the air temperature rises above the valve's temperature setting. The cable to the dash control sets the temperature setting of the heater valve. The extreme cold position of the control locks the valve shut no matter the air temperature and the extreme hot position of the control locks the valve fully open no matter the air temperature, but in between the valve has thermostatic control of it's opening.


It's more complicated and unreliable than a blend-air method of regulating heater air temperature, but it's the older and arguably superior method for passenger comfort. Except for the extreme ends of control movement, the heater valve will regulate the temperature of the heater outlet air regardless of blower motor speed, engine speed and load, vehicle speed, or outside air temperature. The heater outlet air temperature will always be regulated at the temperature you set the control to.


With an AMC utilizing an Ranco thermotatic heater valve and a thermostatic air conditioning thermostat, it is theoretically possible to leave the heater temperature control set at 65 degrees year-round and leave the A/C temperature control set to 75 degrees year-round. The two thermostats will act together to always maintain the air temperature leaving the vents at between 65 and 75 degrees. Theoretically. Not ideal since vent air temperature does not always reflect car interior temperature, but it is theoretically possible.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Dec/26/2018 at 5:52am
WWon't  hurt  a thing  to replace the Ranco with a simpler valve. Many do. It's not always so easy to repair it, depends on condition. Of course I've only dealt with early 60s versions... the same, just older.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AMXrated Quote  Post ReplyReply Direct Link To This Post Posted: Dec/28/2018 at 7:01am
Thanks for the info.  
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