heater valve on firewall

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   I'm hoping someone can explain to me the function of the heater valve mounted on the firewall of my 1971 Javelin and the factory correct hose routing. This is on a resto project. I currently have hose from water pump going to heater core, and another from heater core to intake fitting, bypassing the valve. When car is running heat is coming into passenger foot area. I have service book but it has very limited info about valve. Thank you for any /all help. Spring is coming!!!!

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390ina71jav Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Apprentice Joined: Feb/09/2017 Location: Connecticut Status: Offline Points: 58	Post Options Post Reply Quote 390ina71jav Report Post Thanks(0) Quote Reply Topic: heater valve on firewall Posted: Feb/08/2023 at 5:48am
	I'm hoping someone can explain to me the function of the heater valve mounted on the firewall of my 1971 Javelin and the factory correct hose routing. This is on a resto project. I currently have hose from water pump going to heater core, and another from heater core to intake fitting, bypassing the valve. When car is running heat is coming into passenger foot area. I have service book but it has very limited info about valve. Thank you for any /all help. Spring is coming!!!!

PROSTOCKTOM Members Profile Send Private Message Find Members Posts Add to Buddy List Supporter of TheAMCForum Joined: Jun/20/2010 Location: Indiana Status: Offline Points: 2450	Post Options Post Reply Quote PROSTOCKTOM Report Post Thanks(0) Quote Reply Posted: Feb/08/2023 at 6:12am
	It's just an on off valve that is used to regulate the flow of coolant running through the heater core. If you bypassed the valve then you have no way to regulate the cabin temperature or turn off the heat in the warmer months. Tom Edited by PROSTOCKTOM - Feb/08/2023 at 7:45am
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Trader Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: May/15/2018 Location: Ontario Status: Offline Points: 6877	Post Options Post Reply Quote Trader Report Post Thanks(0) Quote Reply Posted: Feb/08/2023 at 7:43am
	If your "restoring" you may want to post in the restoration section as the AMC heater control valves is a "heated discussion":) There are 2 firewall mounted valves of the "era" 68-74: https://www.amclives.com/products/heater-water-valve-fire-wall-mount-select-amc-inline-6-and-v8-see-applications What came on my 69 Base Javelin, have seen a few of these at shows: Both used the same intake connection tube: And what people call correct that isn't firewall mounted: https://www.amarkamc.com/product.sc?productId=334 Years and models these came on 68-74 has also been questioned before. Good luck! Please post again here if you do get an answer. Edited by Trader - Feb/08/2023 at 7:46am

scott Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jul/10/2007 Location: Wildwood Pa. Status: Online Points: 3500	Post Options Post Reply Quote scott Report Post Thanks(0) Quote Reply Posted: Feb/08/2023 at 8:13am
	Here's how your valve should be connected. This is a 1971 Javelin. Photo credit goes to Kirkwood.

Trader Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: May/15/2018 Location: Ontario Status: Offline Points: 6877	Post Options Post Reply Quote Trader Report Post Thanks(0) Quote Reply Posted: Feb/08/2023 at 9:02am
	The parts book has 2 different numbers, one with air conditioning and one without air conditioning. Which does your car have scott? Looks like without. Note: I did find out something in the Special Information - Group 13 70 Series 68-70 prior to sequence # 36090 has a dash panel mount heater control valve and after sequence #36090 it was and intake mounted heater control valve. So with mine being prior to 36090, the dash mount or assume this means firewall should be correct. Edited by Trader - Feb/08/2023 at 9:24am

390ina71jav Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Apprentice Joined: Feb/09/2017 Location: Connecticut Status: Offline Points: 58	Post Options Post Reply Quote 390ina71jav Report Post Thanks(0) Quote Reply Posted: Feb/08/2023 at 11:20am
	Perfect picture. Thank-you. And yes, when you bypass valve cabin gets warm in summer!!!

FSJunkie Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jan/09/2011 Location: Flagstaff, AZ Status: Offline Points: 4742	Post Options Post Reply Quote FSJunkie Report Post Thanks(0) Quote Reply Posted: Feb/10/2023 at 1:02am
	If your heater valve is mounted inside the firewall like the last photo of the yellow car shows, then it is a Ranco thermostatic heater valve. Here is how it works: Air flowing into the car for heating or ventilating always flows through the heater core. There is no bypassing it. The temperature of the air is controlled by the flow rate of engine coolant through the heater core. The heater valve is controlled by a cable over a range from fully shut to fully open, including settings in-between. The point is: the valve is your temperature control device. It's important that you do not hook the hoses up to it backwards. They do not work well with the flow direction reversed. You should also ask yourself "why" the heater valve was bypassed by somebody. Usually, it's because the heater valve leaks. They have a rubber diaphragm inside that leaks coolant when it gets old and rots. Usually that leaking coolant runs down the firewall and soaks the carpet...
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