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73 Javelin Heater Core and Heater Control Valve

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CamJam View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CamJam Quote  Post ReplyReply Direct Link To This Post Topic: 73 Javelin Heater Core and Heater Control Valve
    Posted: May/21/2022 at 3:28pm
Took my latest Javelin for a drive today to try out some new tires and got the nice surprise of coolant dripping down from the dash into the passenger footwell. Unhappy

I then found some old threads that said only a/c cars had heater control valves in '73.  
This is the valve that some say is supposed to be correct one:



Mine is an early '73 a/c car and has no heater control valve.  Coolant runs through the core all the time, unless there's something behind the dash that I don't see.  I suppose it's possible that a PO removed the valve, though can't see a reason for doing that.  Is it possible that there was a production change on this in 73?

Next question:  Until I can tear the dash apart to replace the heater core, I plan to put an inline shut off valve in the heater hose.  Not sure which way the water flows, but I was thinking that I should put it on the hose running to the intake manifold since that's where AMC put it.  Or since it's a pressurized system do I need to block both hoses?  I've just coupled the hoses together for the time being. 


Edited by CamJam - May/21/2022 at 4:17pm
'73 Javelin 360 (current project)
'72 Baja Bronze Javelin SST
'69 Big Bad Orange AMX (2018 Teague Heritage Award) SOLD

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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: May/21/2022 at 4:28pm
Going by when I had a 73 for myself... there was one on the passenger side rear corner of the intake. AMC used an angled pipe fitting for 71 and 72, 2nd gen Javelin.

It is possible but, not in the TSM...
If your car is very early, the input and output heater fittings on the firewall would have a plate near by with a dual fitting feed for heater hose. That would be the RANCO heater valve. Easy to notice, without searching for vacuum lines.

On 73 and 74, the heater control panel had a vacuum actuator mounted to control a small vacuum line from a T fitting to the from vacuum switch control at the driver's side (Open/Close lever). You should see a standard size vacuum tubing near the wiper motor, on the firewall, and a smaller vaccum line or hole for one, that is near it. Its been a long time, so its location is vague.

If you see an unused hole or line, it is that the heater control section was removed. Being that your in the sun belt, I find making the heater always on, an unbarable option. Better to have the heater port plugged on the intake.
71 Javelin SST body
390 69 crank, 70 block & heads
NASCAR SB2 rods & pistons
78 Jeep TH400 w/ 2.76 Low
50/50 Ford-AMC Suspension
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Ford Racing 3.25 gears & 9" /w Detroit locker
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CamJam Quote  Post ReplyReply Direct Link To This Post Posted: May/22/2022 at 10:41pm
Ok, this must be what you're talking about.  I have this vacuum canister that looks like the Everco heater control valve in my first post, but it doesn't have a water hose output.  You can just barely see it behind the PCV valve.  The hose to the heater core is to the left of that and comes directly out of the intake manifold.



I also found these two loose vacuum hoses hanging down behind the engine.  I'm guessing that one goes to the vent open/close switch and the other to a heater box flapper door?  



So does that mean water runs through the heater core continuously and only the flapper door keeps the hot air out of the vents?  Sounds a little screwy to me, especially with 50-year old foam seals on the flappers!  I'm guessing some bean counter must have decided that vacuum motors were cheaper than heater valves, or is there perhaps a valve inside the vacuum motor where it threads into the intake manifold?


Edited by CamJam - May/22/2022 at 10:47pm
'73 Javelin 360 (current project)
'72 Baja Bronze Javelin SST
'69 Big Bad Orange AMX (2018 Teague Heritage Award) SOLD

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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: May/23/2022 at 4:43am
Originally posted by CamJam CamJam wrote:

Ok, this must be what you're talking about.  I have this vacuum canister that looks like the Everco heater control valve in my first post, but it doesn't have a water hose output.  You can just barely see it behind the PCV valve.  The hose to the heater core is to the left of that and comes directly out of the intake manifold.



I also found these two loose vacuum hoses hanging down behind the engine.  I'm guessing that one goes to the vent open/close switch and the other to a heater box flapper door?  



So does that mean water runs through the heater core continuously and only the flapper door keeps the hot air out of the vents?  Sounds a little screwy to me, especially with 50-year old foam seals on the flappers!  I'm guessing some bean counter must have decided that vacuum motors were cheaper than heater valves, or is there perhaps a valve inside the vacuum motor where it threads into the intake manifold?




That looks like an early OEM EGR valve, for emissions.

Yes, that free vacuum line and one way valve fits on a fitting behind the carb on the intake. Looks like they removed the T fitting and placed vacuum line directly on the nipple. Its location is pictured near center on 1st image.

Its been a long time, but as I recall, the T fitting laying on its side, has short sections of tubing to allow connection between the valve and intake nipple. The one way valve fits directly over the T. I think the loose vaccum line near the valve is to go to the heater valve. Once the one way valve is in place, the disconnected line can be verified by using the heater controls. Heater in off position will give no vacuum, in other settings vacuum is given. Vacuum vent switch operation may not function until the disconnected vacuum line is returned to the heater valve. So if doing a quick check you can attach your unmounted heater valve, and set the vent to open and heater set, before starting. Once started, you should hear the vent open. As for heater valve, you can then disconnect, to verify diaphragm releases. That is the quickest way to do a check for operation of the vacuum controls.

DLTowers, should have something like that on his 74. Not sure if Billd has his like factory on his 73 with after market dual quads. The bugger is once you have the connections proper, is correcting faults that maybe behind the center pod.

Actually the vacuum feeds the vent open switch and a vacuum switch from a T fitting behind the cluster pod. The heater valve switch is also behind the pod.

I do note, there is an interesting looking raised mounting arm, on the head... none of my 73 and 71 cars had one, installed.

As for operation, no different than prior setup, just vacuum operation and at the engine, not on firewall. Modernized mostly. Once you see its simplicity the only issue with them is failing diaphragm and vacuum lines. Being 50 years old, you may want to replace them, while you are at this point.

Edited by 304-dude - May/23/2022 at 5:25am
71 Javelin SST body
390 69 crank, 70 block & heads
NASCAR SB2 rods & pistons
78 Jeep TH400 w/ 2.76 Low
50/50 Ford-AMC Suspension
79 F150 rear & 8.8 axles
Ford Racing 3.25 gears & 9" /w Detroit locker
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mopar_guy Quote  Post ReplyReply Direct Link To This Post Posted: May/23/2022 at 5:14am
Does it have the setup like this on the firewall?


I'm guessing you do which is the Ranco valve. You unhook the 2 hoses from it and the screws that hold it to the firewall and it pulls out. It could possibly be the leak as well.

"Hemilina" My 1973, 5.7 Hemi swapped Javelin
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kirkwood Quote  Post ReplyReply Direct Link To This Post Posted: May/23/2022 at 6:35am
I have two 1973 AC cars and both have that valve, as far as I know all air conditioned cars in 1973 had it. Of course, if it’s leaking under the dash The valve would simply shut off the flow to the heater core.

The redesigned heater box was a big feature for 73, so it sounds like you need this valve.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lefthanded Quote  Post ReplyReply Direct Link To This Post Posted: May/23/2022 at 7:13am
I have a question about the AC. Did you convert over to R134 Freon? I am reconditioning all my lines and dryer. Have not decided to go with the R134 or stay with the R12. Which way did you go and are you happy with it?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CamJam Quote  Post ReplyReply Direct Link To This Post Posted: May/23/2022 at 2:14pm

Here's my firewall.  No valve of any sort.  This is an a/c car.  The setup Mopar-guy posted above looks like the one in my '72, but this '73 (made in Aug 72) is different.

So is the consensus that the vacuum motor at the rear of my engine is for emissions control and has nothing to do with the heater?

So where is heater control valve?






This sounds like BillD's car, but his was non-a/c!  When I move the "heater temp" lever on the Weather Eye a cable moves a flapper in the heater box, so water must be running through the core at all times.  Don't know yet if there is a vacuum operated switch behind the dash (see Pit Crew's post in BillD's thread below) but if so, there would still have to be a heater control valve somewhere.



Edited by CamJam - May/23/2022 at 2:49pm
'73 Javelin 360 (current project)
'72 Baja Bronze Javelin SST
'69 Big Bad Orange AMX (2018 Teague Heritage Award) SOLD

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Post Options Post Options   Thanks (0) Thanks(0)   Quote kirkwood Quote  Post ReplyReply Direct Link To This Post Posted: May/23/2022 at 2:48pm
The 71-72 use the firewall mounted valve. The 73 uses the valve you pictured, screwed into the intake port. You can see the water valve in this photo, just to the right of the middle. If yours went bad and they couldn't find a replacement they likely put a pipe fitting in the intake and eliminated it, routing the hose to the heater core for an "always on" situation. The heat valve is actuated by a vacuum switch on the heater box.

There is a second valve more in the middle of the intake, held on with two cap screws; that is the EGR valve. The heat valve is threaded into the intake.



Edited by kirkwood - May/23/2022 at 2:53pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mopar_guy Quote  Post ReplyReply Direct Link To This Post Posted: May/23/2022 at 2:55pm
My 73 wasn't an air car and it had no vacuum valve on the intake. Isn't that just for air cars?

"Hemilina" My 1973, 5.7 Hemi swapped Javelin
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