Disconnect Heater/67 GTX

[FlagCraig]

I have A/C on the 67 GTX which I never use nor do I use heater.
Was driving it this weekend and noticed heat coming out like I had fan on. No fan on and off button was pushed in with temp lever all the way to left (cooler).
I pushed other buttons just to see and still heat.

What is the easiest way to disconnect heat (blower/fan) so I don't have to worry about it right now?

Will look more serious at issue in winter.

Thanks.

 

[khryslerkid]

I'm thinking that air coming through the cowling, though the box, across the core, will bring it into the cab. Especially if the door in the heater box isn't operating or sealing real good. That's why ac cars will have a valve on the heater hose. I've placed a shut off valve, inline, on them myself. I'd open them periodically to let the coolant circulate. Check the operation and seal on the door in the box and the control valve on the heater hose if it has one.

 

[texas69bee]

I'm not so sure about this generation of cars but on much newer ones when the resistor goes bad the blower motor will keep running. If it's set up like a 69, disconnect the wires you see on the front side of the heater box. Khryslerkids options are a real good possibility as well.

 

[67GTX440]

I have A/C on the 67 GTX which I never use nor do I use heater.
Was driving it this weekend and noticed heat coming out like I had fan on. No fan on and off button was pushed in with temp lever all the way to left (cooler).
I pushed other buttons just to see and still heat.

What is the easiest way to disconnect heat (blower/fan) so I don't have to worry about it right now?

Will look more serious at issue in winter.

Thanks.

It sounds like your heater bypass valve may have failed. It is operated manually from the temp control lever on your dash. If you remove the cardboard in your gloved box, you can see it move back and forth when you move the control lever. If the blower fan is not really running, disconnecting it is not really an issue. If the switch is off, the fan should not be running.

Your heat and AC controls are vacuum operated and run off a vacuum line that connects into a fitting on the back of your intake manifold. The small diameter line runs to your heat and AC controls and the large one runs to your power brake booster (if the car has power brakes). Check to see that this line is not split, cracked or disconnected.

You can always pull the heater hoses and cap them at the firewall and where they go into the engine block above the water pump. Auto parts stores have caps and clamps for the engine block end and the firewall end just need push on caps to keep out any foreign matter as it is not under pressure. Any coolant in the heater core will remain there, but will not circulate or be heated.

Is your left air vent open and could it be the source of the hot air? On a hot day at speed it feels like the heat is on, whereas the air through the windows seems cooler.

Does your AC work? The AC system needs to be run occasionally both summer and winter to maintain the seals. Keep in mind that an AC system and heater core that are not used are continually deteriorating, particularly when someone removes AC components and leaves the system open to contaminants. Rebuilding the under dash unit is not easy and costly. Replacing the under hood components is the same. That is why you see so many cars for sale advertised as factory AC cars where the under hood components are missing. AC systems intact but not working in cars for sale are often advertised as "just needing a charge." This really means it will take about 2K to get the AC working again if you can find someone willing to do the work in the event you do not know AC.

An AC car generally brings a 5% price premium in the price guides the same as a 4 speed car. It is worthwhile to keep it working and enjoy it on hot days.

 

[texas69bee]

Lots of good info!

 

[FlagCraig]

Good stuff 67GTX440. I haven't really tested the A/C other than when I bought it. I'm going home tonight and do it. Thx.

 

[Jeremiah]

I agree on the heater valve being stuck open. The original valves would get stuck and cause a few symptoms, one of which you are experiencing.

A few questions:

1) Even with the "OFF" switch depressed can you still hear the blower motor blowing?
2) Can you feel any resistance on the temperature control lever? Could it be stuck on hot and just flexing the cable when you move the lever to cold?
3) Do you have a service manual? A quick read through the A/C section would save me a ton of typing!

Overall, there four functions of this era Chrysler A/C system. DEF, HEAT, A/C, and MAX A/C all use different trap doors in the air box and two coolant flow control valves. The first valve, located on the firewall is the heater bypass valve. If the system gets to hot the bypass valve opens to keep water from circulating into the system at the firewall. The second valve is the temperature control, or "h" valve. This valve is hooked to the cold-hot lever and controls the occupants' comfort by limiting the coolant running through the heater core therefore controlling the temperature.

In my experience the dash controls, h valve, and bypass valve will need to be repaired or replaced. The dash control is available as a superseded part number (another topic in itself), a similar h-valve can be used after slight modification, and a rebuild kit is available for the bypass valve. Once you have these three things under control things get much better. Also, Detroit Muscle Technologies sells a really nice kit to restore your heater box with all of the gaskets, etc.

I'll attach a few picture for inspiration if you decide to pull it apart.

 

[terzmo]

I installed a 5/8 by 1.5 inch steel slug inside the hose at the firewall and clamped the slug so not to pass water and siliconed the inside of the hose to connect on the heater core. The slug has to be pushed in the hose enough to allow the firewall connection. It looks fine and no one knows I defeated the heater

 

[dan juhasz]

I agree on the heater valve being stuck open. The original valves would get stuck and cause a few symptoms, one of which you are experiencing.

A few questions:

1) Even with the "OFF" switch depressed can you still hear the blower motor blowing?
2) Can you feel any resistance on the temperature control lever? Could it be stuck on hot and just flexing the cable when you move the lever to cold?
3) Do you have a service manual? A quick read through the A/C section would save me a ton of typing!

Overall, there four functions of this era Chrysler A/C system. DEF, HEAT, A/C, and MAX A/C all use different trap doors in the air box and two coolant flow control valves. The first valve, located on the firewall is the heater bypass valve. If the system gets to hot the bypass valve opens to keep water from circulating into the system at the firewall. The second valve is the temperature control, or "h" valve. This valve is hooked to the cold-hot lever and controls the occupants' comfort by limiting the coolant running through the heater core therefore controlling the temperature.

In my experience the dash controls, h valve, and bypass valve will need to be repaired or replaced. The dash control is available as a superseded part number (another topic in itself), a similar h-valve can be used after slight modification, and a rebuild kit is available for the bypass valve. Once you have these three things under control things get much better. Also, Detroit Muscle Technologies sells a really nice kit to restore your heater box with all of the gaskets, etc.

I'll attach a few picture for inspiration if you decide to pull it apart.

I'm dealing with a situation now with my 67 gtx with factory air. The bypass and H valves aren't they one in same component at the firewall. My issue is no circulation through the heater core. I started to disassemble under dash. I can see the cable (hot cold) physically move back and forth but I don't think it actually does anything inside. Not sure how to proceed as I don't see any one that sells or rebuilds these valves. Any ideas?

 

[67GTX440]

I'm dealing with a situation now with my 67 gtx with factory air. The bypass and H valves aren't they one in same component at the firewall. My issue is no circulation through the heater core. I started to disassemble under dash. I can see the cable (hot cold) physically move back and forth but I don't think it actually does anything inside. Not sure how to proceed as I don't see any one that sells or rebuilds these valves. Any ideas?

https://originalair.com/restoration-mopar-heater-valves