Cabin heat stuck on, how to adjust?

[Ragsf15e]

I have a 1968 F model and the cabin heat is always on at least a little.  It does adjust with the control in the cabin, just never completely shuts off.   It's nice in the winter, but it's getting a bit warm as the weather warms up!  

I'd like to know the right way to adjust it.  I poked around in the engine compartment and I see where the heater control rod from the cabin moves a lever back and forth on a metal box connected to the firewall.  It looks like there's a way to loosen the nut holding the rod to the lever, adjust it and retighten (cotter pin on there too).  

Is this the correct place to adjust that or do I need to open up something else?

thanks!

[Yetti]

Seems like a good plan.  Lube the cable, make sure everything is free and moves stop to stop.

Just a PPC holder

[carusoam]

The slide gate air valves are (probably) under the cowl, on the copilot side. Lube the gates, they slide pretty easily.  This is an annual event.  If you don't lube the gates, they stop working a year later...

One gate is for hot air, the other gate is for cold air.

Fuzzy Memories from a 65C...

Best regards,

-a-

[N201MKTurbo]

Take the hoses off the air box on the firewall and look inside, it will be very obvious how it works. The round rubber seals may have fallen off.

[carusoam]

What year did they go from slide gates to round throttle plate like devices?

Somebody had posted pictures (recently) of the round ones as they found the parts had come loose...

hope that may help.

Best regards,

-a-

[N201MKTurbo]

I'm not sure, My 67F had the round valve on an arm and my 77J has the slide. I like the round valve better the slide is cheaper.

[Ragsf15e]

Thanks. Looks like I've got a round valve on an arm.  Hoping i just adjust the end stop as the cable slides freely over it's entire throw. Thanks for the insight!

[carusoam]

The round valve is a smaller piece of metal over a round disc of rubber. If the rubber has aged and broken, it could be the source of not blocking off completely...

Best regards,

-a-

[N201MKTurbo]

FWIW,

There is always airflow through the heater muff when the plane is moving. The hot air either flows through the hose to nowhere in the engine compartment, or into the cabin. When you open the heater valve part way it allows some of the hot air into the cabin, when you open the heater valve all the way it blocks the hose to nowhere and forces all the hot air into the cabin.

The later models with the slide don't have the hose to nowhere, they just have a vent port on the side of the slide assembly.

Edited April 25, 2016 by N201MKTurbo