M20C heater question

[Jcmtl]

My heater is basically useless.  Upon investigation, the scat hose identified as "hot air dump" in the POH, (see attached picture) is missing in my plane.  

Also, with cabin heat full on, I can reach inside that junction box (engine side) and it doesn't seem like anything is preventing the hot air from escaping out from the opening.  

So my question is, is there supposed to be a flap in there that closes off the "hot air dump" if cabin heat is set to full on?  Otherwise, it seems to me like hot air can just escape instead of entering the cabin. 

[ShuRugal]

Yes, the hot air dump should close when cabin heat is applied. There's also one for carb heat. If either of those are missing, I expect you wouldn't get much action on either cabin heat or carb heat.

Sent from my Pixel 3a using Tapatalk

[Ragsf15e]

Also, I think there are two types of valves that people have in there.  Mine has a butterfly valve that opens to allow hot air in incrementally.  I think there’s another type as well.  

What does your heat cable attach to?

[Jcmtl]

10 minutes ago, Ragsf15e said:

Also, I think there are two types of valves that people have in there.  Mine has a butterfly valve that opens to allow hot air in incrementally.  I think there’s another type as well.  

What does your heat cable attach to?

I have no idea.  What are the cabin heat and cabin air knobs supposed to do/ attach to? 

[Ragsf15e]

Well the heat knob attaches to the side of that mixing box in your diagram and moves the valve.  You probably just need to take off your top cowling and look at the connections and maybe inside that mixing box.  It’s pretty simple and I’m no mechanic.  It does need lubed and adjusted from time to time.

[carusoam]

Start at the mixing box on the firewall…

Identify if you have slide gates or butterfly valves…

Slide gates like to be lubed twice each year… get the rust out…

Butterfly valves like to have their rubber seals updated every decade… replace the oxidized rubber…

Dump valves have a tendency to wear, and controls wires bend, break, or slip… update the parts.

 

All fun stuff I learned during my first annual of my M20C…

Lots of non-airworthy items get forgotten/ignored during the annual… because they may not be required.

Heat, carb heat, and outside air can all be improved with these efforts…

Then move to the interior… more to be found there…lots of wear, crumbly rust, and control wire challenges…

Best regards,

-a-

[Rjfanjet]

Replace as much as you can. Makes a world of difference!

[jamesm]

not to state the obvious ..... . I am curious to know condition of the heat muff ?

you have probably already tried this but in my '67C Owner's manual  aka POH pg 26 it says

Defroster System

In order to obtain the maximum flow of heated air through the windshield defroster outlets, the rear cabin, pilot, and co-piiot airflow valves should be closed. With these valves in the closed position, the airflow is forced through the defroster outlets.

When using maximum defrost airflow, the cabin vent control should be in the open position (full aft) to prevent excessively hot air from being directed through the system to the windshield, which could cause windshield deterioriation.

 

Hope this helps,

James '67C

[N201MKTurbo]

My old M20F heater would fry your legs on the coldest days. Like -40 outside. It seems weird that everyone is having heater problems. The heaters aren’t that complicated. 

[N201MKTurbo]

21 minutes ago, jamesm said:

not to state the obvious ..... . I am curious to know condition of the heat muff ?

you have probably already tried this but in my '67C Owner's manual  aka POH pg 26 it says

Defroster System

In order to obtain the maximum flow of heated air through the windshield defroster outlets, the rear cabin, pilot, and co-piiot airflow valves should be closed. With these valves in the closed position, the airflow is forced through the defroster outlets.

When using maximum defrost airflow, the cabin vent control should be in the open position (full aft) to prevent excessively hot air from being directed through the system to the windshield, which could cause windshield deterioriation.

 

Hope this helps,

James '67C

The mooney defroster is weak on a good day. I’ve been iced a few times and with all the defroster that plane has, a 1 inch stripe along the bottom is all you get..

If it is cold and you just have breath vapor on the wind screen, it will make 6 inch vertical stripes above the holes. That’s enough.

[Shadrach]

19 minutes ago, N201MKTurbo said:

My old M20F heater would fry your legs on the coldest days. Like -40 outside. It seems weird that everyone is having heater problems. The heaters aren’t that complicated. 

My 67F has always had a surplus of heat output just as you mention. Not surprising given they are the same design separated by just 10 serial numbers. Do you find the heat output of your J to be equal?

[N201MKTurbo]

32 minutes ago, Shadrach said:

My 67F has always had a surplus of heat output just as you mention. Not surprising given they are the same design separated by just 10 serial numbers. Do you find the heat output of your J to be equal?

My J has the turbo, so it has a totally different heater. Way less effective than what you have. That being said, it does all right, but if it is a -40 day, you better layer up.

[Shiny moose]

My 67F heater puts out massive amounts of heat , I always pull heat knob out and cold air knob, increasing airflow, then i use the cold air knob to mix to get to the perfect temp output 

works perfect