Cabin Air Hot!

[0TreeLemur]

When I pull the "Cabin Air" knob in our "new" J, the air comes out hot.   Not warm.  Hot.  What's up wit dat?   I thought it was just a scat hose direct to the NACA duct in front of the cabin door?   Anyone dealt with this before?

Edited February 15, 2023 by 0TreeLemur
clarity

[haymak3r]

Not sure I understand. Cabin heat comes directly from the exhaust shroud. And yes, in flight, if I put my hand down by the vent it is pretty hot. my fuel selector also is pretty hot to touch too as it is right in front of the vent.

[0TreeLemur]

2 minutes ago, haymak3r said:

Not sure I understand. Cabin heat comes directly from the exhaust shroud. And yes, in flight, if I put my hand down by the vent it is pretty hot. my fuel selector also is pretty hot to touch too as it is right in front of the vent.

Not the "Cabin Heat" knob, I'm talking about the "Cabin Air" knob, which should not cause hot air to enter the cabin.

[hammdo]

Unless someone reversed the hoses ;o)

-Don

[mcarterak]

I wonder if someone rigged either the hoses or the blend door cables wrong. Drop your cowlings and check it out. It's pretty evident which connects to which. 

[AIREMATT]

I thought they both went into the same mixing box on front side of firewall. Did they get worked on and hooked up backwards?

[Guest]

From the IPC 

[PT20J]

That's not right. I would trace the connections and compare the the drawings that Clarence posted.

[0TreeLemur]

It's a mystery.  The temperature of the air is essentially the same whether I pull "Cabin Air" or "Cabin Heat".   Flow rate is more/less the same too.   Looking at the drawings from the IPC above, it seems that two things must be wrong to see that behavior.   Disconnect the scat hose (35)  from the NACA inlet to the mixing box, and no air should come out.

I know hose (50) from the muffler shroud to that hot air control box is connected.   Plenty of hot air when I pull "Cabin Heat".

Hmmm.

[N201MKTurbo]

Probably the hot air valve in the mixing box is messed up. There were a lot of different arrangements. Fixing it is not rocket science. Just take the big hoses off on the engine side of the firewall and see what is happening. You will figure it out.

[0TreeLemur]

1 hour ago, N201MKTurbo said:

Probably the hot air valve in the mixing box is messed up. There were a lot of different arrangements. Fixing it is not rocket science. Just take the big hoses off on the engine side of the firewall and see what is happening. You will figure it out.

To be clear, you're saying that if I take the hoses off the engine side of the firewall, I can view what's happening in the mixing box?  WRT the figures, is (17) the mixing box?   I've seen it, it lives in front of the front wheel well.  

I've got time.  But, gotta solve this before the 'bama summer heat index gets crankin'

Thx.

Fred

[EricJ]

17 minutes ago, 0TreeLemur said:

To be clear, you're saying that if I take the hoses off the engine side of the firewall, I can view what's happening in the mixing box?  WRT the figures, is (17) the mixing box?   I've seen it, it lives in front of the front wheel well.  

I've got time.  But, gotta solve this before the 'bama summer heat index gets crankin'

Thx.

Fred

Yes, 17 is the mixing box.   With the cowl off you can see the scat tubes where the hot and cold air come in, and cables 27 and 32 control the Cabin Air and Cabin Heat.   Something may be stuck.   If you open it up take the time to lube the cables and the slides for the gates.    It makes a big difference in ease of operation.