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mikey70

No Cabin Heat-SOLVED!

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The problem of no cabin heat has been well documented here and as suggested, I covered the cabin openings with foam blocks which did indeed reduce the air infiltration, however I still wasn't getting any heat. I checked the butterfly valve on the firewall and it was working correctly. When I inspected the air plenum that feeds the heat shroud I noticed that the rubber gasket on the front is made up of individual pieces of rubber and not the one piece that is shown in the parts manual. When installing the bottom cowling, the bottom piece of rubber will more than likely position itself so as to block the airflow into the heat shroud. No air flow = no heat. Its easy enough to tuck this rubber piece under the cowl opening after the cowl is fastened and that fixed the problem of no heat. The guy I bought the airplane from did not know about it either. He said the heater did not work. I believe this could also lead to a lack of carburetor heat as well so its more than just creature comfort. 

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Have you tested it since the repair? I have 4 CTLS's and the problem is the same in all of them. I have blocked all of the places where air can come in an that did stop the breezes but still not heat. I have changed the rubber piece and made sure they are in place. Still no heat. The latest thing I did was buy a small smoke machine and blew smoke into the intake. I found a massive amount of leaks around the heat shield that goes around the muffler. I sealed that with RTV and still the heat is not acceptable. Even when using the smoke I can't get the smoke to come through the heat diffusers in any great amount. The valve is working properly. The heating system just does not work. I have seen where others have said they can fly in a tshirt but I think they have CTSW's. 

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For the CTSW the rubber flap being out of place will not effect the carb heat.

Al, my experience was that the heat worked OK, but I am further South, and likely not trying to fly in as cold weather as you. The other thing is the valve doesn't need to be just working. it needs to be working perfectly. It has to go to the extremes of full open and closed. You might also try removing the diffusers. With them installed there may be to much restriction to the airflow, causing more of the heat to be pushed up to the cold windshield where it cools to quickly to do any good. 

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I have flown since I put the flap back in place and it is much better. With OAT at 40 F I had the heat valve about 1/3 open and was comfortable in a light jacket. In my case the plumbing was all ok, I just wasn't getting any airflow INTO the heat shroud. In my case, I was not feeling any air coming in to the floor vents or windshield. Perhaps you have already tried this, but you might be able to pinpoint where the restriction is by disconnecting the duct hose at the firewall heat valve and push the smoke through just the heat shroud. If that works ok then inject the smoke right at the heat valve and  see how that works. 

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I flew to Denver a couple weeks ago with my wife and nearly froze some of her parts off. The outside air temp over Wolf Creek Pass was in the teens. the cockpit temperature couldn't have been much warmer as, all of the sudden, the heater was not providing its usual warming for the sides of our ankles closest to the pedestal.

Incidents like this make it ever harder to get my wife to go with me.

So when we I got home, I took a close look at it. The diverter plate in the heater valve box (officially called the "cabin heater choke") was only swinging forward a tiny bit from the closed position. Long story short; one of the fasteners that hold the box in place had loosened enough that the head was standing proud from the bottom of the box. The edge of the diverter plate was catching on it. I could have saved a lot of work by just sticking a small Allen wrench down into the box and tightening it, instead of taking the whole thing apart.

Keep this in mind if you suspect you may have the same problem.

Mike Koerner

 

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How to fly in short sleeves when it's single digits outside. Finding and fixing heat issues and making the cabin cold air free.

Start at the front. The lower air duct opening for the heated air should align with the opening. If it doesn't loosen the two clamps on the muffler and move the duct to a more aligned position. This is usually up more. Make sure when the cowl is on that the rubber baffling around the duct is not in the way of the opening. When you did a hose change the 1 3/4" heater hose should have been replaced because these can get vibration holes and split. Next make sure when you pull the cabin heat knob the trap door in the engine compartment in the air diverter opens and closes fully. If not just adjust the cable. Next remove the center instrument panel and make sure the hose inside for the heat ducting is connected and that the heated air duct that comes out the side of the lower panel by your feet is properly lined up with the opening. I see many halfway blocked due to poor alignment. Next use some clear 3" tape and place this over the openings up by your head on each side of the fuselage. and this includes the fuel sight tube opening. If you block up only one or two air just gets forced out the other. Then take some soft foam and cut it into a "C" or an "O" and put it around the metal spar pins up in the spar box. Plug the front and back of the pin opening. Next go to Home Depot or Ace Aviation and gets some 3/8" soft foam with a sticky tape back. This will go around the door edges. It goes all the way around the out side of the door seal on each door. make sure your doors do not have a big air gap up at the front edge. You can either add a little extra foam or just remove the door and relocate the hinges about 1/8" - 3/16" forward and the door will never leak again.

Now your air flow is correct and aligned and the cabin sealed from cold air intrusion and it wall be nice a warm. I can fly easily in the single digits with nothing more than a tee-shirt with good cabin heat. Most of the time it's only open half way. 

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I have been flying the Sierra in winter in Tshirts since my Rotax 503 powered Ultra Light like design in the 1990s.  It works well if you have the plumbing hooked up right and enough air leaks plugged.

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Roger, I have tried to align the intake on the shroud a number of times, but the exit at the aft of the shroud keeps it from aligning. Any hints?

 I am pondering widening the flexible “seal” around the outside of the intake.

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Hi Doug,

I haven't had one I couldn't slide up as far as the radiator which should be plenty far. Try and adjust or flatten the hose on top of the muffler.

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