The Stovebolt Site Forums The Shop Area Interiors Fresh air heater question: Defrost vent flap

My question: Which direction does the lever move for "defrost"? Right or left?

I just installed an original one this spring and haven't hooked up the defroster cable, generally I keep it on defrost as its always humid here. This summer though I threw the valve open to get the cool air on the floor, without thinking much of it.

Now I need defrost again in the mornings. There is a sticky point with it I had to push it past; and now whether I move the lever forward or back, I can't see much of anything for air coming out of the defrost ducts. Putting some light paper over the defrost ducts didn't make any noticeable difference just now. Yes the vents are hooked up at both ends! I put a pen up inside and can feel the flap moving with the lever, so that's technically working.

So I'm asking this question to make sure I'm messing around with it in the right direction to start.

Thanks!!!

Can you feel air blowing out the bottom when it's on heat? If not, maybe you have your fan installed on the shaft backwards/upside down pitching the blades in the wrong direction.

Yes the air blasts out the bottom like a super charger. It did a decent job of cooling the cab this summer.

Interesting. Then you know which way is heat. I have no explanation for why you don't feel anything coming from the cowl vents. I don't think it blasts out of there but turn the heat on and see if you at least feel hot air coming through the vents.

I can feel hot air coming out but it remains unchanged regardless of where the flap lever is. And to that end it actually does (slowly) defrost the windows (again, regardless of where that lever is), but the air volume does not change (and like I say, it barely moves a piece of paper). That's why I'd like to know for sure what direction the lever is supposed to move. Then at least I can try and manipulate that flap a little more in the correct direction, I'm guessing it's caught on something and not travelling enough.

That floor vent, works great (again, doesn't change at all as the lever is moved) - I may try physically blocking that vent off and see if I can foce that air up onto the windows. I don't really want to pull that heater box out again to see what's going on with the flapper but obviously at some point, that'll have to happen.

Is the defrost output tube plugged with anything? Try pulling hoses off to see if you get air to the place you hook up vent tubing.

Chris

I was going to pull it off and have a look, if only to try and push or pull that flapper valve; it's all brand new so "shouldn't be" - but never say never.

I really think it's the flap as it is sticky; believe it isn't travelling far enough (and that's why I want to know what direction is which)

Best option is always eyes on it when in doubt. Let us know what you find!

In answering another Bolters question about a "defrost cable" I think I stumbled across the answer to your question.

Below is an enlarged section (rotated on it's side to better show the normal position of the heater/defroster control) of one of the pics I posted in that thread (from a 1950 Accessory Manual) that looks like it displays the cable/control and internal "flap" positions.

Looks like when the control knob is pushed in with the control arm in about the 5 o'clock position, the damper flap is "closed" (pushed up to seal off the duct openings). Pulling the control knob/cable out should move the control arm to about the 7 o'clock position and pull the damper flap down, opening the entry port for the defroster feed tubes. If I am reading the diagram correctly???

If you have very restricted air flow to the defrosters, it's possible that damper flap is stuck in the closed position and the control rod shaft is just spinning in the damper flap hole.

Unfortunately sounds like you are going to have to do some disassembly to further diagnose the problem and find a solution.

Come back and let us know what you find out and a fix if you are able.

Dan

Much obliged Gdads51. I can confirm that is the correct answer.

This morning I found out that the flapper is spot welded on and had actually popped off; it was kind of reacting to the lever moving around but was otherwise stuck in that forward position and effectively blocking off the defrost ducts. I put a hook tool in there and gave it a decent pull (but the tool was pretty light so it wasn't an abusive tug) and it fell on the floor

However, I blocked off the floor vent and PRESTO all the air now goes through my defrost vents. So although I can't switch back and forth with a cable, that'll work fine for fall up here I'll fix that at a later date.

Good to hear that "the culprit" (loved the picture caption ) has been found and you have the knowledge to get it fixed!

Have a great one!

Dan