1982 911SC - Can't get heat to stop

[redstormcoach]

I can't seem to stop the heat coming into the cabin. The problem is only on the passenger side abd the heat comes form the footwell and some form the defrost vents. Driver side has no problems. Both Defrost levers are down. I read about stuck flapper boxes and I jacked up the car today and saw the flapper box vents were open (that means flap is closed and no heat should be coming in, correct?) I did look under and behind glove compartment and the small hose was split and basically crumbled in my hands. The larger one has a small crack in it at well. Could this be the culprit?

Anyway I sprayed some lubricant and moved the flap by hand left and right a couple of times to open and shut the vent. No change. Heat is so hot that nobody can sit in that seat. I am in Maine now but shipping the car to CA soon and I dont want to roast out there.

Anybody have any ideas?

Thanks
Jay

[Tidybuoy]

I just had (and fixed) the same problem; my heat was stuck on.

Even if the flapper box vents are open, they must be partially closed or you wouldn't have heat - it's the only way heat can get in.

On my car, the flapper boxes were working properly but the cables were not. Each cable has a plastic sheath which the cable travels thru. The ends of these plastic tubes have a fitting that the plastic tube fits into. This fitting was loose on my car and so when you pulled the heat leaver up, the cable would tighten but when you turned off the heat, the ends would move and get hung up (preventing the flappers from completely closing). My flapper box was only sticking open about a quarter inch and that was enough to burn my toes.

To fix this, I disconnected the heat cables at the flapper boxes and pulled the plastic tube sheath off. two of the fittings were near broken so I cut clean ends on the plastic tube and then worked at cleaning out the fittings. Once the fittings are perfectly clean, you can insert the plastic tube and it will grip (it's a one-way fitting so once on, it wont pull off).

While I was at it, I removed the flapper boxes and painted them.

After assembling, the heat finally shut off. Took about 4 hours and it's kind of a pain but I'm glad I did it.

Hope this helps.....Vern

[redstormcoach]

I understand that but being that I forceably opened the vents (closed the flapper) heat wouldnt be able to get into the cabin? the vents no line up with the opening and they are 100% open. I was also thinking that the flap itself inside the box has deteriorated and there is a hole in it allowing heat to pass through it.

[Tidybuoy]

It's possible that the inside of the flapper has deteriorated. I'm not sure if you can see in there without removing from the car. There is a teflon type seal inside the flapper box that is supposed to seal out all heat when the flap is closed.

Good luck.

[Flat Six]

Originally Posted by Tidybuoy

It's possible that the inside of the flapper has deteriorated. I'm not sure if you can see in there without removing from the car. There is a teflon type seal inside the flapper box that is supposed to seal out all heat when the flap is closed.

Good luck.

+1

See here:

Cleaning Flapper Boxes

[Carl83911]

as a temporary measure, you can unplug the harness from the blower motor until you find where the problem lies regarding the flappers and levers that control the flow.

[Vincent Hill]

Originally Posted by Tidybuoy

I just had (and fixed) the same problem; my heat was stuck on.

Even if the flapper box vents are open, they must be partially closed or you wouldn't have heat - it's the only way heat can get in.

On my car, the flapper boxes were working properly but the cables were not. Each cable has a plastic sheath which the cable travels thru. The ends of these plastic tubes have a fitting that the plastic tube fits into. This fitting was loose on my car and so when you pulled the heat leaver up, the cable would tighten but when you turned off the heat, the ends would move and get hung up (preventing the flappers from completely closing). My flapper box was only sticking open about a quarter inch and that was enough to burn my toes.

To fix this, I disconnected the heat cables at the flapper boxes and pulled the plastic tube sheath off. two of the fittings were near broken so I cut clean ends on the plastic tube and then worked at cleaning out the fittings. Once the fittings are perfectly clean, you can insert the plastic tube and it will grip (it's a one-way fitting so once on, it wont pull off).

While I was at it, I removed the flapper boxes and painted them.

After assembling, the heat finally shut off. Took about 4 hours and it's kind of a pain but I'm glad I did it.

Hope this helps.....Vern

I just saw the inside of the heater boxes and saw they’ve got the Flapper Valves you mentioned! Now to get mine to work properly! Thank you for posting your knowledge because it was sure Needed

For the First time (And Living in Florida made it worse, I also had Heat Come into the Cabin and almost burn my feet! I had to shift the air to the Dash to survive!

You mentioned “Flapper” valves?? As far as I know, the Cables for Heat are attached to a heater box on both sides that have Rotary Valves that either let the Heat blow straight down behind the rear wheels or directed to the Cabin. Mine are both “Open”

So where are these “Flapper” Valves and how are they attached to the heater levers by the Emergency Brake levers. Any Pictures would be Greatly appreciated

[pete3799]

[MichaelSJackson]

+1^^ Pete's photo has a better angle than the shot I was posting.

Our host carries these.

https://www.pelicanparts.com/More_Info/90121100722.htm?pn=901-211-007-22-M124

You can see the triangular holes that allow heat/air to spill out when closed. More importantly, inside, on the same pivot is a round door that controls the flow to the cabin. That door must be completely closed to prevent heat getting into the cabin.

I was able to take mine off and refurbish them. Otherwise, there are several slightly different models on the website to chose from.

[Vincent Hill]

Originally Posted by MichaelSJackson

+1^^ Pete's photo has a better angle than the shot I was posting.

Our host carries these.

https://www.pelicanparts.com/More_Info/90121100722.htm?pn=901-211-007-22-M124

You can see the triangular holes that allow heat/air to spill out when closed. More importantly, inside, on the same pivot is a round door that controls the flow to the cabin. That door must be completely closed to prevent heat getting into the cabin.

I was able to take mine off and refurbish them. Otherwise, there are several slightly different models on the website to chose from.

THANK YOU for your Instant reply. I plan to use my Borescope and take a Look. My car is Covered but sits outside and I think “Something” may have gotten in to stop the Valve from closing. I have owned this car for about 15 years and this never happened before or in the 1976 we had. Glad you are keeping up on people replying to your thread and Thank you again👍🏾👍🏾

[7783911]

I agree with TidyBuoy...make sure no binding of cables and that the spring is firm to close the flap. If still and issue, then yes, the flap is probably the culprit, doesnt take much opening to get heat. But you fan should not be on if the levers are down, so check that switch too or run a separate manual switch to the motor. I removed my motor (heat backdate) and get plenty of heat when needed without it

good luck..pm me if you have questions

[Vincent Hill]

Originally Posted by 7783911

I agree with TidyBuoy...make sure no binding of cables and that the spring is firm to close the flap. If still and issue, then yes, the flap is probably the culprit, doesnt take much opening to get heat. But you fan should not be on if the levers are down, so check that switch too or run a separate manual switch to the motor. I removed my motor (heat backdate) and get plenty of heat when needed without it

good luck..pm me if you have questions

FINALLY finished the Valve adjustment and checking over the engine and Oil Change (went to Vavoline VR1 Full Synthetic with High Zinc 20w/50. A crazy Blue color)

The boxes are almost 100% closed. Sprayed them with PB BLASTER and the springs “Look” Rusty and weak. So after I give the penetration oil a little time to work, will go back out and work with levers and do a little prying and see what k have and take a few Pics to post. I am Happy that at least I can now “SEE” the problem! Here this car is an 82 and my 1976 NEVER Had this problem! The 76 had close the to 300,000 miles before it was Wrecked at 130 MPH. This one only 140,000. So I wonder what is the Difference?

[Vincent Hill]

Resolved my issues! Turned out after spraying PB Blaster and cleaned up everything, I need “New return Springs! They are weak and rusty