Puzzled

[ingramlee]

Hi Folks,

 

I have a 73 non tii that I've owned now for 7 years. The heat from my floor area works really well and gets nice and toasty, however no matter what I do, the windshield defroster always blows cool air even when I close off the valve. I get that the valve may be broken but why is the air always cool. Isn't the floor and defroster both fed from the same heat source? THX

[02Pilot]

Yes, same heat source. I think the primary difference is that the floor ducts come straight from the heater box, while the defrost vests have long ducts running along the upper firewall feeding them. The same upper firewall that is largely insulated from engine bay heat by the fresh air intake trough. Cold ambient air flowing through that in close proximity to the long ducts gives air traveling that route plenty of time and opportunity to cool off.

[Guy Cocquyt]

I have the same problem on my 1970 carburetor model. I am getting under the dash soon to investigate and definitely am interested in the advice you get.

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[02Les]

Make sure ds & pass side vent hoses are connected both ends, & there are no restrictive kinks in the vent hoses.

Edited February 28, 2019 by 02Les

[Healey3000]

Perhaps the fresh air flap is stuck in the fresh position.  Since the defrost ducts are closer to it, they may get a direct blast of outside air while the floor ducts may be getting a mix of hot and cold.

 

The fresh air flap is supposed to move with the temperature lever, that is, both the flap and valve move in concert.  Maybe one Bowden cable is broken or stuck.

[ingramlee]

Healey3000 you may be onto something. Even when I move the lever there is no change to the airflow for the defroster. It always blows air, albeit cool air no mater the position of the lever. The saga continues. I will dig deeper tonight after work. Thanks...

[Guy Cocquyt]

Do you have the single slide lever for heat on the right?  If so, it has 2 wires attached, one opens and closes the brass value to allow hot coolant into the heater box radiator and the other wire closes the flap that allows fresh air in.  The wire to the flap has a coiled end which is a press on fitting  which could have popped off if the hinge on the flap became too stiff (e.g. rusted).  

 

 

 

 

[ingramlee]

I have 2 levers on the right side of the dash and 2 on the left side. One on the right is for heat the other is for the fan. One on the left controls the flaps for the footwells the other one I think is for the flaps for the defroster but that one doesn't work.

[Guy Cocquyt]

If you don't hear or see anything happening when you slide the lever to defrost, it probably is detached either at the lever or inside the heater box. I suggest checking the lever connection first and pray that is where the problem lies and not in the box.

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[ingramlee]

Yeah... I just need to get under there a tear into it. I just figured since the floor heat works so well that the defroster would put off some heat instead of being continuous cool air, but it doesn't even blow warm air.