Continuous hot air through *one side* of defroster

Folks,
I have hot air coming in continuously through the defroster vents on the right side only, regardless of where I set the air-flow knob or whether I have the heater-lever pulled up. Also, I am getting very little flow through the left side of the defroster even when I try to open it up fully. Under-dash heat works fine.
Any suggestions?
Thanks,
Tobin
1972 911e

Pull off the fibreboard blower/vent cover in the trunk, and check the hoses and valve cables and mechanisms to the defrost vents. I suspect something has detached or broken there, if your heat to the lower outlets is working fine on both sides.

If all looks well at the front airbox, check the heater slides and hoses back at the heat exchangers to make sure both sides are opening and closing properly and the hoses are not torn or detached.

Good luck,
Chris C.

Rusty, frozen heater boxes.

The reason it's only on one side is because your whole heating system is split into two pieces (right and left) with one chain of components (heat exchangers, ducts, heater boxes) servicing each half of the car. So if the passenger-side box has gotten stuck in the open position, you'll have a constant flow of engine-heated air on one side. The hot air is propelled by a blower in the engine compartment, not the fan that controls the velocity of fresh air from the vent under the windshield.

A quick patch for your problem is to lift up the carpet in the passenger's foot well, and unscrew the hose clamp that connects the flexible ducting to the sheet metal tube right on the right side of the foot well. Slide a piece of 4-inch square cardboard in there, and let the pressure from the flexible ductinghold it in place. Put the carpet back, and no more hot air flow. Of course, the downside to this is that there's no heat or defrost at all on that side, now. But it beats cooking non-stop if you're in a warm part of the country.

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Jack Olsen
1973 911 T sunroof coupe

[This message has been edited by JackOlsen (edited 10-14-2000).]

I posted a few days an unusual experience with a 1973 911T left window defrost problem. It blew just a whisp of air compared to the right vent. Last week as I was driving I saw a small piece of what I thought was cardboard sticking out of the vent. My frist thought was that the dash was peeling! I pulled the cardboard and it turned out to be a 1976 parking ticket about the size of two matchbooks. After I pulled it out the vent defrosting was normal. Can't say you have a piece of something blocking your vent but I sure would try a strong vacuum cleaner with one of those narrow attachments and maybe some previous owner had something swallowed by that vent years ago. It could be the culprit. Good lUck.

BR
1973 911T

The continuous heat is due to a heater box( attached to the heat exchanger) that does not close properly.Try to adjust or most likely replace;the heater box flaps have plastic surrounds that become deformed with old age. The problem with the amount of air is independent. The air distribution system consists of separate levers, wires and flaps which in your case must need adjustment or fixing.




[This message has been edited by Renos (edited 10-14-2000).]

I have a 74 911s. I pulled the heater lever to defrost my windows last nite. This morning I returned the lever to it's original position...but I still continued to get heat flow...What should I look at??? Whats broke or needs adjustment???

Thanks

Jack -- does the 72 have a heater blower? I thought those weren't added until later. Anyway, sounds like a heater box valve to me, if it's getting hot but won't turn off.

You're right. The 72 didn't have a separate heater blower. I believe the main engine fan provided the air pressure for the heating system.

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Jack Olsen
1973 911 T sunroof coupe