Carl Muckenhirn

Now that the weather has warmed, I'm noticing that my feet are getting hot.

The HVAC controls are set to panel and the temp is on "blue." After an hour or so, the footwells become hot. The heat seems to be emanating from the heater tubes on either side of the foot well.

Is there something amiss? Are there any servos in the engine compartment like in the older 911's that open or close to keep the heat in back? What controls them? Do I just need to learn to live with this?

It's kind of strange to be running at 80 and heat is wafting from the back of the car!

TIA,

carl.

shaker71

Have you checked the tubes to make sure they aren't crumbling? My feet were so hot that I could hardly stand it. I discovered a minute crack in the passenger side tube. When I grabbed it the whole tube crumbled. I replaced both tubes and everything is COOL now.

Carl Muckenhirn

Yes they are very old and brittle, but no holes yet. I'll replace and see how that goes.

thanks,

carl.

Riccardo

Carl,

Could be the stuck servo sindrome. I don't know how to fix it, but I do know that its not uncommon for them to get stuck in one position. The symptom is that you end up getting boiling (or freezing) air coming from one of the vents. There must be a vent near your foot, so this would explain it...

Carl Muckenhirn

When I feel the warmth, it is not blowing. I can put my hand in each of the vents below the dash (the mail slot) and the two plasic covered "dishes") and don't feel any heat (they are actually cooler than the ambient air down there).

Are there servos in the engine compartment that will limit flow of air into the heater hoses in the kick panels?

carl.

Roly Baldwin

Carl,

The servos at the back of the luggage compartment only control airflow within the large plastic heating system unit that lives under the servos and not to the hoses in the kick panels. I think the heat mixing chamber itself is served by those hoses, rather than the other way round.

If it helps, I have a complete spare unit out of the car - I can take some pictures if you like.

Herbie

I think this isn't a servo problem.

Hot air blows from the hoses between chassis and mixing chamber.

Hot air is pressurized in that hoses also when temperature **** is at "blue" position.

On the left side, the hose is near left feet, to see it have to remove side footwel panel.

Turn engine on and check with your hand any air blowing.

Repeat the test on the passenger side; the hose is near the check connector.

Herbie

Carl Muckenhirn

Herbie,

Your on to my problem. On older 911s one of the levers between the seats controlled a "valve" where the heater hose left the engine compartment going to the rocker panels.

I can't tell if those "valves" are still there (but electronically controlled).

If they're not there the I guess the heat is a leak in the heater hoses in the kick panels. (the one on the right is old, but doesn't appear to have any holes - I had it out while installing a new radio. Haven't looked at the one in the drivers foot well.

Thanks again everyone for you help.

carl.

shaker71

It doesn't take mush of a leak to get it cook'in down there. I'll bet there's a leak.

Randall G.

Hey Carl,

As you suspect, there aren't any electronically controlled valves for the heat back in the engine compartment. When there's no demand for heat, spring-loaded valves dump the excess heat into the rear wheel-wells.

Randall G.

Roly ... would love to see some pictures of the removed unit, as it might help reveal some of the mystery beneath.

Roly Baldwin

You want pictures? I got pictures...

<img src="http://www.nethereal.co.uk/964/heater_servos/addendum/stitched01a.jpg" alt=" - " />

<img src="http://www.nethereal.co.uk/964/heater_servos/addendum/stitched02a.jpg" alt=" - " />

<img src="http://www.nethereal.co.uk/964/heater_servos/addendum/stitched03a.jpg" alt=" - " />

<img src="http://www.nethereal.co.uk/964/heater_servos/addendum/stitched04a.jpg" alt=" - " />

Randall G.

Great pics, Roly! Looking at the shop manual, and studying your pictures:

-The top photo is the bottom, when installed in the car.

-The second photo from the top is the passenger compartment side, when installed in the car, but would be flipped, putting the thick part on top.

-The third photo would be the top, when installed in the car.

-The bottom photo would be the luggage compartment side, when installed in the car.

Sound right?

I have some ideas, but any thoughts on which duct supplies what? For example, in the third pic (top view), the duct looking straight at ya' is for the fresh air intake.