Heater vent flaps

[280sl1968]

I am in the process of replacing the filter pad under the air intake cowl.

While doing this, I noticed that the left side hot air flap (the one also connected to the valve) doesn't quite fully close, and even with the lower left lever all the way to the left, it is still open by about a centimetre or so. Assuming this shouldn't be the case, how is it adjusted?  Can see the threaded rod connected to the flap and the valve with a ball joint type connector at each end. Do these just pull off and push back on so that the length of the rod can be adjusted using the threaded end?

Also, the air cowl filters have a spring loaded wire frame on one side that clips into the air intake walls. I think it makes sense for the frame to sit on the underside to support the filter, but I see some photos on this forum with the frame on top. Probably makes no difference to the functionality, but would be good to know which way this should really go.


Thank

David

[66andBlue]

Technical Manual to the rescue! 
http://www.sl113.org/wiki/uploads/Electrical/Heater_valve_operation.jpg
Take a look at this picture and you'll see how the flap and the heater valve work together.
You need to find out what it is that prevents the flap from closing (a) the wire that connects the flap to the control lever or (b) the linkage between the valve and the flap. But adjusting one will change the other!
The wire frame on the cabin air filter should face down. You want wires somewhat protected from the elements and also prevent the filter material from sagging:
http://www.sl113.org/forums/uploaded/66andBlue/20088314305_FreshairFilter.jpg

[280sl1968]

Alfred

Thanks for the confirmation on the orientation of the filter.

The photographs on the heater flap are also a great help. I think I am getting confused between what is 'open' and 'closed'.

When my lower left lever is fully to the left, the flap should be open, correct? i.e. sitting horizontal. When it is fully to the right, the flap is 'closed' and up at about 45 degrees to the vertical.

On my car, when the lever is fully to the left, it is not coming down so that it is fully horizontal (the right side flap does)'. it is always still up about a centimetre, so I assume this means that there might be some cold air mixing in with the hot?

The valve seems to be moving as shown in the links you posted.

I'll post a picture shortly.



David

[66andBlue]

David,
you need to look at the other photos in the manual (http://www.sl113.org/wiki/Electrical/HeaterControlValve) that show the air flow through the heat exchanger when the the left warm air lever is open (all the way to the left), the flap is open, and the valve is open. Under these conditions the air flow is directed forward (driving direction) and forced downward through the exchanger. Some air of course will also flow directly downward along the backside (front is engine side - back is cabin side) of the exchanger because the flap does not close the opening downward!
When the flap is closed in the vertical position (valve is closed, lever to the right) then the air just flows down into the distributor box.

[Tomnistuff]

Alfred,

When I first saw the photos and labels on the “heater valve operation” photos (linked above in reply #1), I was confused and decided to study how it worked on my own car.  What was confusing for me was the flap labeled “Flap closed” when it is vertical and the heater flow valve is labeled “Valve closed”.  I agree with the “Valve closed” label, but “Flap closed” to me implies that there is no air flow past the flap which I do not believe is true.

It appears to me that the left flap is actually a heater core air bypass flap which closes the heater core air bypass hole (flap horizontal) and opens the heater core coolant flow valve when the lower left slide is moved to the “more heat” direction, thus forcing air only through the now hot heater core and down into the blower fans.

When the slide is moved to the right (less heat), it simultaneously opens the air bypass flap (flap vertical) and closes the heater core coolant flow valve, allowing incoming air to bypass the heater core while not closing off the air flow through the heater core, because it is cooling off anyway.

So, in my opinion the label “Flap closed” in the left photo should read “Heater core air bypass open” and “Flap open” in the right photo should read “Heater core air bypass closed”.

The passenger side heat control, of course, will only regulate the quantity of heated air to the passenger if the driver’s heat control is partly in the direction of “more heat”, so the heater core coolant valve is at least partially open.

I think my understanding is also in agreement with the other photos and explanations in the Technical Manual.

I’m taking a big risk in writing this, because it’s possible that I have completely misunderstood how the system works.  It that is true, perhaps it’s even more important that I post it.  If I am wrong, please help me understand where I have gone wrong, because I am currently trying to put mine back together and I don’t want to do it wrong.

This site is the most wonderful car restoration aide I have ever seen.  Thanks everyone.

And, don’t hesitate to pile-on if I am wrong.

Tom Kizer

[66andBlue]

Hi Tom,
I agree with you that these controls are the most confusing on our cars and the previous discussions by Al Lieffring and Bob Possel on how the valve should be installed and how it opens and closes is a prime example.
However, I believe our current problem is only imaginary and not real, like trying to decide whether the glass is half full or half empty.
When I put the photos on the left side together (no heat, cool air only) I labelled the flap as "closed" meaning the air flow through the heater core is closed.
You prefer a label "Heater core air bypass open” which is of course means the same - the cool air does not go through the core but straight down to the distributor box/fan as indicated in the photo showing the air flow (green line and arrow = cool air/ red line and arrow = warm air).  
What you wrote about the passenger side heat control is correct and I have wondered about this ever since I put my 230SL together again.  If the driver decides to shut off the heat there is nothing the passenger can do to receive warm air.  

[280sl1968]

So, here is a photograph of the left side flap on my car. This is taken with the lower left lever fully to the left and so the valve is open and the flap is 'open'. As you can see, it isn't quite coming down fully to the horizontal position (compared to the left side), so I'm assuming this means that some cold air will still be entering the cabin.

How is this best corrected? Is it a case of adjusting the length of the rod connecting the flap and the valve at the threaded ends?


David

[66andBlue]

Others may do it differently but I have always adjusted the control wire to the flap first and then the linkage to the valve.
You wrote that your control lever is pushed all the way to the left, that is the lever hits the end of the slot. This means that the wire is too short and not pushing the flap completely forward. Disconnect the valve linkage rods, loosen the castle nut on the warm air control lever, move the lever to the right a bit, tighten it again and now push all the way to the left until the flap is in a horizontal position and wont go further. If the lever is not all the way into he left corner, loosen the nut again, push the lever left and re-tighten. Now check that the flap closes the entry to the core completely when you mover the lever all the way to the right! You may have to find a compromise between both positions and the control lever moving all the way to both ends.
For me it was more important that the flap closes the heater core off than a bit of cool air coming in when the heat is on.
After the flap is adjusted you now need to adjust the linkage rods so that the valve opens and closes completely.
Here is another picture of the flaps open and closed.

[Tomnistuff]

Hi Alfred,
I think, in principle, we are in agreement.  Perhaps the only place where I may be trying to pick the fly s___ out of the pepper is your term "air flow through the heater core is closed.  It looks to me like the air flow through the heater core is never closed except when the outside cowl vent door is closed.  When you say "closed", to me it means that the bypass is open and air flow through the heater core is reduced only by its fin restriction and the fact that it is easier for the air to bypass through the flap opening.  Anyway, it doesn't matter because, under those conditions, the heater core coolant flow valve is closed and the heater core is cooling off or is already cold.
Peace!
It is, however, unfortunate that, instead of using throttle type ball and socket linkage, they (DB) did not extend the wires of the two "heat" levers beyond the two flaps to both operate the heater core coolant valve so that either the passenger or driver could open the heater core valve when they want heat.  The two wires operating the same coolant flow valve could be configured so that each "overruns the other against a spring loaded normally-closed coolant control valve.  It's hard to explain with words only, but it could be easily done.
Anyway, it works as is so I will stop speculating.
Tom Kizer