ElectroClassic EV
Classic Cars Reborn into the Electric Future

Take the Heat

The Holy Maximum Defrost

Mounting the blower and flapper boxes seemed the next logical step after the wipers were installed. The 914World forums was very helpful and warned that everything here is a tight fit, but luckily I didn’t find it too excruciating.  On the other hand, the cable linkages can be confusing, and I feel compelled to share some further clarification.  My quest to fill the information gap may seem pedestrian to most folks, but a few might find nirvana here.

I’m just going spill the raw data now, and then explain later in English.  Here comes the nirvana part:

1 – Top dash panel slider connects medium length control cable to linkage on fan blower flaps.  Slider pushed fully left puts fan off and flaps closed, and fully right puts fan on and flaps open.

2 – Middle dash panel slider connects short control cable to top linkage on rear of driver side flapper box (facing rear of car).  Slider pushed fully left diverts fresh blower air to floor vent, and fully right diverts fresh air to defroster nozzle and dash vent.

3 – Bottom red dash panel slider connects long control cable to bottom link on front of driver side flapper box (differs from forum tutorial).  Slider pushed fully left diverts hot air (originally from engine) to floor vent.  Fully right diverts hot air to defroster nozzle and dash vent.  This slider only controls hot air routing, while heat volume was originally controlled by the red lever on the tunnel.

4 – Two remaining linkage cables ensure the passenger flapper box copies the actions of the driver flapper box.  First cable runs from driver box rear bottom link to passenger box front link, and second runs from driver box front top link to passenger box rear link.


Now back to English.  The above image shows the three cables coming through the bulkhead that are controlled by the slider levers on the ventilation dash panel. Notice that the cables are different lengths.  Also key is the text on the dash panel stating that maximum defrost requires the two top sliders be positioned completely to the left, and the bottom red slider all the way to the right.  It also helps to stick some fingers into the box vents to feel the flappers in action.

What follows is a deeper explanation of flapper box nirvana, but I’ll try to keep it brief.

For starters, the top slider on the dash panel is labeled with fan air volume graphics, and obviously should be connected to the fan blower.  For maximum defrost mode, this slider is fully left, which closes the fresh air flaps and turns the fan off.

The other two control cables connect to the driver side flapper box.

The bottom dash slider’s red color denotes heat, corresponding to the driver flapper front linkage which diverts hot air either to the floor or the defroster nozzle. When this slider is pushed to the right in maximum defrost mode, the cable must be connected to the driver front bottom link to send full heat to the defroster nozzle, and not the floor. (The 914World tutorial differs here.)

Finally, the middle slider operates the short cable, which can only reach the driver flapper box rear linkage.  This flapper normally channels fresh blower air either to the defroster/dash or the floor.  However, in maximum defrost mode, the fresh air defrost flap must close to prevent hot air from escaping from the other side of the flapper box.  This narrows the short cable connection to the driver top rear linkage.

The passenger flapper box just copies the actions of the driver flapper using those two linking cables as described above in nirvana #4 above, so it pays to get the driver side working correctly first.

All of this was tedious to write, and I think my conclusions are correct, but I invite any differing opinions.


Here’s a shot of just the fresh air blower in position, without the flapper boxes.  I found that attaching the control cable and electrical connector prior to installation was cumbersome, and attaching them afterward was not so difficult.  The same goes for the front flapper connections, which are directly accessible and easy to work on.  However, the rear flapper box cable connections are a bitch to work on once the flappers are in place.  I seriously recommend making all of the rear flapper box cable connections before installing them.


This is a look under the dash at the floor vent installed under the driver side flapper box. I agree with the tutorial that the flappers go in easier with the defroster nozzles already attached.  The nozzle end just needs to be pushed as far as possible into their dash deck slots before the bottom of the flapper box will fall into place.


The image above shows the passenger flapper installed incorrectly (upside-down).  One hint is the lack of clearance where the blower hose meets the passenger flapper.  Furthermore, the control cable connections were mondo-confusing until discovering the flapper was inverted by comparing it to the 914World tutorial and my disassembly shots.


Here is the finished install, with the passenger flapper righted and with all the correct cable connections.  The original 914 design used an auxiliary fan to push hot manifold air from the engine all the way up to both flapper boxes.  Since there will be no engine, my plan is to install a small ceramic core electric heater on the bulkhead below the original blower, and force hot air into the flappers from there.  It never rains in California, but sometimes it gets pretty cold.  More on that later.


One Response to “Take the Heat”

  1. Beep Beep M Beep Beep Yeah!

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