'78 ventilation controls

[Superman]

I'm partly just documenting stuff for people to refer to in Searches, and partly asking questions. Heater controls on '78s a '83s are different. As you can see from the pictures, the '78 controls have an additional lever for fan speed. According to my understanding, they also have a light in the upper right corner which turns on and off according to fan operation. It is my understanding the '83 controls lack this last feature. I like that feature, so I am removing the '83 controls in favor of the '78 controls. The car is a 1978.



1983 Controls






1978 Controls

[Superman]

Here is a picture of the '78 unit. Significantly, the wiring is exactly the same as the '83. Both have a round plug with three prongs (on the left). Both have a ground wire (long wire to the right). Both have one wire, for one light, on the right side of the control panel (short wire to the right).

How, if both control units seem to have the same wiring, for only one light on the right side, does the '78 unit work differently. I will be figuring this out. Hoping someone has information for me.

Here is a really specific question: The ground wire for the ('83) unit I am trying to remove snakes up behind the glove compartment, requiring significant disassembly to remove. Shouldn't this ground wire terminate closer to the ashtray?

[kach22i]

Interesting, the 1977 unit is all mechanical with metal push/pull rods slipped into lever arms.

[dipso]

My 75 looks like your 83 picture. Three controls, not four.

[Time Collector]

I have a 1978 and my controls have three levers like the one you are calling the 1983 one on top. My friends 1982 has four levers and they are both California original cars.

[Superman]

Originally Posted by Time Collector

I have a 1978 and my controls have three levers like the one you are calling the 1983 one on top. My friends 1982 has four levers and they are both California original cars.

Your cigarette lighter 'icon' is different from my '78, but the yellow and green fog light and defogger knob icons are otherwise the same. Interesting.

Thanks, guys. This is helpful for posterity.

[Time Collector]

I am the second owner and this car was purchased at my local dealer in 1978 by the first owner.
It was also serviced by them thru out its life. I replace the radio 2018 for blue tooth capability.
The original sticker states that its equipment for California, if that makes a difference.

[mike sampsel]

Originally Posted by Superman

How, if both control units seem to have the same wiring, for only one light on the right side, does the '78 unit work differently. I will be figuring this out. Hoping someone has information for me.

Here is a really specific question: The ground wire for the ('83) unit I am trying to remove snakes up behind the glove compartment, requiring significant disassembly to remove. Shouldn't this ground wire terminate closer to the ashtray?

The fan light gets grounded by the metal leaver on the ‘78.
Not sure if ‘83 kept same mechanics and just omitted the light, which can turn on even if fan does not run

[mike sampsel]

Here is a pic which shows the ground contact for the light. Borrowed from another post

[Otter74]

This is not a difference between model years, but a difference between AC and non-AC cars. Cars originally equipped with AC have the control panel with a single lever on the upper level. On Cars originally not equipped with AC, there are separate levers for the fresh air control and fan.

[7783911]

my 77 has 4 sliders

[Solamar]

1978 w/out factory AC

Four control knobs, three illumination lights with dash lights (two on left, one on lower right) and top right illuminates when fan is on.

Took me a bit to understand the symbols on the blue bar. The left symbol is the center dash vent (all fresh air directed there). The right symbol (up and down arrows) allows the air to be directed to either the top vents or the foot vents dependent on the position of the lower black knob.

To shut off all fresh air you move the top left lever all the way left, directing all air to the center vents, then shut the center vents.

Clear as mud?

[Superman]

I have discovered that both styles of controls provide this feature. My '78 controls, with two knobs at the top, and also my '83 controls, with only one knob at the top, both have the light in the upper right corner which illuminates when the fan is turned on.

However, on both of my controls the fan light glows considerably more dimly than the others. I wish I knew why.

['78 SC]

Originally Posted by Superman

However, on both of my controls the fan light glows considerably more dimly than the others. I wish I knew why.

This is from my 1978 911SC. Photo is with instrument lights and fan on. Photo is pretty accurate, if anything, the "DEF. OFF" and "DEF. MAX" lettering appears slightly dimmer, yellower and unevenly lit in person.



The car has factory air conditioning. I am the original owner and these controls have not been worked on. Original bulbs.

[Superman]

Very interesting, Steve. On both of my controls, same as yours ('78 and '83), that light is dimmer. Even when I switch the glass lamps around. Hmmm......

[Superman]

After further consideration, I notice your '78 controls are the same as my '83 controls, and different from my '78 controls (with two knobs at the top).

[frankc]

Originally Posted by otter74

this is not a difference between model years, but a difference between ac and non-ac cars. Cars originally equipped with ac have the control panel with a single lever on the upper level. On cars originally not equipped with ac, there are separate levers for the fresh air control and fan.

+1. Having retro-fitted the non-A/C controls and ventilation in my car, I can confirm this is true.

[7783911]

I have same issue as superman (minus Kryptonite) in that my illumination ios very week..I will experiment with new bulbs, leds etc as well as check the grounds to see if that help and will repost finding. My fog light and defroster are essentially useless even with new bulbs (leds),,,

Biob

['78 SC]

Just for reference, here's the panel for my 1983 911SC. Fan graphic is bright. Car originally had AC, but that has been removed along with the entire ventilation system (it's a track car). Bulbs for lower indicators probably burned out or gone. The fan graphic in upper right is different than for 1978.



Steve

[RWebb]

Did you unhook the cables at the blower to remove the heater control assembly?