First of all let me say how unbelievably fantastic this site is. I would be lost without everybody's knowledge, experience and willingness to help.

I'm 99% done with refurbishing my wiring harness. The one remaining question is how the illumination for the heater controls is supposed to work.

There are four light sockets on the back of my heater controls.
Click to view attachment

According to the wiring diagram, it looks like one of the lights is supposed to come on when the fan is turned on and the other three with the dash illumination.
Click to view attachment

Do I have this correct?

The wiring harness is a 1973 and I have no idea what year the heater controls are.

Thanks.

George

You have it correct. The ‘FAN’ light illuminates when you move that slider to the right. If I remember correctly it only comes on when the slider gets to the I, II or III position.

As a side note, there are notches in those locations inside the slider housing. So you should feel a slight click into the I, II and III positions when the slider reaches that point. There is a small ball bearing held u set a spring loaded clip that engages that notch in each position. Sadly, most of the controls I have seen that ball is missing. Mine included. I tried a BB (.177 I believe) from a BB gun but it was too large. If yours is missing maybe you’ll find something around the house that can replace it.

Good luck!

Update: on your slider the Blue tile is what should light up. Later models say ‘FAN’.

Thank you Rob.

Now that you've confirmed my suspicions, I can make a little wiring harness for the other three lights.

BTW: It looks like my heater controls have a cupped contact (convex side down) that presses into the electrical plates for the fan controls.

Click to view attachment

Perhaps by 1974 they did away with the ball bearing.

George