I replaced the bulb on the back of the heater-ventilation controller on the right today. The bulb lights up when the fan is engaged.

Question is on the left there seems to be a bulb socket, but no bulb or evidence of there ever being one on the left. Did the early 914's have a bulb on the left?

You has the early one like the European version

The German version doesn't have a bulb behind the red
sign also no bulbs behind the arrows

Also, just in case you don't know it yet, the forum below is specifically for this kind originality question.

http://www.914world.com/bbs2/index.php?showforum=44

Try and bulb in there and see if it works?

Only the right side lamp works on mine as well 1970 U.S model

Yeah, one would think that there would be a bulb there to show when the heater fan in on. So I put one in. I took the power from the blue side and used the heater lever as the ground; the light only goes on when the fan is on (the lever is the ground for the fan). I've posted this before, but here is the pic again. Also, I believe that the arrows glow in the dark.
Click to view attachment

There is nothing to trigger Heat On in a -6 wiring.

Does the 6 have a fan and use the same/similar lever as the 4? The 4 did not have the wiring; I had to run my own.

This forum is great, instant answers to even the smallest detail !

Thanks guys !

That light mod is on my list of things to do during the rebuild.