With the upper and lower dashboard in place, the instrument panel could be reinstalled. Now as part of the rewiring I had decided to eliminate the dash panel light switch. I really didn't see the point of this. Why would you want to drive at night with all the instrument panel lights off? The Series III had this feature as well. And it's just one more switch to worry about.
I'd already removed the dash panel light switch in order to install one for the interior light, so I needed to wire the instrument lighting so that it came on with the vehicle lights. The new switch panel can be seen in the next photo:
The instrument panel connections themselves were fairly straightforward; they only go on one way. Although the focus was a bit off in the next photo you can see these panel connectors - they're the long white things.
Now I'd done some research and read that the way to eliminate the separate switch for the dashboard lighting was to connect the two red wires with the two red/white wires. In the photo above you'll see that at the top of the photo the red/white and red wires are connected together. This photo was taken before I did any testing.
However, when I reconnected the battery and switched on the main lights using the stalk on the steering column, I immediately noticed that these wires started smoking, so I switched everything off again pretty darn quick! After scratching my head for a bit, I separated these joined wires, and using a crocodile clip test wire, inserted a temporary 5A fuse between the wires.
Switching on again, I found that this time no instrument lights were lit. At all.
To cut a long story short, I discovered that because I had replaced all the instrument bulbs with blue LED bulbs, these were not drawing enough current to power the circuit. If an ordinary 12V bulb was connected between the red and the red/white wires, everything worked absolutely fine. But I didn't particularly want a hidden bulb behind the dashboard - I needed something else to provide some added resistance to the circuit.
So, as a test, I took an old panel switch left over from the dashboard of my 109, and connected that between the red and red/white wires.
Er, yes, but.
I haven't actually eliminated the dashboard lighting switch, have I? I ended up fixing it to the right-hand side of the dashboard on the air vent control panel. It will be in an always-on position, but seems to provide enough current draw so that the dashboard LED bulbs are illuminated when the main light switch stalk is operated. Very weird. So in effect I didn't eliminate the dashboard light switch, just moved it.
I suspect if I had not used LED bulbs, everything would have been fine.