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Installed everything today and all the lights work only the shifter indicator light doens't work.
Where does that get ground from?
Check the AIM where Alan 71 suggested.
After that, the best I can assist with is:
1969 Shop Manual diagram [original; differences from robertea’s color diagram, same principles] “Console cluster” ground circled for location clarity in a B&W diagram. Does your shift indicator look like this? (underside shown) ORG circle, bulb location ; GRN arrow, potential ground tab locations [Quick google search; apologies for resolution]
FWIW Primoz, 85-90% of the cluster bulbs are:
GRAY, single wire, power [B+, 12V]
So they need a ground source to complete the circuit…
Best way to ground [common small] loads (i.e. bulbs) is a metal frame with a single wire to a known good ground [common, chassis].
That’s why the:
Speedo
Tach
Center gauges
…have single GRAY in [bulb power], and shell/casing/housing/frame GROUND out.
Think of those metal panels as the ground. That’s why there’s usually a bolted-in / screwed-in male terminal for a female Packard 56 terminal in a 1-wire connector.
Does that make sense?
John
[EDITS: phrasing, pic re-upload]
Last edited by The_JC_L46; Mar 7, 2026 at 06:03 PM.
So.
The new cigarette lighter housing has an additional ground which original didn't have.
I used that to connect another ground wire to the center console bracket and now everything works like it should.
Of course I had to make a ground wire because original ground wire connects to heater control. Now to the net question.
My brake light on the das doesn't light up when I pull the handbrake.
How to check if the switch is faulty?
It looks like a very simple switch but still.
I really don't want to take a dash apart to check if the bulb is still intact because all the other bulbs are working fine and because the dash is all together.
Buuuut… now I have to revise what I said before about grounds. …a lil bit.
That switch when pressed (closes the circuit) is the ground. As in: switch makes the ground connection for the bulb.
The wire is 20 Tan (20T) in this diagram:
Since you’ve been checking all your bulbs, AND if you’re ok with turning the key to ON…
Key / Ignition ON
Press Brake Lever button
’Brake’ warning light in Tach housing should turn ON
[The 20P (pink) wire is IGN Switched power, so the key needs to be on to test it.]
A few of my switches were ‘gummy’ and I had to repeatedly push-on-off-on-off-repeat to get the (glove box light, etc…) to start to work.
In the diagram above (even though it’s a snip), the 20T goes to the firewall / bulkhead and back to the other 20T in the same diagram [they’re right next to each other]. From the firewall, it goes to the brake fluid warning switch in the brake system [low fluid / fluid loss indicator that also turns the ‘Brake’ warning light on].
Are you following?
Makes sense?
Last edited by The_JC_L46; Mar 8, 2026 at 02:05 PM.
