Some defi or standard gauge install *facts*
 

1. The left-most female spade port on the fuse-box is NOT constant 12v as some posts have indicated. The right-most is 12v accesory on, as tested by voltmeter. This goes along with what others have said.

2. If you're looking for constant 12v, there is a row of 2 large blue molex connectors underneath the steering column that you can see without even removing the lower column cover. Tap into the BOTTOM-LEFT corner wire/lead of the left-most blue harness for constant 12v.

3. Indeed wiring only the control-unit illumination wire to the ashtray will result in inverted voltages from the dimmer. If you wire the ground to the other wire, two outcomes are possible depending on which wire you use for ground and which one you use for illum.:

a. The gauges completely turn off upon full dimmer.

(flip wires now)

b. The gauges work fine at full-dim, but with decreasing dim, the PWM signal which is modulating the ground causes the control-unit to shutdown, resetting the gauges when you bring dimmer back up to full and also temporarily screwing up your memorized peak reading. The way the dimmer works is the PWM signal is just oscillating the ground, effectively turning on and off the lights. However, this happens fast enough to not be noticable as an on/off effect to the visible eye. Of course any electronic device will not like it's ground being flipped back and forth like that, which is why the control unit effectively turns off if you go low enough.

4. If you can find the wires, you can use the cigarette lighter illuminated bezel leads instead of the ashtray under the center column.

:sniff: :sniff: You smell that? I smell an archive thread.

Good info :)