reid wrote:
If we leave [pin B] at 14 v. all the time, then it is too bright at
night.

If it's got a software setting (something you can adjust by pushing
buttons on the front panel) for LCD contrast, have you twiddled it?
Sometimes LCDs behave oddly when that control is all the way at one
end of its range.

I cannot figure out if we've missed something or not. Their
instruction about connecting to the lighting circuit implies that the
pin has no power during daylight operation.

I have no specific knowledge of this radio, so at first I thought it
might be doing something fancy. But Googling finds a post at
http://www.opensubscriber.com/messag...m/3335471.html
says that the lighting circuit inside the radio is pretty simple.
Basically, there are some lamps inside the radio that have one side
grounded and the other side wired to pin B - you have to provide
some power to pin B to get the backlight to work at all.

Another post in that thread
http://www.opensubscriber.com/messag...m/3327934.html
has a link to a wiring diagram at
http://www.aeroelectric.com/Installa...ion_Wiring.pdf
which might be useful.

It doesn't take much voltage drop to substantially reduce the light
output from an incandescent lamp. If you don't have a dimmer control to
connect the radio to, you may need to install one for the radio, or even
a "bright/dim" toggle switch that switches a resistor (voltage drop
whatever you want) or diode (voltage drop 0.5-1.0 V) in and out of the
radio lighting circuit.

Disclaimer: This is based on experience with ground vehicles and
equipment. I don't have an A&P; I don't even have a TG&Y. Your
mileage may vary.

Matt Roberds