Bunk light switches

The Volvo has a bunk light (dome light) that lights up the sleeper. A while back I converted it to LED. It has a couple switches that turn it on. One is on the bank of switches next to the driver's door. The other switch is with the sleeper controls. It struck me as unhandy that if the passenger wanted to turn the light on they had to crawl through the dark to find the switch. I decided to add a more centrally-located switch in the overhead switch panel next to the CB.

A small additional challenge is the way the light functions. Most lights use an on/off switch. Not Volvo. They use a momentary SPDT switch that sends 'on' and 'off' ground pulses to a lighting computer, which in turn controls the light. This means any additional light switch I add must tie into those two lines. The driver's switch is physically closer but I learned from the voltage guage project that running wires up the A-pillar is a major pain.

I have already ran antenna coax down both sides of the truck interior from an earlier project, so running more wires would be familiar ground. I also noticed there is a switch panel for the upper bunk. Hmmmmmm...I could add a light switch there, too, for someone in the upper bunk. I decided to tap the wires from the switch in the sleeper controls.


The two wires I need to tap into are circuits 509A and 509B. I found these at the end of the blue connector on the rear of the sleeper controls (in my VNL780).


I ran the wires behind the trim to the upper bunk switch panel to a terminal strip. Here I used two-sided tape but I wound up screwing it to the wall. I used a piece of trailering wire I had laying around. In this picture:

- Green is the 509A circuit that turns the light on.
- Yellow is the 509B circuit that turns the light off.
- Brown is ground.
- White is the 141 or "dashlight" circuit that illuminates the switch function. I couldn't find that circuit in the sleeper control panel so I will tap into that circuit in the overhead switch panel. I ran that wire up there for voltage gauge illumination.


The upper bunk switch. It works as intended. Volvo also uses momentary SPDT switches for the IDLE/DIAG and FAN SPEED switches. They are much easier to find than the official bunk light switch.

Update: I have since found the correct switch on Ebay.


The switch panel on the overhead shelf. The bunk light switch here is a more convenient location for the passenger...or the driver, for that matter. The Carling switch on the lower left switches 12V for the CB, radar detector, and a future camera.


The 'red light' switch controls a red LED light over the passenger seat. It's less distracting for the driver.



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