Docking light not working

[badrano]

I have a 2005 Chap 204 SSi. When I bought the boat, the one docking light was in-op and I figured it was just a blown bulb and searching the forum, I found that it is a MR-16 style bulb.

I replaced the bulb, but it still doesn't work. Long story short, I took a voltage reading on the bulb socket and it was around 9V. Thinking something might be up with the socket, I pulled the whole light fixture out and measured the voltage on the harness connector and it was still 9V. So, just to make sure, I measured the battery directly and it was at 12V.

It's obvious that there is a significant voltage drop, but I would have thought the bulb would have at least lit up but be dim. The replacement bulbs I got are halogen. Do halogens require more that 9V to light up?

 

[Scott Danforth]

most likely you have a really bad connection either at the switch or the ground buss terminal

 

[badrano]

I didn't even thing of a bad ground. Thanks.

My next step was to take a reading at the switch and on the working light. I'm not sure yet if the switch is a DPST where each light has its own set of wires off of the switch versus a splice somewhere in the harness.

 

[Silvertip]

I'm betting the hot lead off the switch is split at some point to feed the light at each side. I would also NOT be surprised if you found each light grounded to the aluminum hull. If not, then those wires also would be split with the ground made at the ground bus or directly to the battery. If one light works normally, then the switch is not likely the problem.

 

[badrano]

I just pulled the dash panel back to take a look at the switch. It's a SPST switch. It only has the one blue/green stripe wire. I would have to agree that there is a splice some where along the harness. The painful part is trying to figure out where the splice is since the harness goes behind the stbd side front seating area.
There is a ground bar under the dash, so I don't know yet if the grounds for both dock lights are spliced together as well.

Sounds like I'll be pulling apart the bundle of wires under the dash to identify the harness the goes forward to the dock lights and nav light and then go from there.

 

[Mohawkmtrs]

Why not run a redundant hot wire to the inoperative light to confirm/rule out a bad hot wire before tearing everything apart?

Ditto for the ground circuit.