Medallion/Underwater light compatibility

[Brianrzr]

I’ve got an interesting dilemma with a underwater light install on my ‘14 with the Medallion system. First, I located the harness blue and black pair at the transom, that powers off and on with touchscreen as it should. Interesting fact, multi-meter shows 11.79 volts at harness while both batteries indicate 12.6. I created my own pigtail that splits from a single input into two outputs with 2-pin Deutsch connectors. Red probe to blue, black probe to black +11.79 volts, swap probes and get -11.79 v as expected. Blue is positive as it should be. I connected a extra courtesy LED which requires correct polarity and both leads lit on and off with the touch screen. I installed two Shadow-Caster SCR-16-GW bronze lights, and wired red to blue, black to black. THEY DON’T LIGHT! I re-installed test light, and it operates correctly. I can jump the Shadow-Caster lights to the battery and they light correctly, they just do not operate off the Medallion touch screen, even a single one. Is the Medallion capable of powering a Shadow-Caster? I have not tried switching polarity without talking with them for fear of frying them. Anybody have any idea? I can wire and add a switch if I have to, but I should not have to. And why only 11.79 volts at the connector?

[freeheel4life]

This does seem odd. I forget...is the underwater light in the big long box behind the kick panel?? I'd back up to there if so and see if the 4ga wire into that box is same as battery voltage. I'd also check the voltage across the fuse for that circuit(have seen voltage drop thru corroded fuses before). You can also check the voltage on the output post that the female spade slide on to at the box.

If youve already verified polarity and bench tested them this is definitely an odd one. I don't recall underwater lights being driven off a PDM until Murphy PDMs started getting used....BUT all that being said I have had to turn underwater lights on and off via relay and just using the black and blue for the relay coil. Though that was running 4 lights on a Murphy system.

[chpthril]

So you've got 12.6 at the battery, whats the Medallion Viper got? 11.7 is quite a drop, so you need to see if that drop is to the helm or just the LED output.

Even once the voltage drop is resolved, id likely use the LED output to a relay and power the lights through the relay from a more substantial 12V+ supply, like the main supply to the viper.

[Brianrzr]

As most would probably understand, I was more than a little irritated. I just did the simple trouble shooting I described and covered it up, I’ll get back into it in couple days when it warms up. Great suggestions about haw to trouble shoot at the Viper box, but I’m not familiar with the PDM term, what is that? My other thoughts were that it may not handle the initial amp draw from the combined lights, because my test light is just a small single LED, but I even tried with a 6 LED Shadow-Caster unit with the same results. I like the idea about powering a relay. I’ll call both tech departments at Medallion and Shadow-caster tomorrow.

[bsreid]

Having a 1v drop from the battery and medallion seems like a lot. But my initial thought would be to just run the lights directly off the battery and a relay linked to the medallion to control them.

[chpthril]

PDM is Power Distribution Module. its the brain the take the touch screen commands and makes them into voltage outputs.

[freeheel4life]

Without going down the rabbit hole PDM is as stated by Mike(because he knows he's the man)

Your year has a somewhat crude system. Pull off the kick panel and there is long black rectangular box. It's taking digital inputs from the screen and turning into analog outputs thru the box(a PDM).

i cant remember if underwater lights are in that box. It's well labeled once you pull the cover off. If underwater lights are controlled via this box it's a good place to see if you have upstream or downstream problems with the voltage drop issue.