240 Sundeck gauge problem

C

Chris C

New Member
Sep 4, 2018
7
Stillwatwr
Boat Info
240 Deckboat 2007
Engines
350 Mag Mercruiser w Bravo III drives
Just bought a 2007 240 Sundeck. Took it out for a long weekend. On 2nd day gauges went out, except for Tach. Tried to reset pushing Mode & - and also shutting off battery, neither worked. Then next day when turned off battery, backlights on gauges stayed on. Anyone have an idea?
 
Yup. Happened to me. Same exact boat. (Nice one by the way)

In the storage area forward of the helm is a round harness connector with a bunch of wires.

Disconnect it, apply dielectric grease and reconnect.

No issues for me since I did that last year.
 
Awesome! Thanks so much for that. I really appreciate it. I will try next time I am at the Marina! Thanks again!
 
Hi. I’ve got ‘05 version of same. How could backlights stay on if battery is off? As I understand it, the only things with power when battery is off is auto circuit for bilge pump and radio memory.
 
Strange I know. Since last post, I have been to marina. I unhooked the wire harness as said above. With wire harness disconnect, the guages were still lit up even then. Battery switch was in off position. Key was off position. Harness unhooked. Guage lights still on. Wrong harness?

Harness I unplugged had lots of wires. Fairly oval shaped versus round. Harness goes into a square black box about 5" square. I assume that is the Smartcraft electronics. I assume the harness plugged into that is the correct one and that the 5" box it is plugged into is the Smartcraft electronics.

Any further input would be appreciated.
 
If anyone could provide a picture of the harness that gets disconnected, I would greatly appreciate it.
 
Don’t take this wrong but are you certain they are lit up and it’s not just sun light? Sorta like when a car tail light looks on but it is just sun.

Seems very strange.
 
Just looked at wiring schematic for my ‘05. There is a Smartcraft harness connector on the port aft side of engine. There is a resistor in or right near the plug (dash side of connector not engine side). Problem with schematic is that it shows the harness as a single line without showing individual wires. The harness feeds tach, alarm, & big multigauge. Multigauge then feeds speedo. I seem to recall from memory that the harness is blue but can’t be certain. I know this doesn’t help much. If you had access to a spare harness it would be easy enough to plug into engine side and dash (temporarily running straight over the deck) to see if there was a problem with the harness or resistor.

The backlights being on with battery off makes no sense unless the radio preset memory (always hot) got common with the gauge lighting. You could pull the always-hot wires’ fuses (fuse holder for auto bilge and second one for radio memory both near battery switch) to see if it has any effect.

This is a head scratcher.
 
I hear you on strange. It was 9:30PM. Was dark outside. Cupped my hands around each dial to block out what little light there was. Backlights were definitely on in the state that I mentioned above. I am at a real loss.

Marina Service Manager said that the Engine Control Module (ECM) can sometimes take up to 30 mins to go to sleep and that may power the guages. However, that would mean that the ECM has a power source like a battery inside.

Definitely struggling to understand.
 
I will try pulling those always hot fuses next to try to kill power to everything.
 
ECM could have some type of capacitor internally but why it would power backlights is hard to understand. Plus you have other gauge issues. I’ve never noticed my backlights on when I shut the main battery.
 
Chris C said:
If anyone could provide a picture of the harness that gets disconnected, I would greatly appreciate it.
Click to expand...

If it ever stops raining here, I’ll take a picture next time I’m in the boat.

Hopefully Saturday.
 
3D68850A-DBF1-4749-AB8A-844DDD97A6A0.jpeg
Here a picture of the round plug. It’s circled in yellow.

This is on a 2007 240 Sundeck
350 MAG with DTS.

if you don’t have DTS, I can’t say for sure if you will have this exact same plug.
 
Chris C said:
Just bought a 2007 240 Sundeck. Took it out for a long weekend. On 2nd day gauges went out, except for Tach. Tried to reset pushing Mode & - and also shutting off battery, neither worked. Then next day when turned off battery, backlights on gauges stayed on. Anyone have an idea?
Click to expand...

I've also noticed that on my 2007, the gauge backlights don't necessarily turn on when I turn the navigation lights on, and they will be on even if the navigation lights are off.
The navigation light switch will light the dashboard switches when its on.


I've only see the gauge backlights on when it is dark enough outside. It seems to me that there is a light sensor somewhere that turns the gauge backlights on independent of the navigation lights.

I've looked at the wiring diagram but I don't see any light sensor on the digram.

Unlike you, my gauge lights do shut off when the key and/or battery is shut off.
 
Thanks for the follow ups. I really appreciate it. I am sorry that I have been away alot and am just now seeing all the updates.

Very helpful picture. Thank you again. The connector you circled is not the one I pulled. I pulled the more rectangular one above it in the upper left.

Since I could not seem to figure it out, I ended up having a Tech look at it. Was about $100. They said they did a system reboot and it all started working. My guess is that had I pulled the connector apart that you are showing here, that would have done the same thing and fixed it.

I did think about pulling this harness apart as one of my options to try. Guess I was a bit to worried to do that for fear that it may render the boat useless if I messed something up. I didn't want to disappoint my wife and kids while they stood on the dock as I killed our boat for the day :) Our marina is 1 hour and 15 min drive from our house. It is in a Drystack and we are using it for the last time this year tomorrow. With the short season left, I wanted to make sure the boat was not down for the remainder of the season had I messed this up.

However, I greatly appreciate again having this idea. I will definitely try the next time. Since I now have all this great info and know how to fix this next time, I am sure it will never happen again. So it should be permanently fixed now! :)

Thanks again!
 
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