Boat Starts, seems to run ok, gauge cluster not working

[clint888]

Hi all,

 

Update on fixing the boat. Initial problem was as above the gauges stopped working on the dash.

We tested a few items and weren't getting any voltage out of the MMDC to power the gauges.

Here is all the items we checked then the problem we found.

1. Checked all grounding lugs and terminals on the boat. Removed all lugs and cleaned with sand paper then re secured to boat motor and dash ground bar and battery terminals.
2. Tested all the pins on the 36 pin MMDC connecter plug. We were getting 13.2 volts on both power terminal. The MMDC requires both power sources across two sets of pins. One is purple and the other is red and white. Dont confuse the other red and white cable as it is 7 vdc.
3. Replaced the MMDC from medallion. Had to go via linked in and got a contact called Jess Doom she was really helpful. Purchased new MMDC, and all gauges for the boat as we are in Australia and we dont stock oil let alone new 2006 model gauges.
4. Plugged new MMDC in and new gauges. nothing working. Again tested pins voltage and low resistance to ground so no grounding issues. no comms issues either as we purchased the software so cna access all the fault codes and ECU parameters for our boat.
5. Checked all oil switches temp switches as the buzzer for the boat was on.

THE FIX

Finally we decided to fully isolate all wiring from the MMDC to the boat main loom and disconnected all instruments on the 36 pin plug so there was no I/O or grounding back feeding the MMDC. We then spliced the red and white cable which required 12VDC and went directly off the battery. We joined the purple cable and the red white cable together as they bothe rrequire 12VDC. And the gauges fired up and started working.

Traced the red and white cable all the way back to the series of circuit breakers near the drivers side and then tested the circuit breaker. 12VDC unloaded but when loaded with the MMDC and instrument gauges we were getting 5 VDC. Moved the automotive lug to the circuit breaker next to it and the gauges work 100%.

So in saying this if your gauges dont work you first need to know what each core of your MMDC harness does. We spoje directly to medallion and they emailed me a full wiring diagram for my boat.

Check all grounding. Check and isolate each instrument on your boat as it may be earthing out if there is a short. Dont trust your circuit breakers to be working they fail under load. Get a small peice of wire and fuse it with a 2 amp fuse and go directly off your battery.

Spent 2 grand on new MMDC, gauges etc. It was a absolute shi t fault with loads of hours and cable pulling but now we know how the whole MMDC can bus and wiring system work so anyone needs a hand let us know.

2006 malibu wakesetter 247 lsv

[formulaben]

Dude, that suuuuucks.  Thanks for posting, as someone down the road will see this and benefit from your misfortune.

[RedWakesetterVLX]

So yesterday all the gauges running off the MMDC died in my 2000 Waksetter VLX.  They do t power up at key on and gauges do not reset.

I checked the cannon plug and it’s good.

I pulled the gauge face and swapped the 5 pin plug with all the other 5” gauges (speedo, tach, and 4 multi gauge) nothing.  

I don’t have the 2 inline fuses that everyone else has mentioned.  I have one 30amp inline fuse running between the yellow wire and a relay that runs to the MMDC.  I pulled the fuse and it looks ok but I’m going to replace.  I do t not see any other inline fuses running under the dash. I managed to damage the relay so I’m going to replace that too. Next step is to trouble shoot with multi meter and see if the box is shot  is the MDC guide.

Anyone have any idea why I have only one 30 amp inline fuse vs to 2 small ones (7.5a and 2.5a)? I have not heard anyone mention the having the relay between there box either. Below is the picture of the relay I damage.