Temp gauge not registering

[philanum]

I have a 2007 20v MP FI engine. Where once the temp gauge worked, it does not move at all now. It is a 4 part gauge and other 3 gauges work. The attachment on the back is secure. Where woud I find the temperature sending unit? Any suggestion how to diagnose problem?
Thanks

[andrzej77ff]

I am having a similar problem, my temp guage works intermittently. I changed my sending unit and still not fixed. The sending unit is on the housing of the thermostat and has a wire attached to it, I would start there, inexpensive and easy fix. Supposedly if you unplug this wire and ground it out the guage should jump all the way to the right, and that means the guage is OK. I think I may have a bad wire and how to check that is attach a seperate wire to the back of the guage where your sending unit wire is attached and attach the other end to the sending unit when your temp guage is acting up. If your guage starts working right away you know you have a bad wire.

[philanum]

Temp issues

I do not see a wire attached directly to the thermostat housing. Just to the starboard side of the housing is a connection with one yellow and one black wire. It looks like it's attaches to a sensor in the top of the engine. Maybe the 07 motor is different than yours. Any idea which color wire in the connection behind the gauge goes to the temperature?

[andrzej77ff]

The color of my wire is a light brown and where it attaches to the sending unit it has a little boot that slips on a threaded stud on the sending unit. It is on the starboard side but not on top of my motor and it is only a single wire.
Here is a link to a thermostat housing diagram. The water sender is #3

http://www.boats.net/parts/search/Me...ing/parts.html

[bigdaddy_houseboater]

It's likely that it isnt the sending unit, but that's an easy test. It's more likely it is the Medallion Mini MMDC gauge controller. It sounds expensive, because it is. Mine is bad and my tach and hour meter dont work.
Test your sending unit first, as it's only going to cost $15.

If thats not it, go get a second on your house mortgage... cuz Tige is very proud of the MMDC module.