There are three wires going to the DESS post
- White/Gray
- Black/Yellow
- Black
The black wire is ground. The other two wires use the black wire as common.
Here is what happens when you put a key on the post. There is a small reed switch in the post that connects to the black/yellow and black wire. The key has a magnet in it, so it closes the reed switch, effectively shorting the black/yellow and black wires together.
This turns on the MPEM. It begins sending out a signal on the White/Gray wire. The center post of the DESS post is connected to the White/Gray wire, and when you put the key on, it makes contact with both the center post and the ring on the post, which is connected to the black wire (ground) This signal "turns on" the key, and it sends the serial number of the key to the MPEM over the White/Gray wire. The MPEM reads this serial number, and if it matches one of the key serial numbers stored in memory, it activates the MPEM which sends out the two beeps. Once this happens, the key circuit is shut off. It no longer has any function, except that the magnet is needed to keep the MPEM alive. The short between Black/Yellow and Black must always be present to keep the ski running.
A lot of times I see recommendations to clean the key, for people that have problem with the ski quitting while running. This is inappropriate advice; cleaning is only recommended if the ski will not start.
Any break in the electrical signals will shut the mpem down until its re-armed. Non-techs have used the olhmter probes into the female or
holes the amp pins fit into, and that enlarges them. Then if no dielectrical grease, the pins develope corrosion.
So, I take it that all guages shut off along with the motor when this happens ? If not, it is fuel related, not electrical.
If you detirmine it is electrical, open and clean every connector and secure them well. If it has a coil box, be sure it is dry inside the box.
Interaction of the starter and the flywheel eventually degrade and the small metal particles find their way into the Stators, and electrical
havok begins interuption of signals. Inspect every 4-5 years, clean, vacuumn, and install a new cover seal.
Bills86e
