Why does Mercury have a diode on the start wire at the solenoid attached to ground. I don't have a serial number but believe its on all current outboards. When the diode goes bad (shorted) it blows the main fuse.
Why does Mercury have a diode on the start wire at the solenoid attached to ground. I don't have a serial number but believe its on all current outboards. When the diode goes bad (shorted) it blows the main fuse.
Standard practice. The solenoid coil can kickback a high voltage spike. The diode shorts out the spike. Protects other electronic components connected to that circuit.
Originally Posted by Avanti
Damn! I thought I was the only one here that understood that!
Standard practice on most electronic devices to prevent damage.
The start circuit isnt hooked to anything else according to the diagram. The key start position is only energized when its turned to start. When the key is released the wire is dead. So when the solenoid kicks back the spike has nowhere to go. Open circuit. Is there another possible reason for the diode?
When the magnetic field collapse in the solenoid and the core returns to normally resting position a huge voltage spike is created because of the the open circuit. The spike has to go somewhere and that is sent through the positive cable and every thing that is connected to it,
The core has become a very strong magnet and there is very sleight delay on the contacts opening leaving that for current to flow
Last edited by lpugh; 06-11-2021 at 08:51 PM.
Thank You Leon Pugh
I tell you what, 12 volts won't shock you of course, you hold the energize wire to a solenoid and I'll turn it on and off. Don't drop it.
Got it. Thank you for the info.
TMI?
At the very least it protects the ignition switch. The spike will jump the switch contacts if it isn’t clamped. Where it goes from there depends on many things.
De-energizing a coil is how simple gas engine ignitions work to create the spark. The points are the switch.
If you have integrity, nothing else matters. If you don't have integrity,
nothing else matters.
Yeah, and that spike can be upward of 14,000 volts. It will get your attention fast.
No I can handle it.TMI?
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