Arfa Daily sez:

Not then, I would suggest, a 4.7v zener ... Sounds like it's just a
flywheeling diode and a 1N4007 would do the job just fine. Does the FET
source go to ground ?

The source connects to a flame-resistant (blue), less-than 1-ohm, 1/4w(?)
resistor (red-violet-gold-gold) that measures about 0.5 ohm. (It should
measure 0.27, yes? Maybe candidate for replacement? But maybe it's my Fluke
77's accuracy at that low setting. Resistor doesn't look abused...) The other
end of the resistor does connect to ground.

Many power MOSFETS have a diode internally in that
orientation across from the source to the drain. It gets there as an
integral side effect of the manufacturing process.

Yes, I've read about the need to short out back-EMF when dealing with relay
coils, solenoids, etc.

So, 1N4007 it is.

An after thought... since the diode was cooked (it actually charred the PCB
beneath it) but the resistor and the FET are OK, maybe the diode needs to be
boosted to a higher A rating? Thoughts?

Thanks to all,
--
John English