Building a heater into rear defroster blower hose

Not an inference from you kid, but a straight up statement:

12vdc production units are designed for RVs and auto usage so failure due to vibration, over temp conditions and burning a vehicle down are taken into consideration in the design.

What I linked has 168 watts at 12vdc probably be running at 12.5v, so about 175 watts and contains a thermal protection circuit.

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Unless you have had one of those heaters apart, you can't say they do contain a thermal protection device. I have in fact had one apart. There is no such device installed.

The DCR on the heating element is 1.73 ohms @ 70f It climbs rapidly to 3.1 ohms at 130f - Which works out to 63 watts @ 14.0v

That would be 63 watts if it could actually see 14v - the 20ga wire in the cord provides additional ballast by warming to the touch quickly. There is a 15 amp fuse in a fuse holder, and it would probably not blow until the cord melted completely - the fuse is cool to the touch while the cord is hot. The damn thing is a fire hazard.

The little squirrel cage blower inside is rated 3.6w, and would probably be inadequate to cool the CPU in an old 386. A six year old kid with a toilet paper tube could blow a better stream of air.

A proper ruggedized ceramic element in the 250w range costs significantly more than that unit.

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