Is J2 the socket for the PIC, or is it going through cables to the PIC
somewhere else?

What are the trace lengths on the loop from Q1 source (ground), to the
nearest bypass capacitor on +12VR, through D5, back to Q1? (Hint: D5 must
be placed at Q1, not at the coil.)

There should be a series gate resistor, particularly if J2 (if it is the
processor, and not a cable) is more than a few cm from the transistor.
Sometimes not even that. 100-1k ohm would be plenty, installed right at
the gate.

Just out of habit, I would specify a BJT for the switch, which I think
saves a few cents and not much else (the series base resistor is
required). Seems unlikely that the coil would fail shorted (so a current
limited switch would be desirable) or generate spikes more than normal
(demanding better spike protection, e.g., RCD snubber).

Tim

--
Seven Transistor Labs
Electrical Engineering Consultation
Website: http://seventransistorlabs.com

"Jay" wrote in message
...
Hello,

I am having a high failure rate on a 2N7000 FET that drives a relay
coil.
Please see the attached jpeg. This gate drive is coming from a 5 volt
PIC18F452 pin 5 (RD7/PSP7) Any thoughts greatly appreciated. Note that
it
will run for quite awhile, perhaps 20 to 30 thousand cycles before
failing
entirely shorted Drain to Source.

Thanks.