Thanks for all your replies. Good ideas, all. Yes, I should have said "trips the breaker" rather than "blow a fuse". The garage and wiring are only 6 years old, but the outlet has gotten used every night for over 4 years so that could well be the culprit. Your advice gives me a good place to start.
If you do track it down to intermittent broken wires near the EVSE's plug (
not the wall receptacle), it's pretty simple to replace the plug. Just be aware that there might be a couple extra wires in the plug for a thermal switch (for safety). You can cut the EVSE cable a couple of inches from the old plug (assuming the bad part of the old cable is between there and the old plug). There's not a lot of cable to work with there, and you'll need enough for the new plug connections. Of course, do this when the EVSE is
not plugged in. Trace the three (HOT, NEUTRAL and GROUND) power connection "prongs", and note the wire colors they connect to on the cut-off end of the old plug. (You might need a cheap ohm meter to do this, and one of them might be an intermittent connection.) These three wires will need to be connected to their respective prong locations on the new plug. If this task seems too daunting, let me know, because I can pull the housing off of the plug I put on my Honda OEM EVSE to use on 240V, and tell you the wire colors. Unfortunately, the AC-in cable appears to be molded on, and not serviceable, unlike the J-1772 cable end, which is held with a screw.
If there are two more (unconnected) wires in the old plug's cut-off cable end, these likely go to the thermal switch. In order for the EVSE to work, it needs to think that the thermal switch is connected and working. On EVSE's I've worked on in the past, leaving them open (not connected to each other, or anything else) was all that was necessary, after replacing the plug. (On it, the thermal switch probably shorted the two "extra" wires together, signalling the the EVSE that the plug is
hot.) I put a dab of "liquid electrical tape" on the end of each, to seal them off from shorting to anything else (or each other) in the new plug.
Good luck, and let us know what you find.