Found that the overheat condition was happening only when the unit was working hard to recharge a four battery bank. (that's another story that brought up this fan question...had a short across two wirenuts inside the Xantrex where the AC was wired to it. This happened without a smell we detected or a sound we could hear, so the Xantrex switched over to battery only so we ran on inverter for two days, running the washing machine, two tvs and both fridges and lots of lights before the problem was noticed).
So my batts were down to 11v and needed to be charged now that the
xantrex was repaired. That's when the overheat condition was noted.
The temporary fan worked, so thought up an alternate plan.
I am loathe to have to get the Xantrex out of it's mounting area as doing do would mean having to disconnect all wiring...a lot of it heavy duty. I know because had to cut some of it back to replace the shorted parts.... didn't want to do it all over again.
So, got a 12v computer type box fan and ordered a 95 degree thermal switch off of ebay (3 for about 10 bucks...I can use the others back home). When it's working normally and not having to do heavy charging or inverting, the unit is cool to the touch....in fact it is hard to find a warm spot on the case.
Will power the fan from a nearby 12v basement lamp (left on with bulb removed). Mount the switch on top of the unit at the warmest spot, and clip the fan on the bottom to blow air up thru the unit when it switches on.
Thank you gentlemen for your responses.