Hi,

I'm a new hi-lo owner and just started up the heater. It starts up fine as per the instructions, but doesn't come back on once the space is heated up. When I checked the plenum it was hot and the reset button was on the off position. It's almost like there isn't enough return air to cool it off. The problem is worse w/
the bed (couch and dining area) fully in use.

I had the same problem with my heater, the high limit switch needs to be replaced. This bi-metal disc switch gets weak overtime causing the gas valve not to turn-on. When I was replacing this part, I removed the spark ignitor/sensor and noticed it was dirty. I cleaned it with fine steel wool. Also, check voltage & gas pressure to the heater. Good luck, this worked for me.

LES 97 21ft towlite