Also what year and model heater? The older ones worked different then the new all electronics ones.
Where you running it on gas or electric? After 45 minutes both would be hot and need to shut down.
Sounds like something is not working right but need some more info to better help
Current Sunlines: 2004 T310SR, 2004 T1950, 2004 T2475, 2007 T2499, 2004 T317SR
Prior Sunlines: 2004 T2499 - Fern Blue
2005 Ford F350 Lariat, 6.8L V10 W/ 4.10 rear axle, CC, Short Bed, SRW. Reese HP trunnion bar hitch W/ HP DC
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