then it's likely not moving enough air, restricting the flow, try removing the shrouding .... why don't you have the engine mounted fan? engine too close?

Bill

Moved over to the Passing Lane

"When we tug a single thing in nature we find it attached to the rest of the world" John Muir
"When we tug a single thing on an old truck, we find it falls off" me
Some TF series details & TF heater pics & Rust-a-holics Unanimous parking lot