Background:
2008 F350 6.4 diesel
Rebuilt 140k currently @ 160k
all the deletes and H&S minimax
runs great....truck was professionally built by Diesel Performance Shops in Chicago, pulls at 18 mpg @ 65 and 22 mpg empty

ok hit the remote start, heats up when I come out, rolling through the county roads, heats up ok, get onto the freeway and no heat at all. come off freeway, heat comes back a blazin!

I just figured out what you guys are talkin about with the "puking" thing and mine did that, but I thought it was cause I just filled it till it was full, but now I wonder if that is part of what ever this problem is...programmer is saying i am between 180 and 197 most all the time, rarely ever goes over 200 even puling a trailer...

It doesnt seem to be electrical casue of the when the heat is working, it will adjust as it normally would....

could it be a matter of air flow? Like the old cardboard behind the grill...

 

maybe try a winter front or cardboard for temporary to see if it helps

 

Mine starts putting heat out at around 120 degrees, not hot, but warm, so if your at 180 and not getting heat something is amiss. What's the temp while your on the freeway.

 

could you be having issues with the outside temp sensor and the climate control?

 

Good thought, I had to move mine when I got my winter cover.