Dont rule out cold air coming into cab from leaks/weather seals (old rubber gaskets deteriorated, gas pedal foam rotted, hole in front FW near drivers side radiator for cables, heater box been rebuilt with new seals ?)... etc !

Too test for them drive around and feel in the areas for cold air.

Hope this helps...
Sean G My 87 Syncro leaks like a sieve ;-(

    On Tuesday, January 2, 2018, 12:12:01 PM MST, ddbjorkman@verizon.net <ddbjorkman@VERIZON.NET> wrote:  
 Ford battery died and the Bus (Vanagon) has been put into extra service.  Always starts right up, hope I didn't put a whammy on myself with that.  Well, it's into the single and low double digits here in New England and I have noticed the Bus has a hard time maintaining heat to the interior.  My temp gauge sits on the lower edge of the red light.  It takes the normal 5 + minutes driving to warm up enough to move the gauge far enough off bottom to turn the heat on at all.  I am considering constructing some sort of bra to go over the upper grille to decrease air flow over the radiator.  First I thought  I might post this question.  Is this normal in the frigid cold?  Have others experienced this?  Could it be a malfunctioning thermostat?  Does someone make said bra/cover?  I await your reply.

Dave B.