I just bought a reconditioned think, runs and looks great—But— here it comes 
Its been reprogramed and clocks on the road at 35, but when I get over 25 the whole display go’s blank, when I slow back down to 25 it comes right back on?
Thinking this might have something to do with controller?
Any ideas out there ??
I have not confirmed anywhere that works on the low speed EV’s, except golf cart places that seem to specialize in certain brands. The Foursom website in Woodburn states they work on low speed electric cars but also says to check with them ahead of time if it is a non Club Car. Might be worth a call-
You may have a cracked or broken magnet in your speed sensor located on the end of the motor. Black plastic piece 1.5" in diameter, held on with 2 screws.
You may wish to contact whomever reprogrammed the controller. I am not as familiar with the Th!nk as I am the GEM.
Daniel