2015 cargo van rear heater/front heater question

[skz2015]

Hello! My trusty van, new to me in 2019, has a rear blower HVAC system. Last month, I stopped getting heat in the cabin. I was travelling, of course, so I tried to keep going. There were no dash indicators of any issue. No engine light, the engine temp gauge was steady.

When I flipped the control for the rear heat just to see if there would be any change, everything sounded normal (audible fan sound in the rear) but no heat.

I just got my van back from the shop. They found the coolant was ridiculously low from leaking cracked plastic connectors and hoses which were likely original. The front heat works great but turning the rear switch leads to very loud blowing sound in the cabin on the right side. I checked in the rear of the van and that blower was silent.

The shop people suggested that the blower is bad but it doesn't seem logical to me that it was functioning perfectly except that no heat was reaching it and now it's completely silent/dead but whatever is supposed to be finding its way to the back is blasting out the right front vent.

I have not tried much work on this van on my own but I'm willing to try stuff. This just strikes me as something that did not get reconnected correctly. Or maybe a sensor or fuse. I just don't know where to look.

Thank you so much for any help or ideas!