I made a silly mistake when fitting my Propex heater, despite having fitted one to my old van. I connected the power before the control box. The instructions don't make a big thing of this, though if you follow them in order it does cover connecting the control box first. Connecting the power first blows an internal fuse. I called up Propex and they were really good, recognised the problem and sent me out a new fuse for free, that arrived the next day. Unfortunately although I then got lights on my control box, the heater wouldn't run, only the cold fan. The control box did not flash to convey an error message either. Called Propex back and they told me to send back the circuit board from the control box. They sent it back really quickly, having resoldered the connections, but said they didn't think that was the problem. Sure enough, the problem was still there. Next they told me to send back the circuit board from the heater, which I did (they are not difficult to take out, unplug 5 wires and 4 screws). Again they had it back to me within 3 days of me posting it to them, with no charge, and this time all was well. Toasty heating, just in time for a long journey last weekend for my dad's 70th. Obviously having to faff about like this is a hassle, and I think the instructions could make it clearer that the order of connections must be followed, but they did everything you could ask, without charge, to sort me out. The heater is excellent and now I know the customer service is too. Highly recommended.
I blew the fuse in mine exactly the same way you did, power on before I connected the control box. I was lucky though, I changed the internal fuse for one I got from an electronics place and my heater worked.
