Heres a good website for you. You can download all the manuals faults etc....
https://www.butlertechnik.com/technical_library/air-heaters-d4
The problem with that site is all the manuals are blurred. And my set up aint listed. It seems many of these early units where almost custom built for certain truck makes, boats or buses. The variations in wire colour, ecu number and loom configuration are mind blowing.
A fantastic site has been done by a varnish company of all things. Much more DIY oriented and easier to digest but I have been researching most available sites for a week hoping to get this one up and running when it arrived. No rush as with most of my Landy projects but it would be nice to get it going before the ice. Maplins in the morning :D

http://www.letonkinoisvarnish.co.uk/Index.html
 

Similar threads