Did a short job today out to Kalkallo, and on the way home I made it most of the way through the Pentlands before the van abruptly gave up.
Whipped out my laptop and the diagnostics gear (this thing's saved my arse so many times now!), and I'm getting code P1610 "'Voltage Supply' relay switches off too soon (no fault storage possible)". After staring at the wiring diagrams a few times inspiration strikes, and I switch out two of the relays under the steering column. One is very hot to the touch while I'm removing it.
The van starts, but I have no indicators again. In to Mercedes Benz in Ballarat, and I ordered all three relays that are in Australia (apologies if you need one this week). They had one in stock there, the other two have to come from Laverton. I'm having them shipped out as soon as they can. They're also about $60 (!!!) for what appears to be a plain 12V 20A relay with a Mercedes-specific pin out.
I took the one they had, put it in the socket for the engine control, and put the other good one (deduced by process of elimination) in the indicator socket. Everything works, for now. I ordered the other two though, because apparently there's a bulletin for that part - the original spec part is dodgy so they supply a replacement part instead. Figured I'd replace them all now while I have the money.
Old Relay Part: A004 545 29 05
New Substitute Part: A003 542 02 19