Marquis Lancashire electric step problems

Hi, John here. I have a 2010 Marquis Lancashire fitted with a Project 2000 electric step which has just started giving problems. I’ll try to list the symptoms as concisely as I can.
1. The button by the habitation door no longer has any effect, but works fine when removed from van wiring and tested on another 12v supply. The step will retract when the engine starts, as it should, but it extends as soon as the engine is switched off, which it shouldn’t.
2. Sometimes, the step will retract and then immediately extend again all on its own!!
3. If you move the fridge controller from 240v to 12v the step will sometimes retract and immediately extend again. The fridge doesn’t work on 12v with the engine off, only with the engine running.
3. If you remove the fuse from the fusebox behind the drivers seat, the step retracts and the light on the fuse box goes out. As soon as the fuse is refitted, the step extends and the light comes back on.
4. The step light does not work anymore when fitted to van wiring, it works fine when removed and hooked up to a 12v supply.

I’m guessing that there is some type of switch/relay fault but I’m no auto electrician. The problems noted above all started at the same time.
Any help appreciated.
Cheers, John

First we need to know which electrical system is installed? I think in your van it could be either of Sargent PSU 2007, Sargent EC325 of MES?

It’s the Sargent EC325. Everything else appears to be working fine.

The commonality of your symptoms is in the EM50 box that will be behind the drivers seat - could be an overheated fuse caused circuit damage.  The fridge only works on 12v when the engine is running - again controlled in EM50:

[You must be registered and logged in to see this link.]

Thanks for that. I’ll look into it and see if I can see anything obvious and report back

Also worth unscrewing and gently lifting the em40 to check the circuitry on the underside. I had problems with my fridge and although all the fuses were ok the relevant connection on the rear had burnt out.

Just to add to the mystery, I came out to the van last Sunday to find the step had miraculously retracted itself overnight. I tried the button inside the habitation door, still nothing. So I just shrugged my shoulders and drove 60 miles to Hunstanton to walk the dog on the beach. Tried the button again and hey presto, all was working as it should and it still is, a week later!!!

Gotta love vehicle electrics

Not sure if this is relavent to your problems, but the switch on my step was sticking in ever so slightly, enough to stop the Project 2000 from working properly. I removed the switch and shaved some plastic off the side of the housing.
Rob