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Auto-retracting step modification
Posted: 4 March 2019 11:35 AM
Subject: Auto-retracting step modification
A posting machine

Posts: 353
Location: Somerset. Frankia i640SD

I have a Project 2000 that automatically retracts when the engine is started (assuming the switch is not faulty but that is another story!). This modification stops the step from retracting if the door is still open.

We had a near accident when leaving a site as I prematurely started the engine just as my wife was about to step out of the van to remove the levellers. Obviously the step started retracting as she was about to step onto it!. I made a modification that prevents this happening which might be of interest to others. I know that Thule makes a step control box that has a "door switch input" which I think does the same thing as this, so if you already have one of these fitted, this mod is not relevant to you.

I added a switch on the habitation door and connected this to the step "auto retract" relay so that it will only be energized when the step is out, the engine is running AND the door is shut. This was quite easy to do as my door already had a small magnet that drives a reed switch that detects when the door is open to give a "Door open" indication on the Ducato instrument panel. I just added another reed switch along side this one (not electrically connected to it) so that it also gets activated by the same magnet when the door is shut. I connected this reed switch in series with the relay coil wiring. The relay coil current is just over 100mA so only needs a small reed switch (most are rated at 500mA).

The other benefit of this modification is that you can still operate the step using the manual switch when the engine is running (with the door still open of course) that you cannot do with the standard wiring. The step will automatically retract when you shut the door if the engine is still running.

Attached is a wiring diagram that I sketched out for my van. Some of the wire colours may differ and some steps may have been wired with the relay terminals 86 & 87 driven from the fridge relay. This modification will still work with this arrangement.

I used male & female spade crimps on the wire ends so you can just unplug the spade crimp on pin 85 of the relay and reconnect it to the new wire to eliminate cutting any existing wires. If you have a large capacitor across the relay coil, you should wire the new switch between this capacitor and the relay coil to avoid high surge currents in the switch. The relay should have a built in diode across its coil to prevent arcing across the switches.


Attachments Step_wiring.JPG (39KB - 2335 downloads)
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