Electric expert needed, Sprinter 2010

[Pedrodasdas]

Hello,

I'm still working on my coachstep with some good and bad success so far.

The stepcoach is wired to the Sprinter ignition switch so when you start your vehicle, if the coachstep is out, it will automaticaly retract.

Presently, I have no power on this wire, ignition on or off.

I have been able to trace the wire all the way back under the driver seat. There is kind of black plastic extension above the fuse panel with 3 connections section. The center one is 12 volts all the time, the one on the right, I don't know. The one on the left has two wires, a full orange that goes to the coachstep and a small green w yellow line that should provide current when the ignition is switch on. My problem is no current on it and impossible to trace back unless untapping all the wires under the seat.

Am I right to think there should be a fuse somewhere between this connection and the ignition ? Any live wire should be fused, no ? If yes, any clue where it is ? Any clue which fuse it could be ?

If anyone go check that connection under the seat, please verify if it is well screw, mine is not tight, wrong bolt used but so little space to work there.

Anyhelp will be appreciated.

Pierre

[bubbles]

I don't have a Sprinter and my MH has a battery control center (BCC) which has an ignition switched output thru a fuse at the BCC. If you have a BCC might check that. If not consider this input moot.

[DaveJordan]

I'm afraid I can't help a whole lot...but here are a couple of thoughts.

First, the wire to the ignition may never be hot. They sometimes wire the switch (in this case, the ignition sensor) on the ground side of a circuit. You might check to see if it connects to ground with the ignition on and doesn't when the ignition is off.

Second, if you need to work on the wiring under the driver's seat you may do yourself a favor by removing the seat enough to get in from above. It's really hard to see what's going on in there when the seat is in place...and, as I recall, removing and reinstalling the seat isn't as difficult as you might think.

Good luck in any case!

Dave

[bubbles]

That's true but if the steps are Lippert or Kwikee they require a 12 volt ignition switch "ON" input to retract steps when the door is closed.

[Larry-NC]

Originally Posted by Pedrodasdas

I have been able to trace the wire all the way back under the driver seat. There is kind of black plastic extension above the fuse panel with 3 connections section. The center one is 12 volts all the time, the one on the right, I don't know. The one on the left has two wires, a full orange that goes to the coachstep and a small green w yellow line that should provide current when the ignition is switch on. My problem is no current on it and impossible to trace back unless untapping all the wires under the seat.

Pierre,
I'm not sure what you're describing, but the part in blue seems to be a plug-in relay. Maybe you could attach a picture. Here are some pictures of typical relays:

They wouldn't run all the current for the step motor through the ignition switch. They would use a relay. Post again if that's what you've found and we can tell you what to test next.

Larry

[bubbles]

Originally Posted by Larry-NC

Pierre,
I'm not sure what you're describing, but the part in blue seems to be a plug-in relay. Maybe you could attach a picture. Here are some pictures of typical relays:

They wouldn't run all the current for the step motor through the ignition switch. They would use a relay. Post again if that's what you've found and we can tell you what to test next.

Larry

The ignition switch input is a logic (12 volts) input into the step controller and not the power for the steps function.

[levoyageur]

méchand problème
si tu trouves la solution, fait nous savoir.

[Pedrodasdas]

Thank you Dave, Larry and Bubbles.

Definitively has to be 12 volts positive. Hed the same problem 4 years ago but solved it when I discover the wire was broken.

This time, no break, Ohmeter tells me everything is good.

Here is a picture from under the seat.

the wires are in the left portion of the three compartments. Definitively MB wire under the orange one.

[Pedrodasdas]

This little box was put there exactly for add-ons. One connected on ignition, the center one full current all time and the one on the right, don't know yet !

[DaveJordan]

Originally Posted by Pedrodasdas

One connected on ignition

OK. If I understand this correctly...the wire on the left in the second picture in your post goes to the step. And the post it's connected to should be hot when the Sprinter ignition is on. Is that right?

Assuming it is, you'll likely need some sort of Sprinter reference document (or online info) about the under seat wiring. And I just happen to have an online copy of the MB "Sprinter Body Builder Information Book" with a print date of May 3rd, 2011.

It describes those three terminals on page 54:

• 1st power with engine running 12V / 10A blue/yellow
• 2nd battery direct power 12V / 25A red/gray
• 3rd ignition power 12V / 15A black/yellow

So your analysis of the first two studs appears to be correct. (Even with their description, I'm not sure what the difference is between the 1st and 3rd studs...)

Unfortunately, this manual doesn't seem to indicate where you'd find a fuse or circuit breaker that might be interrupting power to that first stud.

According to my 2013 MB Sprinter Owner's manual:

The fuse allocation chart and other information on the fuses can be found in the "Fuse allocation chart" supplement.

I found a link to the 2015 supplement here:
https://assets.mbvans.com/Mercedes-B...inter-Fuse.pdf

I took a quick look through that manual, but it will take more study to figure out where that post is fused...

Good luck!

Dave

(Couldn't sleep...)

[DaveJordan]

Originally Posted by DaveJordan

I took a quick look through that manual, but it will take more study to figure out where that post is fused...

So I looked at the fuse allocation chart a bit more closely. Nothing definitive, but you might look at fuse # 12 in fuse block 55/4 and fuse # 23 in fuse block 55/5.

These fuse blocks are accessed from the side of the driver's seat, under the removable plastic panel. 55/4 is the block on the top right, 55/5 is the block on the middle left. The fuses are numbered starting at the top left, so fuse 12 should be the third fuse from the left in 55/4 and fuse 23 should be the 5th fuse from the left in 55/5.

I just looked through the chart for 10 amp fuses and these two looked like they might be possible. (Fuse 12 is listed as "D+, body/equipment manufacturer", fuse 23 is "Electric system: non-MB body")

Of course, we're looking a manuals from several different years so things may have changed! And there may be other fuses and relays involved...

Dave

[Pedrodasdas]

Wow Dave Jordan,

this is what a call a complete answer !

I focus on the running engine for the left post! So far, I have verify only with ignition on ON position, not with the engine running. This will be my next step. I will also verify the right pole, may be I can use this one instead.

Yesterday, I went thru all the fuses with no result. I know fuse 23 is not the one cause I experimented some problem with this one.

Thank you again, people like you make this forum so alive. Stay tuned!

[Pedrodasdas]

Mister Dave Jordan,

May I nominate you for the Genius of the Day !

Exactly as you wrote. The key word was: RUNNING

Plus the fact I had to retight the connection and everything is working as it should now, many thanks.

Now, I'm on the case of the switch on the screen door, I suspect a broken wire. Much easier to find.

CASE SOLVED !