12v Cab battery volts no current

[argoose]

Hi, after a bit of insight. I went up MH to do a check around. Omni step came down on command. Checked volts for Cab and Leisure, both showed full 13+v on solar.
Exited van the step would not retract. Started van buzzer sounded and step retracted. Step would not come down on command. Tried interior lights on cab battery, bright but dimmed quickly. Ok on leisure battery. Looking at volt meter on control panel. 12+v, but dropping to 2v when operating step switch or lights. Recovering to 12+v when not under load. The only check I have done is voltage at fuse by the spilt charge relay but unable to check load voltage, as I was alone.
I am thinking there is a short some where between split charger and control panel above Hab door Or poor ground.
2005 Ace/swift Napoli on 15 mwb Ducato''.
Any thoughts would be greatly appreciated.

 

[Lee]

It sounds like one of your batteries are flat, check both with an meter, without any solar, ie in the dark or the solar disconnected.

 

[molly 2]

Check battery leads are clean and secure

 

[argoose]

It sounds like one of your batteries are flat, check both with an meter, without any solar, ie in the dark or the solar disconnected.

Thank you for reply. I've Isolated solar with breaker. Lights work on leisure battery. My first thought was bad cab battery, about 12 years old. Replaced cab battery with new. Symptoms are the same.
Unfortunately the omni step does not get power from leisure battery, It is purely cab powered. needs to operate before and after entry or exit from van.
I am of up to storage with torch and working clothes tomorrow. I will check out that the 12v leisure side is working. But I feel that it is confined to the 12v cab supply side.

 

[argoose]

Check battery leads are clean and secure

Hi thanks for reply. New cab battery on today. terminals tight and corrosion free. My thought was old tired battery. New battery same symptoms.

 

[marchie]

Thank you for reply. I've Isolated solar with breaker. Lights work on leisure battery. My first thought was bad cab battery, about 12 years old. Replaced cab battery with new. Symptoms are the same.
Unfortunately the omni step does not get power from leisure battery, It is purely cab powered. needs to operate before and after entry or exit from van.
I am of up to storage with torch and working clothes tomorrow. I will check out that the 12v leisure side is working. But I feel that it is confined to the 12v cab supply side.

Is the step operating freely? If the battery returns 12v+ after step operation, grit, corrosion etc could be causing a drag and therefore an excess load. I think David @wildebus had similar problems about 12 months ago, and a clean, spray with PTFE +[?] replacement of lost ball bearing sorted out the problem

Steve

 

[argoose]

Is the step operating freely? If the battery returns 12v+ after step operation, grit, corrosion etc could be causing a drag and therefore an excess load. I think David @wildebus had similar problems about 12 months ago, and a clean, spray with PTFE +[?] replacement of lost ball bearing sorted out the problem

Steve

Hi thanks for reply, I will drown it in GT 85 tomorrow and check. But the same symptom occurred when turning the internal LED roof lights on. And step came out ok and retracted with engine start up. Then stopped operating. New cab battery is the same. Van starts on the button. Before and after operating step. So I'm thinking engine earth, battery and battery connections are good.
Would a test light be more effective at tracing the fault, as there is voltage present but no current?

 

[wildebus]

Is the step operating freely? If the battery returns 12v+ after step operation, grit, corrosion etc could be causing a drag and therefore an excess load. I think David @wildebus had similar problems about 12 months ago, and a clean, spray with PTFE +[?] replacement of lost ball bearing sorted out the problem

Steve

Longer than 12 months ago and different effect, but worth mentioning In my case, a bolt had rusted up stopping the movement of the step mechanism and the motor would cut out due to excessive load. I didn't notice (or remember?) if the voltage had dropped but the result was the step would not come out. simply loosening a bolt got the step working in and out again so allowed me to see what/where I needed to fix.


Voltage drops and outages are a tricky one to troubleshoot remotely, but what I strongly recommend is taking a logical approach rather than a scattergun checking random stuff and document at each stage/test what was tried and what results were seen ref voltages etc. so you can refer back rather than relying on what you think you saw.
And when checking voltages, check at the battery but also check at the other key places - Hab fusebox for example.

 

[argoose]

Longer than 12 months ago and different effect, but worth mentioning In my case, a bolt had rusted up stopping the movement of the step mechanism and the motor would cut out due to excessive load. I didn't notice (or remember?) if the voltage had dropped but the result was the step would not come out. simply loosening a bolt got the step working in and out again so allowed me to see what/where I needed to fix.


Voltage drops and outages are a tricky one to troubleshoot remotely, but what I strongly recommend is taking a logical approach rather than a scattergun checking random stuff and document at each stage/test what was tried and what results were seen ref voltages etc. so you can refer back rather than relying on what you think you saw.
And when checking voltages, check at the battery but also check at the other key places - Hab fusebox for example.

Thanks for reply, I have a plan to check voltage at pin where it connects to the AC85 control panel, then work back from there, or forward depending on result.

 

[wildebus]

one thing to check ... you mentioned about step? is the fridge working ok on 12V when the engine is running?
Typically on a british van there is a lot of shared circuitry on the step and fridge and they split off with a couple of relays, and also - assuming it is still as built - the split-charge circuitry where on a 2005 van, these will often be under the bonnet.

 

[argoose]

one thing to check ... you mentioned about step? is the fridge working ok on 12V when the engine is running?
Typically on a british van there is a lot of shared circuitry on the step and fridge and they split off with a couple of relays, and also - assuming it is still as built - the split-charge circuitry where on a 2005 van, these will often be under the bonnet.

Thank you for the reply. I will try tomorrow . The step and fridge are fed of the same fuse, by the split relay, bolted to the scuttle. But that is the auto retract when engine started. Which worked to retract the step after the switch didn't work The switch feed is from a fuse in the same block. Both feeds pass the control panel, above the door. Split to control panel and carry onto switch relay situated by fridge in door way.

 

[wildebus]

Thank you for the reply. I will try tomorrow . The step and fridge are fed of the same fuse, by the split relay, bolted to the scuttle. But that is the auto retract when engine started. Which worked to retract the step after the switch didn't work The switch feed is from a fuse in the same block. Both feeds pass the control panel, above the door. Split to control panel and carry onto switch relay situated by fridge in door way.

Something to bear in mind ... the control panel above the door is just that - a control panel. You can turn things on and off from there, and it might report voltage levels via meter, number or LED lights, but it is very much a control level of output in terms of current i.e. VERY low.
There is never an absolute and it is potentially feasible for a panel to create voltage problems (hey, anything is possible!), but if you are seeing a low voltage on a step when trying to retract or extend it, say, then the control panel will not be the issue. Maybe if you are pressing a button on the panel to do something and it is not happening, then the panel could be the issue as it is not sending the control to the relay to energise, but you won't get the kind of wiring to power a step going through a control panel

 

[MERL]

Sounds like you have a high resistance contact (something not making a proper contact) somewhere between the starter battery and the circuit supplying the step. Usually corrosion. Can be a swine to trace. Connect the neg meter lead to the starter battery and then measure voltage at various points along the circuit UNDER LOAD ie with the step energised and eventually you'll find a connection point that should read similar voltage to the starter battery but the voltage is actually well down due to the bad connection. Another member had a similar issue a few weeks back with his B2B, that was a corroded connection onto an inline fuse that wasn't obvious because it was enclosed in heat shrink tubing.

 

[argoose]

Something to bear in mind ... the control panel above the door is just that - a control panel. You can turn things on and off from there, and it might report voltage levels via meter, number or LED lights, but it is very much a control level of output in terms of current i.e. VERY low.
There is never an absolute and it is potentially feasible for a panel to create voltage problems (hey, anything is possible!), but if you are seeing a low voltage on a step when trying to retract or extend it, say, then the control panel will not be the issue. Maybe if you are pressing a button on the panel to do something and it is not happening, then the panel could be the issue as it is not sending the control to the relay to energise, but you won't get the kind of wiring to power a step going through a control panel

Yes panel is just a few switches in a piece of metal. All three feeds go to it. Checked for power no current on permanent cab live.
Update. Visual check of loom showed only one scuff mark . Removed outer conduit. No marks on wires. I tried pin testing along loom first site under hab by exhaust. Gave current. Checked step, step works as it should but no lights. Argh! lights and step now work, shoot me now.
Definitely short from lights to step.
Time to wiggle and pull bits.

 

[Nabsim]

On mine if I press the out button when the step is already out I get a big volt drop, same for the in when its in. Not sure if I used to get that before I rewired it to do away with the PCB control box it used to have. So in my case a stuck step would give the drop although OP step works when engine running.

 

[argoose]

Update. Step working, lights work on cab and hab battery. Cannot check anything now, as it works.
I think I got a bit hung up on lights dimming . That was the load side of solar being pulled down.
I disconnected all electrical joins under bonnet, sprayed with electrical contact cleaner.
I pin probed wire close to engine, under van, had 13v. Before probing further I checked step. It worked. Could have been damp/ dirty connection.
If it is fixed great, if not I've got a base to go from.
Many thanks to all who took time to help and guidance.

 

[MERL]

Yes panel is just a few switches in a piece of metal. All three feeds go to it. Checked for power no current on permanent cab live.
Update. Visual check of loom showed only one scuff mark . Removed outer conduit. No marks on wires. I tried pin testing along loom first site under hab by exhaust. Gave current. Checked step, step works as it should but no lights. Argh! lights and step now work, shoot me now.
Definitely short from lights to step.
Time to wiggle and pull bits.

I don't see how it can possibly be a short circuit unless you're using the wrong terminology?
A short circuit means power is getting to where it shouldn't be so two wires touching that shouldn't be. Open circuit is a break in the circuit (or the circuit is open when it shouldn't be). Unless I've completely misunderstood what's happening you have a connection that's intermittent between conducting properly and conducting slightly. Just a bad possibly corroded joint somewhere.

 

[argoose]

I don't see how it can possibly be a short circuit unless you're using the wrong terminology?
A short circuit means power is getting to where it shouldn't be so two wires touching that shouldn't be. Open circuit is a break in the circuit (or the circuit is open when it shouldn't be). Unless I've completely misunderstood what's happening you have a connection that's intermittent between conducting properly and conducting slightly. Just a bad possibly corroded joint somewhere.

My thought was if wire was damaged and when load applied current strong enough to arc to ground or ground via another wire.
Hopefully it was a high resistance connection and sorted.
Which ever way, as it's now working I'll leave unless it fails again.
Thanks for reply.

 

[Tezza33]

On mine if I press the out button when the step is already out I get a big volt drop, same for the in when its in. Not sure if I used to get that before I rewired it to do away with the PCB control box it used to have. So in my case a stuck step would give the drop although OP step works when engine running.

I also get that on our Hymer with a double step, if the step is already out the volt meter on the panel drops to zero, the same if it is in

 

[MERL]

My thought was if wire was damaged and when load applied current strong enough to arc to ground or ground via another wire.
Hopefully it was a high resistance connection and sorted.
Which ever way, as it's now working I'll leave unless it fails again.
Thanks for reply.

High current wouldn't cause that to happen I'm afraid. A pound to a penny pt'll be a dodgy connection and it'll be fine until it's not just like every intermittent fault . At least you've got the option to start the engine to get the step to retract. Good luck