MasterW Posted August 15, 2020 Share Posted August 15, 2020 I have a single step unit fitted to my motorhome and it has started some strange behaviour. The step operates both up and down but when retracted it stops ok, then clunks twice before settling. when extended it clunks 3 times before settling. This action is only evident when on battery power. When on mains it performs faultlessly. Anybody had this problem before...? Link to comment Share on other sites More sharing options...
Tracker Posted August 15, 2020 Share Posted August 15, 2020 We had similar issues with these steps on several vans over the years. It usually only happened when it was very wet, especially after driving in the rain and they always cured themselves as they dried. I took several of them them apart and cleaned and dried them all and their contacts without ever finding what the fault was. The step is 12v powered and as we never used mains hookup I can't comment on that aspect. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted August 16, 2020 Share Posted August 16, 2020 As the step does not exhibit this behaviour when the Hymer is ‘on hook-up’ (when, presumably, the motorhome’s on-board battery-charger will be running) it’s reasonable to assume that the lower ‘off hook-up’ voltage of the battery powering the step is the cause. If the step has had no maintenance since 2015, it should benefit from the type of attention mentioned by Tracker. There’s also (I suppose) the possibility that the ‘problem’ lies with the battery not the step. (You haven’t said whether the step has always done this clunking thing, or has just started to do it.) Link to comment Share on other sites More sharing options...
Keithl Posted August 16, 2020 Share Posted August 16, 2020 Does your step draw its power from the starter or leisure battery and what is this battery voltage when the step clunks and you are not on EHU? Your battery(ies) may be past their sell be date! Keith. Link to comment Share on other sites More sharing options...
chasm Posted August 16, 2020 Share Posted August 16, 2020 Your step is almost certainly powered from your leisure battery and its operation will be controlled by a window winder circuit board. The step operates just like a car window i.e. keeps traveling until it meets resistance and causes a spike in motor current. The operation of the circuit may well be sensitive to a low supply voltage, which supports the comment that the battery may be the problem. It's worth checking the connections to and from the operating switch to make sure they are clean and firmly attached. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted August 16, 2020 Share Posted August 16, 2020 It would be worth checking what happens immediately after the motorhome is disconnected from the mains hook-up. If the step's operation does not 'clunk' then, but does clunk after the vehicle has been off hook-up for several hours, the battery's reduced voltage-state will be the prime suspect. Link to comment Share on other sites More sharing options...
MasterW Posted August 16, 2020 Author Share Posted August 16, 2020 The problem does not appear to be so simple as low battery voltage. The Motorhome has been on EHU for 20 hrs and then disconnected. Two hours later, the Hymer control panel showed 12.7Vdc for both starter (95Ah AGM) and habitation (2x 95Ah AGM). The actual terminal voltage of habitation battery, measured with a DVM was 12.85Vdc. I therefore have assumed the starter battery also has a similar terminal voltage because the Mercedes Sprinter chassis has the starter battery buried under the passenger floor and not so easy to access. However, this is irrelevant because the step is definitely powered from the habitation battery. I have isolated the habitation batteries to check. With these battery voltages as described, the problem is still apparent. it is however, still probable that the higher voltage applied by the battery charger when on EHU is the reason why this only happens when EHU is disconnected. My problem is to locate where there is sufficient volt drop on the step motor or control system to create the problem. The problem has appeared once before and seemed to 'disappear' after I brought it to the attention of the dealer pending a service but they did not carry out any investigations because it was not evident during the service visit. I am trying to understand how this volt drop can cause the clunking issue and why it is so specific in the number of 'clunks' both up and down. Does anyone have a circuit diagram for these project 2000 steps or how Hymer wire them up..? Link to comment Share on other sites More sharing options...
BruceM Posted August 16, 2020 Share Posted August 16, 2020 Might it simply be that the step needs re-lubricating and is currently struggling to complete its final opening/closing phase whilst being driven by the slightly lower voltage of the battery verses whilst on EHU? I can well imagine a dealer in similar circumstances giving the mechanism a generous squirt of lubricant to see if it sorted the matter out for you. Link to comment Share on other sites More sharing options...
MasterW Posted August 16, 2020 Author Share Posted August 16, 2020 Been there done that, but I see the logic, I will try again. Will start a list 'things to try'. I need to get a good idea of how the limit system works. Not sure whether it works with simple limit switches or as chasm suggests, it works by current-monitoring the motor current when asked to deliver more torque. Neither seem to explain why it very specifically 'clunks' twice on the up and three times on the down. Either way, after the clunks, the step comes to rest Ok. Link to comment Share on other sites More sharing options...
MasterW Posted August 16, 2020 Author Share Posted August 16, 2020 Are you sure the step position limits are controlled by torque monitoring like a window winder motor.? If so what does the switch do where the step comes to rest? It does seem very difficult to find any tech data on these steps. Link to comment Share on other sites More sharing options...
MasterW Posted August 16, 2020 Author Share Posted August 16, 2020 My Hymer manual specifically warns against lubricating the step because grit and dust adheres to the grease and will damage the step...!!! Is this the problem where dealers lubricate the pivots...!!! The plot thickens... Link to comment Share on other sites More sharing options...
plwsm2000 Posted August 16, 2020 Share Posted August 16, 2020 The Project 2000 step (and I think the Thule equivalent also) just contains a motor and a limit switch. All the other control wiring should be inside the van but will vary depending on the manufacturer / installer. I listed some variants in this thread [url=] https://forums.outandaboutlive.co.uk/forums/Motorhomes/Motorhome-Matters/2003-Bessacar-Omnistep-not-retracting/54659/ [/url] I sketched out the wiring on my van below. I added another switch that disables the auto-retract function if the door is still open. The standard wiring with auto retract relay will not have this switch (replaced with a direct link) From what you describe, my guess would be that your step mechanism is a bit clogged and requires more torque (therefore more current) at the ends of its travel. Your EHU / charger will give another volt or so, so the motor runs slightly faster and overcomes this extra load. About once a year, I degrease the mechanism and then use a PTFE based dry lubricant which doesn't pick up road muck quite as much Link to comment Share on other sites More sharing options...
Derek Uzzell Posted August 17, 2020 Share Posted August 17, 2020 MasterW - 2020-08-16 7:05 PM My Hymer manual specifically warns against lubricating the step because grit and dust adheres to the grease and will damage the step...!!! Is this the problem where dealers lubricate the pivots...!!! The plot thickens... You could do as just suggested and try a ‘dry’ lubricant like this https://wd40.co.uk/specialist/high-performance-ptfe-lubricant/ Link to comment Share on other sites More sharing options...
MasterW Posted September 11, 2020 Author Share Posted September 11, 2020 Thanks all who responded to my step problem. Motorhome is now back from storage and undergoing further investigation. All pivot points have been thoroughly cleaned and relubed with a PTFE based spray. I now need to wait for the battery voltage to drop because the journey home has bolstered the battery voltage, high enough to stop it happening. Will let you all know the result once I have reduced battery voltage. Clunking was still present before the journey home. Link to comment Share on other sites More sharing options...
MasterW Posted September 12, 2020 Author Share Posted September 12, 2020 So of a 'b' ,...the step still clunks even though the battery is at 12.7Vdc. Soon as I connect the mains it does not clunk. Testing immediately after mains disconnection it does not clunk but after a number of goes, the clunking starts again. Perhaps I should remove each of the pivot points in turn, clean again and not tighten up quite so tightly. It happens on both the up and down movements. its as if the control mechanism is making double sure that is has got where it was going...!!! Can't be a problem with the microswitch because that is not engaged on the down stroke. Any other ideas would be very welcome. Going away on 17th September for couple of weeks so have a few days yet for further investigations. Link to comment Share on other sites More sharing options...
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