Mover Fault

[Beehpee]

Hi all, lovely weather for all caravanners and campers eh, I went away last weekend and at the outset had a problem with my mover, I hooked up without it and managed ok on arrival but it made me determined to either get it fixed or have a new mover fitted as I find reversing a pain in the posterior, I contacted Gary at arc but movers not being his chosen area of expertise he put me on to another repairer, haven’t used this person yet but was pleasantly surprised by outcome of a call to Truma who said to send the box to them and they would test it FOC and let me know if it is repairable, hopefully I’ll get a reply in the coming week and I’ll update you on how my dealings with Truma progress.

BP

 

[Woodentop]

One thing often overlooked as the battery in the remote on its last legs. Operational indication is that the van doesn't move or moves a foot or two and stops. Visual indication on the remote (well, Powrtouch at least) as that all of the LEDs against each button light up simultaneously.

 

[Beehpee]

Remote batteries brand new and tried 2 sets to be sure, on the truma you have 3 lights green, amber and red, green all ok, amber low power and red fault refer to service, it is actually coming up with amber but I’ve proved that both remote batteries and leisure battery are perfect, however with both wheel motors disconnected when I press remote I have 13.2 volts going in to the control box but only 9.45 volts coming back out on motor plugs, there are 6 relays on the PCB and I’m pretty sure it will be a burnt out or partially burnt relay, had I been able to source the exact same relays I would have changed all 6 as my first course of remedy, I could probably have used different relays but with truma offering a free test of the box I felt it prudent to go that way first, I’ve got exactly 4 weeks till the van is going to be used again so time for truma to diagnose and if all else fails get a new mover fitted, with this additional info if anyone has any other suggestions I’d be glad to consider them.

BP

Ps leisure battery is new 110ah which worked the week previously and when it failed my first thought was dodgy new battery, local caravan dealer gave me another new fully charged 110ah battery with same outcome

 

[Woodentop]

The 9.45 volts may be correct as it is the way your meter is reading it that is 'wrong.'
When the mover is working you will have heard a whistle? This is the pulsing supply being sent to the motor - a system known as Pulse Width Modulation. Changing the ratio of the 12V on and off times in the waveform changes the speed at which the caravan moves. The motors are what is known as a stepping motor - exactly the same technology as used on the hard disc drive in your computer or the disc drive motor in your CD player. Doing the same with reverse polarity (what the relays are for - usually) changes the direction of motor rotation. Because the power is being pulsed the meter will not read the peak levels correctly. The only way you can be sure is to use an oscilloscope.

 

[ProfJohnL]

Hello Woodentop,
I totally agree with your description of the controller producing PWM output which many multi meters will find difficult to resolve accurately., But where I think you may have made a couple of incorrect assumptions.

Many on the more recent caravan movers use a controller that produces a soft start to limit initial current draw. This might give a reduced voltage reading at the controller's terminals, It could also be a controller that uses PWM output.

The other point, Ill be honest ans tell you I have not done any recent research into caravan movers, but as far as I am aware, none of the manufacturers use "stepper motors" the use brushed dc motors with a reduction gear box, which PWM current can provide effective speed regulation, and still provide the motors maximum torque even when running at slow speeds.

Realistically a stepper motor would be over kill for what is essentially a very basic function ideally suited to DC motors.

 

[Beehpee]

Mover all sorted, truma did the test which came back with no faults, checked every bit of wiring to the mover and finally found that previous owner who I’m pretty sure must have fitted the mover as a DIY job had joined some cables using crimp connectors and although they were making contact there was more of the strands out of the connector than in, to be sure I replaced all cable runs from battery to control box including new battery terminals and new cables from control box to each of the motors, all now working as it should, glad it’s sorted as off for a fortnight break in 2 weeks time so would have been a new mover required.

BP

Ps Truma tested box completely free of charge including a retest when I said they must have missed something.

 

[Kevin2306]

Well done BP, I really dislike crimped connectors for this reason (especially the scotchlock ones)
glad its sorted.

Kevin

 

[ProfJohnL]

Well done BP, I really dislike crimped connectors for this reason (especially the scotchlock ones)
glad its sorted.

Kevin

Strictly speaking Scothlocks are not crimp connectors, they are Insulation displacement connectors.
(IDC). They can be very effective, but if the wrong type or gauge of wire is used they can fail.

Crimp connectors when fitted correctly do provide very good connection reliability, but again if they are bodged then they can be very unreliable.

 

[forester08]

I have lost count of how many time when looking for electrical faults on customers vehicles it has been scotchlocks at fault.