Caravan mover troubles...

[Harry Bloomfield]

Thinking aloud.....

Moving the caravan today, the mover showed it had a bit of an issue, so now I am trying to diagnose it 'at a distance' from the obvious symptoms, before delving in...

It is run from the 12v leisure battery, via wireless remote control. It drives the tyres via rollers, driven by two heavy duty motors, one to each tyre, which have to be manually engaged, against the tyres. It's not a soft start, rather the 2 motors are powered by 4x Omron relays, two forward, two back. A 5th HD relay, is the master relay, which powers the entire system. The master relay is turned on via a power button, on the remote. On pressing the power button, you hear the master relay click on, then it goes through a rapid sequence of testing the other 4 relays operate, and none of them are suffering welded contacts, or it shuts back down and shows a fault condition.

Now for the problem - After pressing the power button, I hear the diagnostic sequence, then sometimes all works as it should. Other times, the master relay reopens, then closes and runs the diagnostics again, then a random few seconds later - again, and so on repeating. I don't need to touch the power button, for it to do this. When it reacts like this, if I try to drive it, it drives stop start. When it doesn't do it, it drives absolutely fine.

The behaviour is similar, whether the rollers are engaged to the tyres (under load) or not.

It's not a wireless remote problem, because if I go out of range, it just switches off the drive relays. Leisure battery shows 13v, and not much less when powering the motors. Remote has a new good PP3.

I'm thinking to get the PCB out, and on the bench, powered with 12v, then check that master relay's coil is getting close to 12v, and the relay coil is good. I don't have a circuit for it. Has anyone got any other suggestions for this intermittent behaviour?

 

[jj4091]

Bad earth connection?

 

[ebee]

Well if its on rubber tyres then probably no earth connection at all. Might have a bad chasis connection though

 

[jj4091]

Well if its on rubber tyres then probably no earth connection at all. Might have a bad chasis connection though

I did not mean mains earth when he said it ran off his leisure battery. I am not sure if modern caravans use chassis or take live and neutral to each component. Bad earth connections are often a problem on the old vehicles I have.

 

[Harry Bloomfield]

I did not mean mains earth when he said it ran off his leisure battery. I am not sure if modern caravans use chassis or take live and neutral to each component. Bad earth connections are often a problem on the old vehicles I have.

They use a wired +ve and -ve throughout. Thanks, but no, it's nothing as straightforward as that.

 

[jj4091]

As you suspect possible dry joint on pcb then. Seems like a lot of info here https://www.google.com/search?q=int...YChigAcICBBAhGBWYAwCSBwQzMi4z&sclient=gws-wiz

 

[Harry Bloomfield]

...and, sorted - or so it now seems....

I managed to track down the spare control pcb, the one which had a fault - appeared not to respond to the remote control at all. Just in case I needed spare parts. Removed the controller from the caravan, got it on the bench, and connected to a 12v PSU, for further tests.

During the 'further tests', it was straight away bringing up a fault, that it was not 'seeing' the motors connected to it - well there were none. It would though at least reproduce the fault I was concerned with - the shutting down and restarting. No obvious pcb faults, so levered off the relay covers, starting with the main 60/80 amp ones, as they seemed the most likely ones to cause the problem. There were 6 relays BTW, not the 5 I suggested earlier, two main 60/80 amps, and 4x 40/60amp. To the naked eye, the relay contacts looked absolutely fine. So I folded some white paper up, and inserted that between the contacts, closed them, and pulled the paper through. It came out with a bit of black on it, so I then cleaned them up with a diamond nail file, and blew the dust out.

A second test on the bench, failed to reproduce any problems, so I called it fixed. My guess on what was happening.....

Press the 'power button' on the remote, it engaged the main relays and ran it's diagnostic tests, then was supposed to sit and wait for other button presses. What was happening, was the main relays were engaging, the bit of dirt on the contacts was causing some voltage drop, the unit sensed the voltage was too low, and so shut the main relays off.

 

[ebee]

I did not mean mains earth when he said it ran off his leisure battery. I am not sure if modern caravans use chassis or take live and neutral to each component. Bad earth connections are often a problem on the old vehicles I have.

I was being frivolous, I did assume that you didn`t really mean earth but rather chassis used as a return instead

 

[jj4091]

I was being frivolous, I did assume that you didn`t really mean earth but rather chassis used as a return instead

Sorry your frivolity went over my head, but I was not being critical.

 

[Harry Bloomfield]

Well, that worked for a while, then started flashing a continuous fault on it's LED. A few years ago, I bought a complete spare mover, motors, all the mechanical hardware, remote control, and the control box unit - the later being sold as faulty. All the same model, except slightly updated.

The control unit, did turn out to be faulty - despite setting it to pair with a remote, it fails to pair. It uses a AM-RRQ3 433.9Mhz receiver, paired with a 16F819 pic, used as a decoder. Which is as far as I got with reverse engineering the input end of the control pcb.

At the output end, it has six heavy duty relays, driving the two 12v DC motors. One change over relay per, motor terminal, with the common to the motor, NC all go to -ve. All terminals to -ve, means the motors are DC braked.

The NO relay terminals, go to two NO master relays, wired in parallel, then to the +ve. I think the idea is it sets up which of the above four need to close, then the two master relays share the wear and tear of making/breaking the actual current. It checks the relay contacts have not welded up, with every operation, and prevents any further movement if any have.

Idea is - remotely energising one of the 4 motor relays, drives the motor one forward, power the other of the pair, drives it in reverse.

 

[Rodders53]

Make and model of mover?

Also asking for help and advice on somewhere like Caravan Talk might be sensible?

https://www.caravantalk.co.uk/community/forum/72-caravan-motor-mover/

 

[Harry Bloomfield]

Make and model of mover?

I'm not absolutely sure of the model, the model numbers were rather confused, but an early Truma/Carver.

Last night, on my second unit - I managed to check the 5v regulator was supplying 5v to the receiver module, and the receiver module was receiving, and generating a data stream. It's a multi-layer pcb, so I lost the signal track at that point, and lacking a circuit diagram, I checked on the possibility of paying for a repair - whilst awaiting a reply, I looked around FB Market, and managed to spot a much better control unit, complete with remote, for less than the cost of paying for a repair, and within collection range, so I bought it.

Older design just powers the motors on of with relays. The newer version uses more gentle, soft start/stop. I was never happy with the strain caused by my earlier versions sudden start and stop. I have yet to test this control out, but the seller was convincing.

Thing is, without the mover we are rather stuck for getting it out of my drive, onto the road, and coupled up - there is a 1 in 7 slope down, which makes it impossible to push, without lots of help. I keep a hand cranked winch, to pull it up in emergencies. The mover makes it so easy.