HELP! 12v system playing up

  • Thread starter Richard James Burfoot
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Richard James Burfoot

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So, we're just about to go away and the 12v system on our MH is playing up:

When just on 12v it's dead (won't switch on)
When plugged into 240v it only works after pressing the charge switch and trips off when using pump etc. When on it shows a fully charged battery (which is 3 months old).
When on 12v you can make it work by holding down the charge switch.

Really weird! Any wisdom you can offer would be gratefully received! Hopefully getting a slot at our local MH garage but with the Easter hols beckoning I'm not convinced I'll be lucky.

Thanks!
 
Sorry Richard, more specific details required. What do you mean by "charge Switch" ?. Do you mean NOTHING works on 12volt ? What happens if the engine is running ?.
 
It sounds like that battery is faulty and when you press the charge switch, you may be running the system off the charger. Most chargers can supply 5 amps or so and run small 12V accessories but they may not give enough to run a pump.

When you say it shows a fully charged battery is that on the control panel with LED lights or something? It is worth taking a multimeter and putting it directly across the leisure battery terminals, to see what the reading is.
 
We had a faulty battery once - watching the rugby World Cup Final (England v somebody!) and all power went. The only way we could keep watching it was with the engine running - not normally recommended but necessary for our enjoyment at the time.

It turned out that some of the plates were short circuiting in one of our 2 batteries and this took the lot down. New battery fitted (under warranty) cured the problem.

Hope you can sort it out soon.
 
Yes, sounds like a battery problem, or a faulty/loose main connection to the battery. I've also known there to be a build up of oxide between a battery terminal and the battery post, it all looks fine but checking with a meter will show 12v on the battery posts but nothing if you measure on the terminals.

AndyC
 
Another vote for battery problems, I had very similar and only after some head scratching I remembered
the leisure battery was still on my garage bench where it had spent the winter. Doh..
 
Thanks everyone so far for your helpful comments. So here goes with the detail:

1) The system won't switch on in the normal way when running on the 12v leisure battery ... unless you press the leisure battery charge switch, then it switches on, but as soon as you demand very much from it, it trips off.

2) Same as above when connected to 240v except it takes a bit more to trip it off. All 240v appliances work perfectly (water / fridge).

3) When it you switch the ignition on or run the engine everything works perfectly without fault.

If it's the battery it can be replaced immediately, although it's only 3 months old.

However, in the short term (2-3 days) until a problem can be sorted, will it hurt to run everything from the engine battery (ignition switched on but engine not running) whilst charging it from the 240v through the control panel?

Thanks so much everyone for your advice - I'm afraid I'm not good with the mechanical / electrical kind of stuff.

BTW, I'm in Poole, Dorset.

Cheers!

Richard
 
Now we have further details Richard, may I suggest you examine the earth (return) lead from the leisure battery at the point where it is fastened to your chassis,body or whatever it is fastened to. With the engine off & mains hook up disconnected, switch on a few domestic items (lights etc) then wiggle the earth lead around at its chassis/body connection point and see what happens.
 
ivecotrucker said:
Now we have further details Richard, may I suggest you examine the earth (return) lead from the leisure battery at the point where it is fastened to your chassis,body or whatever it is fastened to. With the engine off & mains hook up disconnected, switch on a few domestic items (lights etc) then wiggle the earth lead around at its chassis/body connection point and see what happens.
Click to expand...

Thanks for that Ivecotrucker - will try that tomorrow. Fingers crossed!
 
Another small detail:

It seems that when it's on the 12v leisure battery and you test the voltage, the lights and the meter / needle on the panel are pulsing, whereas when on the engine battery it's all good (as it should be and has been in the past).
 
Firefox said:
It sounds like that battery is faulty and when you press the charge switch, you may be running the system off the charger. Most chargers can supply 5 amps or so and run small 12V accessories but they may not give enough to run a pump.

When you say it shows a fully charged battery is that on the control panel with LED lights or something? It is worth taking a multimeter and putting it directly across the leisure battery terminals, to see what the reading is.
Click to expand...

I'd not thought of that Firefox; I wasn't aware it could do that. The fully charged battery shows on the control panel in the van. I've checked the battery itself and it was showing 12.25v which I guess would suggest it's healthy, although it was on hook-up at the time.
 
1. Check the leisure battery earth. A faulty earth can produce some weird results. Check and tighten Positive and earth terminal/post connections

2. Swap the engine battery into the leisure compartment as a test. If interior electrics now work you will know to replace the leisure battery. (Before doing that I would take the battery out and put a charger directly on the battery using croc clips. See if you can charge it overnight to give you 12.8+ volts after it has had time to rest)


(edit: 12.25 V is not too healthy it is only 50-60% charge. It should be showing 12.8 to 12.9V at full charge)
 
Last edited by a moderator:
Richard, do you mean the domestic lights pulse on & off when you depress the voltage test button, or do you mean an indicator light pulses on your domestic electrical control unit come voltage meter ?.
 
Sorry to bother you again Richard but I've only just read your reply to Firefox. If your battery is only showing 12.25v WHEN ON CHARGE that is rather strange because it should read at least the output voltage of your charger & that ought to be at least 13.8v. Are you relying on the onboard meter panel or using a proper mega or multimeter ?.
 
:rockroll:

Well thanks to Charles & Son in Poole I'm back on the road and all seems to be working as it should be. It was a problem with the earthing for the leisure battery which was shorting the whole system out. All fixed now and ready for a few days away after the busyness of Easter.

Thanks to you all for your advice and ideas!

Happy Easter to one and all!

Richard
:p
 
ivecotrucker said:
Sorry to bother you again Richard but I've only just read your reply to Firefox. If your battery is only showing 12.25v WHEN ON CHARGE that is rather strange because it should read at least the output voltage of your charger & that ought to be at least 13.8v. Are you relying on the onboard meter panel or using a proper mega or multimeter ?.
Click to expand...


We were using a multimeter - can't remember if it was on charge or not now, but will check it all out tomorrow afternoon. It is at least not all working, although I'm £116 lighter!
 
ivecotrucker said:
Richard, do you mean the domestic lights pulse on & off when you depress the voltage test button, or do you mean an indicator light pulses on your domestic electrical control unit come voltage meter ?.
Click to expand...


I meant the lights on the motorhome control panel.
 
Purchase a digital volt meter, something no motorhomer should be without

Firstly put it on the 20v DC scale some say 20- not 20~ which is AC as comes through the mains.

Measure straight across your leisure battery, there should be about 12volts ish.

I agree with checking your earth connections, if wiggling doesn't do anything, get a length of wire, get some one to hold a bare end on the Negative terminal (-) and touch the other end of the wire on an exposed piect of bare metal on the bodywork or even the negative of the battery. IE making sure that there is a good earth. If this fixes things then obviously there is an earthing problem.

Let us know after this test
 
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