12 volt running - am I missing the obvious?
We have recently bought our first motorhome - a lovely condition, one previous owner 2001 Autotrail Mohican on a Mercedes 316 base with only a few miles on the clock. We have had a full habitation service and a new leisure battery fitted.
Is someone able to offer any advice with regards to using the 12 volt system? To date, we have only used the lights, etc., using an electric hook-up to the house as we haven't managed to get away yet and it's off for its MOT in the morning. Today, however, I disconnected the 240 volt supply and assumed that the van would automatically switch to 12 volts running. However, nothing shows up on the control panel, no lights work etc.
Is there something blindingly obvious that I am missing in terms of switching from 240 volts to 12 volt operations? I have read and re-read the manual. I have also re-connected the mains and the control panel works fine. The battery voltage registers, the pump works, etc., with the 240 volts connected. I have 'rebooted' the control panel in accordance with the manual when connected to the mains but still nothing showing on the 12 volt front on the control panel and none of the 12 volt lights working etc.
Thank you
Comments
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I'm not familiar with your m/h but my first thoughts would be that the output of the 240 to 12 volt transformer unit may well be switched off ! If the l/battery was renewed a sensible engineer may well have turned it
off for his own safety !0 -
On my privious van there was a switch to switch on the 12V, is there such a switch?
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Thank you both for such speedy replies. ABM, - this could well be feasible so perhaps a trip back to the service agents. Cornersteady, - thank you also. I have looked high and low for a switch for the 12V but the manual makes no mention of where this may
be located.0 -
I assume there is a leisure battery fitted, as although normally required, I don't think one is always needed for 12 volt appliances such as lights and pumps to work whilst on EHU, as the charger would power them. It would also register a voltage. If a battery is present I would have thought this would register once the EHU was turned off.
Sorry disregard, just noticed the bit about new battery.
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the electric system may have its own manual? you could try googling the name of the transformer? Our 12V master switch is located next to where the transformer, breakers, fuses are.
One more thing, are the lights 12V lights, or do they look like 240 household lights?
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My caravan has a control panel and when I unplug the cable I have to restart the control panel to get the 12v system working. I would call the service agent they may be able to tell you over the phone! I sorted a few queries that way - much easier too!
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Cornersteady, there is a switch on top of the leisure battery casing and this is switched to the on position. Also, we have both 12 volt and 240 volt lights.
Thank you Pippah - I think, especially since I seem to be quite clueless on the operations, a call to the service agent is necessary in the morning.
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thanks for your replies (that doesn't always happen). Sorry I can't be of more help, a call should resolve matters, keep us informed.
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The slight puzzle is why you lights work on 230v but as soon as the mains is off the don't work. When connected to the mains the 12v side is usually run via a transformer. However this usually requires a switch to be on somewhere. Are you sure you have a
charge going into the battery? Is it possible you have a duff charger? One possible way of testing is the disconnect the mains and run the engine to see it that powers up the lights. You say that you can see the battery voltage when connected to the mains
but I assume you can't see that with the mains disconnected? Hopefully there is a simple answer?David
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The slight puzzle is why you lights work on 230v but as soon as the mains is off the don't work. When connected to the mains the 12v side is usually run via a transformer. However this usually requires a switch to be on somewhere. Are you sure you have a charge going into the battery? Is it possible you have a duff charger? One possible way of testing is the disconnect the mains and run the engine to see it that powers up the lights. You say that you can see the battery voltage when connected to the mains but I assume you can't see that with the mains disconnected? Hopefully there is a simple answer?
David
Mine is a caravan ...... not a motorhome. Even if the car/off/caravan switch is in the 'off' position I get all my 12 volt systems working when on EHU and a reading of 12+ volts on the voltmeter. If I unplug the mains & leave the switch where it is, I don't get 12 volts anywhere or a reading on the voltmeter either.
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I once owned the very same model you refer to but am finding it difficult to help as it is not clear what the problem is. I take it everything works fine when on EHU but it is not clear what is working from 12volts. Running the engine won't help because on that model the 12volt lighting is automatically disabled when the engine is started. If I recall correctly there is no mains lighting in this van, it is all 12volt. Is it only the lighting which doesn't work with the water pump running ok or are both not working?
Is this the control panel?
peedee
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Thank you everyone, this is very kind. Peedee, The picture you have posted is exactly the same as our control panel. Every button lights up on this control panel and lights, water heater, etc., all work on EHU. When the EHU is disconnected, I assumed that
12 volt operation would be controlled by this control panel by pressing the '12 volt on/off' button. When EHU is disconnected, there is no power to this control panel - nothing lights up. We have been 'under the bench; this morning. There is a control box
where nothing appears to have tripped and the leisure battery housing is just beside this. There is a toggle button 1\0 switch on the top of the battery housing and it looks to me that when switched on, the button should be illuminated. It is not lit up.I really appreciate the time and effort people are putting into trying to help out.
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we have only had MH newer than this....from 2007.... but none of the three weve had used any sort of 12v switch.....
any switching over to the 12/240v services happens automatically.
if on ehu with lights and water pump running....pull out ehu....all continues as before, just powered from battery....
similarly, pull up, park, turn on lights or pump, ehu not needed nor any switch as (i thought) 12v via battery was the default...
now plug in ehu lead, no switches involved, systems carry on working (again, i thought) from 12v battery but now with ehu providing charge to the battery.
i did learn that some systems (possibly ours...) automatically use a transformer part of the charger to provide 12v when on ehu.
if this is the case, and 12v is only NOT working when relying on batteries....i suspect a major fuse blown near the battery....as 12v seems to be working via a transfomer when on ehu.
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BoleroBoy, thank you. This is entirely what I had suspected should be the method of operation. Over the months that we have had the van, I was convinced that at some point, we must have been operating on 12 volts only because we don't keep it on EHU all
the time. Just wondering whether I was having an impending senior moment and missing a crucial operation. I really must become more informed about the electrical operations. There are a row of fuses on the driver's side wall in an upper cupboard but I would
not begin to know where to look. In my defence, the handbook is quite thin on the technicalities and a search of autotrail for technical manuals for this model was fruitless.Much appreciated.
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When the EHU is disconnected, I assumed that 12 volt operation would be controlled by this control panel by pressing the '12 volt on/off' button.
If it is not working when you press the top left hand button (the '12 volt on/off' button) then you have a problem. It is more than likely a 12v fuse. Is there an inline fuse near the battery terminals, if so check it. One of the problems I had was a 12volt fuse used to blow if the leisure battery got very flat and the initial charge surge used to blow a 12volt fuse, but I am dammed if I can remember where it was. I would also check in the engine compartement for any in line fuses.
peedee
ps I think I still have an electronic copy of the manual. I'll check but if you email me using the address available >on this page< I'll get back to you.
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the fuse im referring to (shot in the dark) would be a 25a one in line and close to (a foot away) either the positive or negative battery cable.....you cant miss it.....
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Weird, I had the same problem when I went out to my Bailey yesterday.
Went to isolate my 240v hook up, and lost everything.
On EHU, everything worked fine, without, nothing, no 12volt to anything. Checked battery, all fine, mover worked, master 12v switch on. Multimeter showed no charge back to
the battery on EHU.I found the inline 25amp fuse, but it wasn't obvious. It was tucked away between the floor and the underneath of the battery box, together with a usefull connecting block on the incomer.
Checked it, and it was fine. Then was checking each individual fuse on the BCA manufactured PDU and found a 20amp fuse in the middle of the bank marked battery.
Low and behold, blown.Replaced and everything fine.
Thinking back to returning home from Easter break, I disconnected the electrics from the car, with the engine running, and remembered it did not disconnect clean, I heard the ATC chattering as it disconnected.
I bet that blew the fuse.Check "all" the fuses
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An update on the progress so far. This is the second update I have written as the original vanished into the ether – I can only assume that I wasn’t logged into the discussion board.
I phoned the service engineer who installed the new leisure battery during the habitation service. He suggested that either the battery was flat, over-charged or had blown a fuse. I couldn’t see any sign of a fuse nearby the battery and the housing unit
is screwed to the wall. Although the engineer suggested that I look inside the casing, I thought better of attacking this with a screw driver to poke around for a fuse so phoned the company who manufactured the battery (Amperor).Amperor were incredibly helpful and patient. Apparently, what I was looking at was a battery charger and the toggle on/off switch is for physically charging the battery. Amperor’s advice was only to charge the battery when it needed charging (not to let
it drop below 11.5 volts) with the optimum levels between 13.8 and 14.4. I had naively assumed that, when plugged into the EHU, the battery would stop charging when it was fully charged. This is apparently not the case and the charger switch should be toggled
to the off position once charged or the battery may ‘cook’. Lesson learned there.To discover whether I had in fact cooked the battery, we tested the charger. To do this, the advice was to 1) switch the toggle on the battery charger casing to ‘off’ 2) connect the power to the motorhome via the EHU 3) turn on some of the lights 4) after
a few minutes, toggle the battery charger switch to ‘on’ and if the lights get brighter, then the charger is functioning. My lights got brighter so that was a relief. Also, the reading on the programme display was 14 for my battery so it seems that it has
survived.I had stupidly thought that this toggle switch decided whether or not one got access to the 12 volt supply for lights, etc.
The fuse is now looking the most likely candidate but the motorhome has now gone off to the local garage for its MOT. The beauty of having a village garage is that the mechanic issued a wry smile at our wide-eyed
blank expressions when we mentioned the issue of a non-MOT related blown fuse in the cabin. The upshot is that the mechanic has promised to find and replace whatever is wrong and provide us with some spare fuses.If this solution does not work, I will no doubt be back pleading for help. In the meantime, thank you so much to everyone for their helpful advice.
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well done.....
two things....firstly, more modern vans have 'more' intelligent chargers which can be left on and revert to float charge settings just topping up as required.
secondly, the dreaded....'where did my post go'.....issue....
i see this was a longish post and, even though you may well have been logged in when you started the post...the system registers 'non action' and after a few mins...(10??) it will log you out.
of course, it doesnt tell you!!!
so, after a long post, prior to hitting the 'post reply' button, just highlight the whole post and hit 'copy' to the clipboard....
then, if your post doesnt register, you can paste it in again...
good luck....with both....
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Just an update on the outcome of the dilemma posted in this thread. The 12 volt service is restored - it was a blown fuse. The battery compartment in the Mohican of this age and mercedes base is under the floor in a secret compartment, to the left of the
entrance door and directly underneath the charging unit. The fuse holder on the battery is clearly visible and it's easy to locate and change a fuse.Thanks again for everyone's replies.
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