2007 Topaz habitaion electrics

We have just been away in our 2007 Topaz and I noticed yesterday that the lights were dim and became more dim if another light was turned on (or any other 12 v appliance). I was on electrical hook up.

If I switched to the habitation battery instead of the centre position on the control panel the lights were OK. It was as though there was a problem with the electrical hook up supplying a rectified 12 V.

On our way home this morning I could smell burning after a few minutes. We stopped immediately and the electrics were found to be smouldering under the bench seat (where the leisure battery and water heater are).

I managed to pull the offending wires out of the small hole used to release the water from the water heater, 
There were two red wired going to a smouldering bit of plastic (not much left of it). The wires had spade connectors going to the molten plastic.

I managed to pull one of the spades off and taped the ends of the wires and turned off all circuit breakers.

We managed to get home OK after that.

Does anyone have any idea what is causing the problem.

All I can think of is the molten plastic was some sort of fuse or a diode (as it han only two connectors) with a bad connection. A bad connection with high current can cause heat.

 
Thanks
Martin

Can't help with your burning but the centre position of your switch does nothing. You select veh or hab to direct charge to which battery you select when on hook up, so you were not putting any charge into either battery so that's why your battery was running down. When on hook up, 12v supply to lights etc is provided by the charger through the battery but not when in centre position.

Thanks for your reply. When we bought the van a few years ago we were told by the seller (Todds in Preston) that  the vehicle battery was not wired up in the control panel. It is even more confusing as to what is going on.  

I did not realise that the  rocker switch on the control panel had to be in the HAB position to charge the battery as I thought this just to select the battery to use. 
This is starting to make a little more sense now. As you said the reason for the lights starting to fail is that the leisure battery was running low.
The problem with the burning only happened when the engine was running (i.e. charging the battery).
If the 2 input device that was melting is just a connector connecting two wires together then if one of the wires was making a bad contact it would generate heat and probably not charge the battery. 
The 2 input device was not fixed to anything i.e. it was just hanging in mid air.
Note one end of the wires was in the region of the battery (probably the change over relay).

You could check to make sure there is no continuity between your live wires and the negative and body of the motorhome. Before trying to switch it back on and replace whatever has melted.

I have just been home to take some photographs of it. It looks like the burnt device is the 30A fuse going to the positive terminal of the battery.
Attached should be a photograph and the wiring diagram
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The top connector looks to be only just pushed on a little way , this would cause a high resistance and get very hot , I  also never buy cheap fuses of eBay or Amazon as there are a few dodgy Chinese nock offs about

The connector had been separated by myself so I could dive back home. I put them back to take the photograph. As you can see the spade did not come apart  and it took a lot of effort to break the wire off - the fuse was probably therefore intack.


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So its a 30A green coloured fuse that should be in the holder.
There has been a LOT of posts re this type of holder and its ramification
Check out 30 A fuse in the search box top right of this start page.  [You must be registered and logged in to see this link.]
frederic
a good  pic is worth a lot of words

more info 

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 by [You must be registered and logged in to see this link.] Tue May 03, 2022 4:37 pm

Habitation,  ( centre is off,  and vehicle position puts charger to vehicle battery)  and charger switched. on.  only way to check is with a voltmeter on battery terminals or using the panel meter
Do a search in search box 
frederic

Thanks Fredric. Do you know where I can get an Autobar fuse holder from?

I think I will look for the original  fuse tonight.

Hi
Any motor Accessory shop or Halfords should have them  or even from e bay
IMHO the small fuse holder is really only suitable for lower amperages 
Better to use the larger as it will have less resistance to the current flow and therefore should remain cooler.
I have electrolubed all the accessible spade and relay holders/multi connectors on the 12v habitation side in our Topaz especially on the Eber control cables as there is a large startup draw current in order to fire up and shut down the unit
frederic

Thanks. I have just got home and the interior lights, water pump etc still work running off the 240v input so nothing else looks damaged.

12 Volt Planet: Auto & Marine Electrical Components ...

Best place for anything 12v, that's what they do, used them a lot, no issues
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Will this fuse holder do. It says the  terminals are for 4mm-6mm wires?


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The only one at Halfords is an inline Maxi Blade fuse holder. I am assuming with this type of fuse holder (inline) you cut the loop of wire from the fuse holder in the centre and somehow connect the wires to the existing wires that went to the existing fuse holder?

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The one from 12v planet will need the proper crimping pliers to fit the the terminals correctly ( normal crimp pliers do not do theses terminals )  the Halfords one is as you say cut the loop and join the wires , with this it is either crimp connectors or a length of shrink tube placed on the cable first and then the wires soldered

I do have access to crimp tools but I was really wondering if the existing cables are too small in diameter for the crimps on the spade connectors - they do not look 4mm in diameter (core diameter that is)

I think the 4mm/6mm size would be ok as the actual end of the terminal when crimped grips the out insulation and the inner crimped connects to the bare wire, I had to buy the special crippling tool to do a job that I have just done on the EC500 that uses the same terminal ends

The three-way switch is confusing. the Hab and Vehicle positions determine which battery received charge from the 240V hookup. The middle position means neither battery is being charded.
However, the 12v interior lights etc. are all powered from the leisure (habitation) battery. If the switch is set in the centre or to the Vehicle setting the lights will eventually drain the hab. battery.
In effect, with the switch set to Hab, the lights etc. are drawing power from the Hab. battery, and the charger is topping it up again. 

Like you, while on hookup I've occasionally left the switch in the central position and wondered why our lights are starting to dim. Flicking the switch over to Hab. immediately sorts the issue and charges the battery.

I fitted the 4\6 mm fuse from 12voltplanet. I ended up crimping then soldering on the join of the crimp. It seemed to work OK. I ran the engine for 5 minutes with no sign of any rise in temperature on the fuse. I have ordered a new leisure battery which arrives tomorrow. Thanks for your help.

That is confusing, and completely different to ours. I'd thought vans of a similar age (2005-06) would have similar charging arrangements. Not so!

It does look like the vehicle battery is not used as the power source when the switch is in the vehicle position on my Topaz. I know this as I had no other power source when the fuse melted. When the switch was in the habitation position I could use the electric hook up as the power source.

That would make sense - otherwise you would risk draining the vehicle battery using hab. equipment with the result that you couldn't start the vehicle. That's why there are two batteries: you can run the hab. one down, but the starting battery remains charged.

On mine all the 3 position switch does is direct the charge voltage to either the Vehicle battery or the Habitation battery or neither. If there is no hook up power the charger won't run and the 3 position switch is irrelevant.