Blown Fuse Warning

by alancuth Thu Aug 04, 2022 5:52 pm

I decided to remove the Thetford Oven and hob from my 2008 Nuevo to replace it with a Thetford Minigrill, having never used the oven or the pan storage. The 12 volt positive feed to the igniter circuit disappeared inside the back of the oven so I decided to cut it to make removal easier. The negative wire had a spade connector so this was simply disconnected. This caused an intermittent beeping noise and a message on the display "Fuse 7 Blown". Having put the Minigrill in place I connected the two wires to the igniter circuit connections and replaced the offending fuse.

Unfortunately the noise persists and the warning remains. The original 5amp fuse is OK when tested with my multimeter, as is the replacement. However, there is no power to the igniter circuit in the mini grill. Worse than that, there isn't any power to any of the igniter circuits (water heater or blown air heater). I tried removing the fuse and bridging the terminals with a wire with spade connectors at each end, but that didn't stop the warning or restore power. I disconnected the wires to the mini grill igniter and tried again without success.

I even resorted to disconnecting the 12 volt supply to the Bonus PS4U unit to see if this would reset things, but it didn't.

I can't think of anything else to try. Has anyone any ideas?

by Peter Brown Thu Aug 04, 2022 5:59 pm

alancuth wrote:I decided to remove the Thetford Oven and hob from my 2008 Nuevo to replace it with a Thetford Minigrill, having never used the oven or the pan storage. The 12 volt positive feed to the igniter circuit disappeared inside the back of the oven so I decided to cut it to make removal easier. The negative wire had a spade connector so this was simply disconnected. This caused an intermittent beeping noise and a message on the display "Fuse 7 Blown". Having put the Minigrill in place I connected the two wires to the igniter circuit connections and replaced the offending fuse.

Unfortunately the noise persists and the warning remains. The original 5amp fuse is OK when tested with my multimeter, as is the replacement. However, there is no power to the igniter circuit in the mini grill. Worse than that, there isn't any power to any of the igniter circuits (water heater or blown air heater). I tried removing the fuse and bridging the terminals with a wire with spade connectors at each end, but that didn't stop the warning or restore power. I disconnected the wires to the mini grill igniter and tried again without success.

I even resorted to disconnecting the 12 volt supply to the Bonus PS4U unit to see if this would reset things, but it didn't.

I can't think of anything else to try. Has anyone any ideas?

Yes - anyone who would replace a fuse with a piece of wire is intent on causing harm to himself, his property or to others - do not fiddle with electrical installtions when you don't understand them.

by alancuth Thu Aug 04, 2022 6:25 pm

I bridged the fuse holder just long enough to establish whether it restored current or cancelled the warning for a few seconds. I didn't replace the fuse with a wire permanently. Please credit me with some intelligence. Your comment was unnecessarily offensive.

by Tinwheeler Thu Aug 04, 2022 8:58 pm

alancuth wrote:I bridged the fuse holder just long enough to establish whether it restored current or cancelled the warning for a few seconds. I didn't replace the fuse with a wire permanently. Please credit me with some intelligence. Your comment was unnecessarily offensive.

You didn’t explain in your previous post that replacing the fuse with wire was very temporary. It would have been so much clearer if you’d said that. As it stands, I’m sure Peter and I aren’t the only people who gave an audible gasp of horror. Blown Fuse Warning 1f631

However, even as a temporary trial, I’m not convinced it was a wise move.

by Roopert Thu Aug 04, 2022 10:57 pm

Please don't take offence at Peter's comment - if you know what you're doing then you can mitigate the risks, but it would be dangerous to let it pass without comment, as it's not something that an inexperienced person should copy!

What make/model of control panel do you have? Your symptoms sound vaguely familiar, but I can't quite recall where I've heard it before.

by Peter Brown Fri Aug 05, 2022 11:03 am

I'm sorry you are upset but we all have a duty of care to those who read and trust in methods and techniques described on this forum, the majority of whom have very little knowledge of electricity and gas circuits.

It sounds as though you have an MES electrical system - there are various types. If you have the one I suspect then the 12v wire you are working on could be that for either the fridge or the step and they are not energised till the vehicle is in motion:

by alancuth Fri Aug 05, 2022 2:08 pm

The system I have is a Plug In Systems PDU-4M Fuseboard with Integrated Charger & ZF0251 Habitation Control Panel. The circuit I have a problem with is supplied by Fuse 7 which operates only the igniters for the heating and water heater (Truma Ultraheat) which do not, fortunately, only energise when the vehicle is in motion. The step and fridge are separate circuits.

by Jaime 007 Fri Aug 05, 2022 6:59 pm

Good evening,

We have never used our oven in the 12 years that we have owned the motorhome. However, the oven serves as a storage for our shoes!!

by Roopert Fri Aug 05, 2022 7:20 pm

My vague recollection of a similar problem is that it was caused by one of the legs of the fuse end contact breaking off, either just above or just below the PCB - but it's so long ago that I can't recall anything more about it.

If you're not already aware of them, it may be worth speaking to Apuljack Electronics, as they seem to specialise in control panels and fuse boards of the type you have.

by alancuth Fri Aug 05, 2022 8:15 pm

I’ve been in touch with Apuljack and await their response. Don’t fancy trying to remove the PDU-4M. It’s below the drawer under the wardrobe with very awkward access.

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