Blowing 10 amp blade fuse on Transformer/Rectifier EBL 99

[Make watts not war]

Good afternoon forum. We have a 2018 22km Burstner Lyseo Harmony on a Fiat Ducato chassis.

About 4 months ago, the red 10 amp blade fuse in the transformer/rectifier EBL99 responsible for the Truma heating control panel blew and has continued to blow when replacing the fuse.
Sometimes, the Truma control panel works for a number of hours before blowing, in that time the boiler and heating function well.
Sometimes the replaced fuse blows immediately when switching on the transformer rectifier.

All other services and fuses in the transformer/rectifier are unaffected. Lighting/bed/water pump etc are all good.

It has been a difficult task to find a motor home electrician in the North London/Herts area who seems willing to have a look at this problem, and I am loathe to take it back to the Burstner dealer.

Does anyone have an idea what could be causing this?

Many thanks if you can help

Phil

 

[Lenny HB]

As the Truma sometimes works and other times the fuse blows immediately I would start by carefully following the wiring loom from the EBL to the Truma checking very carefully the loom has not rubbed thrue and a wire shorting to any metal that is connected to chassis.

Another thing you could try is disconnect the 12v supply at the Truma and connect the Truma direct to the battery with a 10 amp fuse in line, if that blows its a fault with the heater.

 

[Make watts not war]

Thank you Lenny, both suggestions make sense. I would be more confident in carrying out the first investigation. Your help makes the situation more comprehensible. Thanks again, Phil

 

[jockaneezer]

Is your Truma heater dual fuel gas and electric ?

 

[autorouter]

Another possibility, depending on where it was stored, could mice have had a chew at the wires?

The 12V supply from the EBL99 is only for the heater control board, it doesn't supply any power to any heating elements. It goes from the 6-way connector on the front panel, Pin1 (pos), Pin5 (neg).

You could see if the wires are the same colour at the EBL end as at the heater end. Then pull out the 6-way EBL connector, disconnect at the heater end, and check for a short circuit. I appreciate it's an intermittent fault, so is difficult to reproduce, but you just might strike lucky. Or it might be a control board fault.

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[Make watts not war]

Is your Truma heater dual fuel gas and electric ?

Yes Jockaneezer

 

[Make watts not war]

Another possibility, depending on where it was stored, could mice have had a chew at the wires?

The 12V supply from the EBL99 is only for the heater control board, it doesn't supply any power to any heating elements. It goes from the 6-way connector on the front panel, Pin1 (pos), Pin5 (neg).

You could see if the wires are the same colour at the EBL end as at the heater end. Then pull out the 6-way EBL connector, disconnect at the heater end, and check for a short circuit. I appreciate it's an intermittent fault, so is difficult to reproduce, but you just might strike lucky. Or it might be a control board fault.

Hello autorouter, mice could be a possibility. I will explore the control board/ truma control panel connection. Thanks for your help, Phil

 

[Make watts not war]

Good afternoon all, thank you for your replies/suggestions.
I removed Truma control panel and adjacent electric control panel, checked and tidied wiring (didn't look bad), replaced 10 amp fuse and put the heating/hot water boost on for 20 minutes. Both functioned well. Switched everything off and on multiple times and the fuse did not blow.
Time will tell, once again, thank you for your help

Best wishes Phil