Blowing 10 amp blade fuse on Transformer/Rectifier EBL 99 (1 Viewer)

Make watts not war

Free Member
Oct 16, 2022
5
3
Funster No
91,926
MH
Burstner Lyseo 599
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

LIFE MEMBER
Oct 18, 2007
54,030
152,356
On the coast in West Sussex
Funster No
658
MH
Hymer B678 DL
Exp
Since 2008 & many years tugging
:welco:
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.
 
OP
OP
Make watts not war

Make watts not war

Free Member
Oct 16, 2022
5
3
Funster No
91,926
MH
Burstner Lyseo 599
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
 
Apr 27, 2016
6,931
8,095
Manchester
Funster No
42,762
MH
A class Hymer
Exp
Since the 80s
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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Last edited:
OP
OP
Make watts not war

Make watts not war

Free Member
Oct 16, 2022
5
3
Funster No
91,926
MH
Burstner Lyseo 599
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
 
OP
OP
Make watts not war

Make watts not war

Free Member
Oct 16, 2022
5
3
Funster No
91,926
MH
Burstner Lyseo 599
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
 

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