johna
New member
A friend has a Hymer (German) motor home with a central electrical control unit that acts as battery charger as well as a 12-volt distribution board. Recently the 1.6amp fuse located inside the unit on the 230v side of the transformer blew when he connected to a site supply. We took the unit apart and after some basic tests replaced the fuse. It blew again, not immediately but after a short time. Inspection of the two 12-volt domestic batteries located under the bolted down driver and passenger seats, indicated a need for extensive topping up, 2 litres per battery!!!
Basic continuity tests of the transformer wiring do not show anything shorting out but a live bench test, no 12-volt connections, blew the fuse again. Use of 5-amp fuse wire with all wires disconnected from the low voltage side of the transformer resulted in successful operation with 12 and 25 AC outputs from the transformer. A re-test with the low voltage transformer connections re-made was also successful. Replacing the 5-amp wire with a 1.5 amp fuse is also working but only time will tell if this is permanent or not. It is now re-installed in the vehicle awaiting new batteries.
As the fuse has blown on the bench I have discounted the poorly maintained batteries as the direct cause but might they have contributed to some failure in the circuitry of the transformer output rectifier? Can anyone help on reasons why the 230-volt side should fail?
Basic continuity tests of the transformer wiring do not show anything shorting out but a live bench test, no 12-volt connections, blew the fuse again. Use of 5-amp fuse wire with all wires disconnected from the low voltage side of the transformer resulted in successful operation with 12 and 25 AC outputs from the transformer. A re-test with the low voltage transformer connections re-made was also successful. Replacing the 5-amp wire with a 1.5 amp fuse is also working but only time will tell if this is permanent or not. It is now re-installed in the vehicle awaiting new batteries.
As the fuse has blown on the bench I have discounted the poorly maintained batteries as the direct cause but might they have contributed to some failure in the circuitry of the transformer output rectifier? Can anyone help on reasons why the 230-volt side should fail?