TONY BROOKS

‘Any wiring faults other than a bro­ken con­duc­tor need cur­rent to flow to give an in­di­ca­tion’

Canal Boat - - Technical -

Tech­ni­cal Con­sul­tant WE HAD A ques­tion on our Ask The Ex­perts fo­rum about an in­ter­mit­tent horn in which the reader said they had 12 volts at the horn but did not make clear if this was with the horn con­nected and sound­ing or just at the end of the ca­bles.

The im­por­tant thing to re­mem­ber when us­ing a volt­meter for test pur­poses is that in all but charg­ing or bat­tery volt­age checks, any read­ing will be use­less for di­ag­no­sis un­less what­ever the cir­cuit feeds is work­ing or try­ing to work.

This is be­cause any wiring faults other than a bro­ken con­duc­tor need cur­rent to flow be­fore they give an in­di­ca­tion by volt­age. This is es­pe­cially true with long ca­ble runs such as a typ­i­cal horn cir­cuit. Re­mem­ber that cir­cuit fault find­ing us­ing a volt­meter needs cur­rent flow­ing in the cir­cuit be­fore you will find any in­di­ca­tion of a fault.

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