Rewiring the heater

Practical Boat Owner - - Practical -


Part of the pre­vi­ous wiring in­stal­la­tion. Get­ting the wiring right is key to re­in­stalling any kit when multi-strand cable looms are in­volved. With older sys­tems the wiring may dif­fer from new colour codes, so make notes and take plenty of pic­tures.


With the bat­ter­ies off, the first thing to be dis­con­nected was the red pos­i­tive lead run­ning through the main 25A fuse into the bat­tery iso­la­tor switch.


The next job was to iso­late and dis­con­nect the neg­a­tive lead, and this was the brown cable on the neg­a­tive bat­tery ter­mi­nal. En­sure any other ca­bles af­fected are re­con­nected and se­cured.


After re­mov­ing the wiring cover, the glow plug cable is ex­posed. This bolts on to a small stud on the heater body. To pro­tect the con­tact head and ter­mi­nals, I then put a bit of tape around them.


Now the main ter­mi­nal block from the con­trol box could be re­moved, leav­ing all wires to the heater itself dis­con­nected.


Where twin wires were the same colour in the ex­ist­ing in­stal­la­tion, a piece of tape was used to iden­tify sep­a­rate wires. It was some time later be­fore I had to re­con­nect the ca­bles, so taped marks helped me iden­tify the right con­nec­tions.


The var­i­ous con­nec­tor blocks were dis­con­nected but had not suf­fered the cor­ro­sion af­fect­ing the other parts of the sys­tem due to the lib­eral use of a coat­ing of sil­i­cone grease.


The multi-core cable which would need to be length­ened was iso­lated from the rest of the wiring and cut.


All con­nec­tor blocks and ter­mi­nal con­tacts were la­belled and num­bered. The male spade ter­mi­nals were care­fully re­moved from the block with a pre­ci­sion screw­driver. New ones would need to be fit­ted to the length­ened multi-core cable.


A wa­ter­proof multi-ter­mi­nal box was fit­ted into the bilge for con­nect­ing the ex­tended wiring runs. On the right side are the old ca­bles in and, on the left, the new ca­bles out.


Iden­ti­fy­ing and find­ing the right­sized new spade con­nec­tors took a while, but in the end I found­po­ to be very help­ful and rea­son­ably priced.


The con­trol mod­ule was fit­ted to the new wooden pad pre­vi­ously epox­ied to the tran­som. (See ‘Fit­ting the mount­ing pads’). It was made large enough so there was a clear area for se­cur­ing cable runs with clips.

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