Mk1 and earlier coaches use re-wireable fuses which are numbered and polarised. The fuses are usually housed in a metal-clad box just below the sole bar and positioned close to the regulator housing.
It is not possible to fit the wrong type of fuse as a replacement for a blown one as the two
fixings are polarised with a small spigot which changes in position dependent on the value of the fuse.
Note that the spigot position (see below) is given as the "hour hand" position if the fuse is held
with its long axis vertically. 12:00 is straight up, 3:00 is 90 degrees to the right etc. referred to
the TOP tab fixing hole.
A table showing the (amperage) values of the various fuse
types and the correct size of tinned copper wire to use is shown below. Note that type 6 fuses are
usually stamped as "VI" to distinguish them from type 9 fuses.
Testing Fuses
Use either a resistance meter (the ultra-scientific way) or gently insert a matchstick in the sighting hole in the middle of the fuse (the quick and efficient way).
Type number stamped on both ends | Current (Blowing) Rating | Wire size SWG | Polarising spigot position (clock hour hand position) |
| 1 | 2.5 | 42 | 8:00 |
| 2 | 6 | 36 | 9:00 |
| 3 | 10 | 34 | 10:00 |
| 4 | 15 | 31 | 10:30 |
| 5 | 25 | 27 | 11:00 |
| 6 | 35 | 25 | 2:00 |
| 7 | 50 | 23 | 1:00 |
| 8 | 75 | 21 | 1:30 |
| 9 | 100 | 19 | 12:00 |
| 10 | 150 | 17 | 3:00 |
| 11 | 200 | 16 | 4:00 |
| 12 | 250 | 15 | 10:30 - lower tab is 7:30 |