Fuse problem, advice needed

[Maxwedge]

I have a 1997 courier diesel, keeps blowing the brake light fuse rated at 15 amp. I did the sneaky and put a 20 amp fuse in- blew that too. a short term quick fix I stuck in a 30 amp. Whilst sitting at lights with brake on a light whisp of smoke starts coming from under the dash but the fuse did not blow.
Question is, obviously there is a short along the brake electrical sytem, does this indicate the problem lies under the dash? a short somewhere touching the body? or could it be maybe somewhere else. Just trying to establish whether where the smoke is is the problem area, or would its a possibility it can smoke under the dash and the problem (short) can still lie elsewhere.
Just trying to avoid ripping the interior apart and spent hours in the wrong area, thanks

[Boosted_162]

Putting a larger fuse in is a very bad idea. Its smoking because the wiring obviously is rated at less than 30amps, so the wiring is now the weak point in the system, not the fuse as was originally designed.

Could possibly have a faulty bulb which is causing it to short? Maybe try removing one bulb at a time to see if it still blows fuses (only a 15a one tho!)

[nz_climber]

Like was said above, the smoke is a new problem you created with the wrong fuse which will also have to be fixed.

If you are lucky the other fault will be next to the smoking wire, but could be anywhere in the system, you have to narrow it down by fitting 1 light at a time or isolating different parts of the system, a multimeter will be very helpful for this.

[matt dunn]

What you will find is where the wire in in a group of 5 or 6 it can dissapate the heat,
but in the dash where it is in a group of 60 it can't,
so it gets hot and melts the loom from the inside out,
not just the one wire but the whole loom.

So if the short is in the tail lights at th back it can melt the wire under the dash first.

Had a vehicle at work like that a while ago, a friend had tried to fix it for them and kept putting bigger fuses in,
by the time it got to us it needed a new loom and was over $1k of damage.

[AE82 FXGT]

As above, you never should really put bigger fuses in. Pull out all the brake bulbs put original size fuse in and see if it blows, if it does you know that its something else.

I suspect that the horn might run off that fuse too, so be sure to check that along with any trailer wiring, which I would suspect before looking into the vehicle loom (well before you cooked it).