Blown fuse and melted fuse box.

[TVR653X]

As I posted in my previous thread, found here http://www.pistonheads.com/gassing/topic.asp?h=0&a... I was going to tackle the fuse box as my interior fan wasn't working. Whilst my mate (who is an engineer) looked at the wiring diagrams, he realised that what I thought was a missing fuse, was infact a completely melted fuse, that had also melted part of the fuse box. Looking at the diagram, it was a 15 amp fuse for the full beam headlights. Luckily, the fuse box wasn't sufficiently damaged that it wouldn't accept a new fuse, so we put a 15 amp fuse in there, and the full beam started working again. We also examined the fuse for the interior fan, but this was intact. We left the lights on, and then tried switching the fan on. The lights dimmed (suggesting current was being drawn from the battery by the fan motor), but the fan still refused to turn on.

First question:
Is my fan jiggered, and if so how do I get to it to examine it?

Second Question, and more importantly:
Why has a fuse in my car seemingly melted to the point that all that was left was a bit of charred black metal?

[ketvrin]

test the fan by jury-rigging a supply and earth direct from the battery... if it spins then its not the fan but the circuit thats at fault...

if it doesnt then it probably kept blowing fuses and maybe someone stuck a big fuse in in a vain hope to cure the problem... it could have gotten very hot before it too blew

K

Edited by ketvrin on Friday 4th December 13:42

[TVR653X]

ketvrin said:

test the fan by jury-rigging a supply and earth direct from the battery... if it spins then its not the fan but the circuit thats at fault...

if it doesnt then it probably kept blowing fuses and maybe someone stuck a big fuse in in a vain hope to cure the problem... it could have gotten very hot before it too blew

K

Edited by ketvrin on Friday 4th December 13:42

Jury Rigging? How do I connect that up? I don't know how to get to the fan, that's my problem.

Also, the fuse that blew was not for the fan, it was for the headlights.

[ketvrin]

TVR653X said:

Jury Rigging? How do I connect that up? I don't know how to get to the fan, that's my problem.

Also, the fuse that blew was not for the fan, it was for the headlights.

Can you get to the back of the switch ? theres only the White/Green wire supply to the switch and two wires (yellow/blue, yellow/red = different speeds) from the switch with the earth off the fan itself. You should check that theres 12v getting to the switch first, if there is then connect that wire direct to each of the other wires in turn (effectively eliminating the switch as the culprit) if the fan still does not turn then its either the fan itself or the earth - but as you say, if you cant actually get to the fan its going to be tricky... dash out even...
If theres no supply to the switch, then run a live direct from the battery to the switch - that eliminates the circuit upstream of the switch itself. thats about as much as I can advise...

hope that helps

sorry - misread which fuse had burnt out

K

[TVR653X]

Ok cheers. I'll have a go.

[mep12345]

I have been told that to get to fan (I assume you mean the in car ventilation fan) you need to remove the dashboard - my ones bearings are noisy but have decided not to touch until it goes completely as by all accounts it is a bugger to do

Mark

[clarenceboddiger]

TVR653X said:

We left the lights on, and then tried switching the fan on. The lights dimmed (suggesting current was being drawn from the battery by the fan motor), but the fan still refused to turn on.

First question:
Is my fan jiggered, and if so how do I get to it to examine it?

To me that sounds like the Fan is receiving a supply but is mechanically unable to turn, maybe stuck due to lack of use or something jamming it. If it was burnt out I would have expected
1) The fuse to blow due to a short circuit or
2) The lights not to dim due to an open circuit and hence no current being drawn.

As for the melted fuse, it sounds like a bad connection on either the fuse blades or the wires to the fuse holder, this causes heating of the blades over a long period which gets hotter but isnt sufficient to blow melt the metal in the fuse. A short circuit gives a very high current for milliseconds which will melt the metal in the fuse, but happens so quickly that the plastic doesnt have time to melt before the fuse blows.
HTH

Edited by clarenceboddiger on Saturday 5th December 06:18