BIG -" Realy big"- Fuse Blown ????

[Keith Mayers]

Any advice on this would be great ..... My other cappo has been wrapped up in the garage for the last six months and I tried to start the engine-- but no go----flat battery. so I took the battery off the car and charged it up. So today I put the battery back on the car and connected the +ve and then as I connected the -ve I heard a "crack" and there was a spark as I connected the -ve lead. --thought i might have left something switched on six months ago causing the flat battery. Then swiched on ignition --nothing --tried lights -nothing -- tried radio--nothing --in fact all dead DEAD.. SO I found the 60 AMP main fuse blown==located where I heard the crack - just behind the nearside headlamp This fuse is held in by two set screws and ==to me == after looking at the wiring diagram - is the fused return "feed" from the alternator . So somewhere on the heavy white wire side of this 60 amp fuse is a dead short --WHERE ??? .. I have also withdrawn the other fuses in this fuse box but the "dead " short still exsists across the 60 amp one ... is it alternator ?? or does this heavy white wire do something else ???... In the meantime I,m going to unwrap the plastic "TUBE" thingy and find out where it,s going . ,,But when this fuse blows and every circuit is dead on the car is "where do you look ??? " HELP !!!

[Ian Linden]

The white wire from the alternator splits two ways - one way goes to the 60A fusible link (and thence to battery +), and the other goes through the harness to the ignition switch, becoming White/red tracer at some point on the wiring run. If the ignition is off, there should be no connection from that point to anything, but a fault in the switch is possible.

The possible locations for the fault to earth are therefore:

The fusible link holder - disconnect the white from it and see if the short on the white vanishes, using a test lamp and battery, or an ohmmeter. If not....
The alternator - disconnect the white from the alternator and see if the short vanishes. If not..
The Ignition switch - disconnect the harness connector leading to the switch and see if the short vanishes. If not...
The harness connectors on the white-white red line. There appears to be two - one in the engine compartment, and one near the ignition switch. The engine compartment one has a Black/blue wire which carries earth, so that is a possibility. If not...
The harness wiring on the white- white/red line - I would buy some suitably heavy wire, and rewire from the fusible link to the alternator and the ignition switch, bypassing the defect. Insulate the three bare ends of the discarded wiring run and you should be good to go, as they say

All the above assumes there is a single fault. If there are two faults which together provide the short, life can get more difficult, so let us hope that is not the case.

[Keith Mayers]

Just a little update-- Well,,- took the alternator out - and had it tested at the local specialist --all OK ,, drew 3 amps on test bench (ign warning light and supply to elec magnets) when run up put out the usual 14.7 volts. So removed the harness off the car unplugged oil press wire, starter solenoid, reverse light wires , earth and then stripped away all the wriggly plastic and insulation tape to expose the wires to look for a breakdown of insulation -- all insulation OK . BUT , NOW !!! I find the heavy white wire is "piggy backed" crimped and soldered at a point halfway along its run and the piggy backed wire returns and goes into one of the multi pin plugs at top of offside front suspension and at this plug it then connects to a heavy wire -white with red trace ... Top man IAN !! you said this could be the problem at the ignition switch --- so now I,m going to look at the wiring diagram for white with red trace .. that,s where I,m at ....Look forward to the next episode ..

[Keith Mayers]

Problem solved but it,s a mystery ?? The battery appears to have "reversed "its polarity YES !! I can,t believe it !! I,ve put another battery on the car and all OK. I bet nobody can give an explnation of this situation ???? I,ve tried to send IAN a PM but not sure If it has sent .. WONDERS WILL NEVER CEASE ..

[Ian Linden]

I did receive Keith's PM, and turned up a reference which sheds some light on the issue - http://answers.yahoo.com/question/index?qid=20090428060020AAtJkAg. It would seem that Keith's battery was heavily sulphated.

I now charge mine once a week, and use an isolator to prevent discharge.

[Adrian Furniss]

Having ruined one battery through lack of use, I keep one of these permanently plugged in and running.

It monitors the battery state and kicks in with some charge when needed.

There's a neat little connector under the bonnet which allows the unit to be disconnected when the car is in use.