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30A main fuse keeps blowing up on my 2001 thunderbird

5K views 8 replies 5 participants last post by  WSC 
#1 ·
The first time luckily, I was just a block from home when bike went to a dead quiet, with lights and ignition dead. The next morning, I inspected the fuse box and realised the 30Amp main fuse was dead. After replacing it with the spare, I got 4 miles on it before it blew up again, just as I was on the on ramp to the freeway.

i pushed it back to my friend's house and let it sit there for another couple of days, and got a new pack of fuses. after putting in a brand new 30A fuse, the bike started like magic, took me as far as a mile before it died again.

As i had a few more fuses to play with, i tried to put in another 30A fuses, with the key turned off. The fuse blew right away, and another one right after that.

interestingly, none of the other fuses had any of these problems.

What do you guys reckon- it is a problem with the battery or the regulator?
If it is the regulator, where can i get it from.
Any help is appreciated.

Thanks
Jai
 
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#2 ·
These bikes have a car type alternator where the regulator controls rotor field current & are much more reliable than the 'dump' regulators found on most modern bikes. If they do fail, it rarely causes a fuse to go.

More likely there's broken or chafed wire shorting to ground somewhere. Have a close look where the loom passes the headstock & inside the headlight shell. There's a wiring diagram posted on here if you need one.
 
#3 ·
Just FYI

I recently had a similar issue with my 2005 Rocket 3. Turns out the main 30 amp fuse was shorting out in the fuse block. When the wires were run by passing the block and a separate in line fuse holder added the issue was fixed. Been about 1000 miles since the fix and no more problems. Drove me nuts trying to track what was happening because the bike would die intermittently.
 
#4 ·
Replace the fuse with a test light. As long as there is a short, the light will shine brightly. Unplug things (start with the voltage regulator) until the light goes out, or at least dims significantly. When it does, you have found the problem. Since none of the other fuses are blowing, it probably is the charging system, or a wire feeding the fuse box or ignition switch. If you have a wiring diagram, see what is after the main fuse but before the other fuses.
 
#5 ·
Or just unplug the alternator connector (two pins, thick White & Brown on loom side) if you want to eliminate the regulator from things. But it's a low probability imo.
 
#7 ·
finally, i got to test the electricals on the bike.
thanks to WSC, i got a test light, and one thing I did realise is that the test light when connected across the 30A main fuse would keep glowing even when the ignition (key) was tuned off, but when i unplugged the battery from the circuit, this would stop, and the test light would glow when when the key was turned on
(I connected the black and red battery main wires without the battery).


would this mean, the battery is ****ed up and blowing up the fuses- also the level of the fluid in a couple of teh cells is almost at midline mark.

what do you guys think?

Jai
 
#8 ·
Not the battery. Although keep it filled properly.

This is a short. Guessing it occurs somewhere between the 30 amp fuse and the ignition. Battery can't reach out and fry a fuse if it isn't attached somehow. Now after you sort it out and the bike turns over but doesn't start? That would be the battery that has been thrashed through this whole process.

Also watch out for aftermarket stuff that was attached to the 30amp (was an alarm ever on this bike? heater? phone charger? GPS? Battery tender) If the cable was left dangling and unattached it could be the culprit.
 
#9 ·
Are you using a test light that is self powered? That's a continuity tester. You want one that's powered by the bike's battery. When you put it across the fuse it lights in proportion to how easy it is for the current to get to ground. With the key off (and no alarm, i.e. nothing powered with the key off,) the light should be out. If it's bright, you have a short.
 
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