7 replies to this topic

[MR J]

Thought I'd let everyone know not to buy cheap packs of blade type fuses.

My righthand sidelights and instrument lights had stopped working so I checked the fuse under the front scuttle and found it to be blown, I have had trouble with this inline fuse holder in the past and decided to replace the whole fuse holder with a blade type fuse holder.

The glass fuse that had blown was a 25amp (not sure if that is the correct rating for the sidelghts??) so to play it safe I replaced it with a 15amp blade fuse.

Turned the lights on and had a walk around the car to check if they were working, the sidelights where on but seemed really dim. After about ten seconds or so there was smoke pouring out from behind the dashboard, I quickly turned the lights off and rapidly disconnected the battery and ran for a fire extinguisher. Upon my return with the extinguisher the smoke had stopped and disaster had been averted.

I removed my walnut dash fearing the worst, that I'd require a new wiring loom, but was relieved to find it was only one wire that had melted, this was the instrument light live wire to my clock/oil pressure gauge/ voltmeter.

It also melted the internals and plug on the lightswitch, wondering why it had not blown the fuse I had just replaced I discovered that the fuse had got that hot it had melted the plastic on the fuse but not blown it!!

5 hours of repairs later, everything is back together. I have fitted a quality 10amp fuse to the circuit and all seems ok.

Moral of the story - Don't buy cheap packs of fuses!! The fuse I used came from a multipack of assorted fuses from poundland. Obviously cheap far eastern fuses which I very much doubt have been properly tested!!

[Ethel]

Lucas (glass) fuses and blade fuses are rated differently. The 25amp fuse would have blown at 25 amps, the replacement 15amp fuse was designed to carry 15amps continuously. The safety factor is roughly double so you had a circuit designed for 12.5amps protected by a fuse that needed about 30 amps to blow.

Pleased it wasn't a more costly lesson

[MR J]

Thanks Ethel, I understand that the fault was mainly my own by not tracing the fault first and fitting a correct fuse but surely the 15amp fuse should still have blown though if it got hot enough to melt the plastic encasing it?

[1984mini25]

the 15amp blade fuse still wouldn't have blown though, as the standard wiring wouldn't be able to handle enough current for it to.

Thing is, fues are designed to blow hopefully before the wiring fails, melts of catches light. So if a fuse does go investigate the problem before just sticking a higher rated one in and hoping for the best.

[mk1leg]

a good lesson learned............

[Dan]

This is exactly why I tell people all the time not to replace the fuses with blades unless they know exactly what they are doing. The 15 amp blade fuse, as said above would not instantly blow until the current reached 30 amps. Between 15 and 30 amps it will be in a slow-blow mode which can result in a lot of additional local heating, as well as the fault current heat. The circuit could be faulting at say 27 amps for hours on a blade fuse, but that would blow the glass cartridge and so the wiring isn't designed to be up to it. You fitted an incorrectly rated fuse, you nearly lost the car. The only real way to replace the fuses with blades is to redesign the wiring from scratch, like Rover did when they made the change. The balance of loads on the circuits and the size of the wiring isn't designed for the characteristics of blade fuses. Fortunately you had the presence of mind to switch off and deal with the problem, but if this had happened whilst you had left the lights on overnight for example the car would now in all liklihood be a write off. Glad it wasn't disasterous but I doubt the quality of the fuse was the issue.

[A362 TTU]

Just out of interest,

I have added a blade fuse box for the interior of my car - with one ignition live leading to it, to power up to 6 outlets. I added it for ease of adding anything to the interior.

What blade rating should I use for my car stereos live from it? It has a 10amp in....

[Ethel]

3 amps is typical and should be safe with any wiring you'll find on a Mini. Assuming it's a bog standard stereo & not something with enough base 'n volume to rearrange your internal organs. I'd be surprised if it doesn't say somewhere on the casing.