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A curious electrical problem.
http://forum.triumphdolomite.co.uk/viewtopic.php?f=6&t=34574
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Author:  MIG Wielder [ Sun Dec 09, 2018 3:46 pm ]
Post subject:  A curious electrical problem.

I've been blowing fuses recently. Specifically the fuse protecting the unswitched, always live, feed from the fuse box. Normally this would disable all the items that are fed from the lower 35A fuse, but some time ago I fitted the 4-fuse MGB unit and split the wiring so only half my IGN OFF electrics disappeared.
Namely the clock, the hazards, and the ciggy lighter socket. And it seemed to be completely random. So as an aid to diagnosis I swapped the 30A fuse for a series of 10A units. I did note that plugging in an accessory to the socket would kill the fuse, but so did going over a bump. Luckilly each time it happened the clock would stop to I had a sort of time stamp of events. So it looked like the problem was in the area of the dashboard. I had the heater vent off and all the wiring at the back looked good. The loom looked good so I tracked it back to the rear of the clock.
To do this you have to take the glove box out ( 2 screws on the hinge plate, 2 screws at the lower edge of the box and 2 screws holding the chrome catch on. Ah-Ha ! the bracket at the back of the clock was loose !

Now if this bracket is not fitted in the "10 past 8 " position with the riveted-on spike going through the rear bracket it can move round and short the live 12V supply. I did note that the clock was a replacement as it was date-coded 1982 !
So a fault that has taken around 30 years to show itself.

Sorry there are no photos, it was getting late when I finished.

Author:  TrustNo1 [ Tue Dec 11, 2018 11:48 pm ]
Post subject:  Re: A curious electrical problem.

I did notice similar when putting a dash back together but thought is was just a dodgy connection on the one I had.

Author:  tony g [ Thu Dec 13, 2018 7:06 am ]
Post subject:  Re: A curious electrical problem.

Good find Tony :thumbsup:

Tony

Author:  MIG Wielder [ Thu Feb 07, 2019 5:05 pm ]
Post subject:  Re: A curious electrical problem. A follow up.....

.... There I was happily cruising along yesterday and I realised the clock had stopped again ! And yes. That fuse had blown again. :shock:
Now luckily this time the short circuit stayed on the output side of the fuse so I was able to determine it was on the Purple wire. But it disappeared again when I moved the loom under the glovebox and wouldn't come back. So it was out with the glove box again and a visual check. I had a better inspection lamp this time and I was able to determine it wasn't the clock wiring or the ciggy lighter, but where the loom is clipped to the rear of the bulkhead I could see 3 purple wires tightly compressed by the metal fixing clip. So I had the clip out ( the screw was well rusted in ) and I could see that this bit of the loom had been really compressed over the years just where the 3 purple wires leave the loom to join at the inline connector. But I couldn't see any sign of burning or bare copper. So for now I've separated out the purple wires, I shall get a plastic P-clip this weekend and separately tape up the purple wires, then the black wires and then the rest of the cables. I'm having to assume for now that I've had 2 separate faults. :shock:
I'm going to leave the 5A fuse in for now until I've got a bit more confidence. I'd be interested to hear if anybody else has this metal wiring clip just above the nearside parcel shelf. This may be a special SWK "thing" as it was the BL development car with and had extra boxes of electronics and wiring.
I have some photos this time.
Tony.

Attachments:
wiring clip1.JPG
wiring clip1.JPG [ 89.46 KiB | Viewed 145 times ]
wiring untaped2.JPG
wiring untaped2.JPG [ 93.12 KiB | Viewed 145 times ]

Author:  GTS290N [ Thu Feb 07, 2019 9:35 pm ]
Post subject:  Re: A curious electrical problem.

Hi Tony,

My September 1975 1850 cross-over model between Dolomite and 1850HL has (had) exactly the same clip but on the offside bulkhead, and the reason I know is the sidelights went awol with a smell of burning one evening. I actually traced it to aaarrggh, I can't remember exactly, a screw at the rear of the parcel shelf or similar cutting through the wires and shorting out, my fault. I can dig out the original post and photo's from the forum if required. But to repair the damaged wires involved pulling the metal clip from the bulkhead, and that wasn't easy! There's now a Nylon P-clip there!

Author:  MIG Wielder [ Thu Feb 07, 2019 9:57 pm ]
Post subject:  Re: A curious electrical problem.

Quote:
Hi Tony,

My September 1975 1850 cross-over model between Dolomite and 1850HL has (had) exactly the same clip but on the offside bulkhead, and the reason I know is the sidelights went awol with a smell of burning one evening. I actually traced it to aaarrggh, I can't remember exactly, a screw at the rear of the parcel shelf or similar cutting through the wires and shorting out, my fault. I can dig out the original post and photo's from the forum if required. But to repair the damaged wires involved pulling the metal clip from the bulkhead, and that wasn't easy! There's now a Nylon P-clip there!
Hi Bill, Thanks for that info; I detect these metal clips are quite bad news -40 years on ! I think I shall have a poke around on the offside as well next week. The problem is I don't think the sidelight circuit is fused; so this is why one may end up with burned wires.
Yes, Good Plan ! I think nylon P-clips are the way to go.

Cheers for now,
Tony.

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