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wiring harness completely burned up


evanmc
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1985 110 2.5NA

Most unfortunate -- when I started my vehicle yesterday, the passenger compartment filled with smoke, and when I could get to the engine bay, I found the engine harness on fire.

Aside from the fact that this is a not-so-subtle reminder that I should keep a fire extinguisher on board, my question here is possible causes.

But first, some background.  This harness is only a year old -- I purchased one from autosparks in 2018 to replace my last one that caught on fire (yes, this has happened before).

In that instance, my alternator had fouled to the point that was the source of the problem (I believe), so I had that one rebuilt, replaced the wiring harness, and all was well for a year.

Seems like there are two possibilities for this last burning: the harness shorted out against the block (a crack in the insulation?  I certainly can't tell anything now that it has burned up) or the alternator is fouled again. Is my thinking wrong here?

Is there a way for me to test the alternator to see if it is OK, or do I need to remove it and take it to my local alternator shop?

 

I purchased this harness -- I did have to replace the loops on the alternator end with female connectors to fit my alternator, but I assume that was the correct one otherwise.

https://www.autosparks.co.uk/lr423-land-rover-defender-90-110-engine-wiring-harness.html

-Evan-

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Good suggestion -- i can certainly put some fuses in (where along the harness?)

And here's where I have a somewhat dumb question -- if I want to get things running again fairly quickly, can I just run some (reasonably large) wires between the starter and alternator?

The remaining wires on the harness look undamaged (I believe the harness also has wires to the starter and fuel solenoids?)

I'll replace the whole thing, but the timing here is bad in that I need to get it registered before the end of the month.

-Evan-

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Did this happen when you held the glow plugs on? It is easy to not spot a possible short to the engine on the glow plug feed wire. When you tightened the terminal screws on the glow plugs one of the terminals could have rotated slightly to make contact with the head. 

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14 hours ago, evanmc said:

Good suggestion -- i can certainly put some fuses in (where along the harness?)

And here's where I have a somewhat dumb question -- if I want to get things running again fairly quickly, can I just run some (reasonably large) wires between the starter and alternator?

The remaining wires on the harness look undamaged (I believe the harness also has wires to the starter and fuel solenoids?)

I'll replace the whole thing, but the timing here is bad in that I need to get it registered before the end of the month.

-Evan-

I can't recall the exact routing but between the starter and the two or three large brown wires which go into the dash (and power everything from there) is a good spot for a moderately sized midi fuse - I used 2x 20A blades (one per brown wire) on the ambulance because I had the space in an extra fusebox;

IMG_2981.JPG

 

If the only burnt wire is the alternator one then just replacing it with one that's at least as big as the old one (bigger won't hurt) should get you going - just be aware you need the warning lamp wire (brown/yellow) to excite the alternator so if that's damaged you need to replace that too.

 

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I thought the alternator output went direct to the starter solenoid, and the main vehicle live feeds came from the same solenoid terminal ? Long time since I have seen one though.

I would be inclined to take the vehicle live feeds direct from the battery and put some fuses in.

A thought though, do you have a rodent problem ? 

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Yes, the power feed from the alternator goes to the starter solenoid, and the main feeds for the vehicle are on the same terminal.

I just took a look at the chard remains.

It looks as if I did route two large wires from my alternator to the starter instead of using the wires in the harness. It was one of these wires that caught on fire, burning all the way from alternator to starter.  In the fire, the glow plug wire insulation was burned off at one of the cylinders. so that looks like it was collateral damage, not the cause.

The only alternator wire in the harness I am using is the one leading to the third terminal on the alternator (I am assuming that is for the warning light)

I did find that around the starter there was substantial amounts of oil covering everything -- including the starter solenoid. 

 

Yes, we do have rats, but I haven't seen any evidence of them.  Certainly a possibility

 

-Evan-

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2 hours ago, Maverik said:

Also be mindful of the dash lighting too... that is un-fused... ask me how I know this.

Yep, the whole Series lighting circuit is un-fused... because glass fuses start to smoke at around 15A. You can whack a blade fuse in there somewhere and it will at least keep the overall lot from catching on fire if there's a short, although it's not as nice as putting properly rated fuses in each circuit.

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21 minutes ago, Waldorf said:

I like the idea of using garden hose for that!

Old coolant or hydraulic hose can be tough as hell for protecting wires where they run near sharp things or risk rubbing... but it's a bit cumbersome for the majority of the loom.

I'd be concerned about the fact all the fuses are 20A, suggests there may be some slightly under-protected circuits there.

Still better than 99% of wiring done by LR owners though, neat and tidy and fused!

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11 hours ago, Maverik said:

Also be mindful of the dash lighting too... that is un-fused... ask me how I know this.

Mav

And the great ting about said dash light is, that it actually origins from the UNPROTECTED side of the fusebox, for some great reason... ask me how I know aswell...

/Mads 

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