[Engine] Burnt Out Loom (continued)

[Soarer]

Hi All

This is a continuation from my Burnt Out Loom post a couple of weeks ago. It is a problem with a 57 plate Partner, 72K miles, well looked after. I have now been to the garage and taken a better picture of the burnt out section and its pretty bad to be honest. What confuses me is that on the Saturday evening it drove faultlessly, then on they Sunday morning it would start. If I disconnect the battery, then reconnect the battery, it fires up for a second then stops. The garage tried clearing all fault codes etc, but no go, they sent it to a Peugeot Dealership to get a new key made up and programmed, still no go. Initially you guys suggested a failed Crank Sensor, so i bought one and gave it to the garage, but COVID 19 stopped play for a while and the van sat at the Dealership, then they garage brought back round to their workshop about 4 weeks ago, then when they went to change the Crank Sensor 2 weeks ago they found the burnt out loom. 

Hopefully the picture will let you see just how bad the loom is, how the van ran so well one night, then had this 12 hours later i do not know. Its not just the one bit attached either, but all the damage is in what looks to be about an 18 inch / 450mm section of wiring loom just below the battery tray area.

With some advice that Zion offered on what the garage had said about the wiring being part of the Glow Plug cabling for the heater matrix area (warm up the heater matrix water on a cold day for quicker cabin heat) I had wondered if an ongoing observation I had made was part of the issue. The van temperature gauge never reaches 1/2 like my 12 Plate Berlingo van (both are 1.6 HDi), it sits at about 1/4, so is the thermostat opening fully up and not allowing the coolant to reach the correct temp, thus keeping it cooler than it should be, thus causing the Glow Plugs to stay on trying to heat the water up (just a thought), but after seeing how bad the loom is I thought I would ask if anyone else has seen anything like this with their vans  

Has anyone else had experience of looms burning out like this, is it common, etc.

[Sol]

That does look pretty bad, though I've seen personally, a single wire powering a stereo that wasn't fused, go rogue when a short to the metalwork happened and the whole wire glowed orange like a cooker ring and started burning through everything it touched like a hot knife. One bad short can cause havoc in the harness. Maybe one of your auxillary heating plugs went short circuit, and maybe the fuse was way too high a value, and the short circuit current was high enough to cause the wire to glow but not enough to blow the fuse, due to the cross sectional area of the wire.

I must admit this isn't something common I've come across in 10 years of having Berlingo vans but it's always possible.

[Soarer]

That does look pretty bad, though I've seen personally, a single wire powering a stereo  that wasn't fused, go rogue when a short to the metalwork happened and the whole wire glowed orange like a cooker ring and started burning through everything it touched like a hot knife. One bad short can cause havoc in the harness. Maybe one of your auxillary heating plugs went short circuit, and maybe the fuse was way too high a value, and the short circuit current was high enough to cause the wire to glow but not enough to blow the fuse, due to the cross sectional area of the wire.

I must admit this isn't something common I've come across in 10 years of having Berlingo vans but it's always possible.

Thank you for your reply Zion

I am an electronic technician to trade (have been for 34 years) and as you can probable tell I am a bit surprised by what I am seeing. I only put one picture on yesterday but there are 2 or 3 more showing more damage, its just very unusual.

The problem with vehicle electrics is that the fuse in question may protect more than one device, but it does mean that any one device could pull more current than it should without exceeding the current rating of the fuse, but even in saying this the insulation of the cables should not melt away like these have done, if a cable is rated at 10 Amps it should not melt away at 12 Amps for example, very frustrating. The other thing that is confusing me is that the van was running perfectly on the Saturday evening, not even the slightest hint that something was amiss other than the usual 1/3 temperature gauge. Sunday morning it would turn over but not start, disconnect and reconnect the battery and it would fire up for a second. Then COVID stops play. Then after being at 2 different garages (independent and a Dealership) the badly burnt out loom is found, it is so bad that I am surprised that it ran so well on the Sunday evening.

Oh well, looks like its time for a new loom and get them to give it a good look over.

Thanks again for replying to this and the previous posts, greatly appreciated

Kind Regards

Tom

[Sol]

No worries Tom, it is a bit of a shocker. Looks like it was very close to being a fire. The car battery can shove a good few amps into a sub ohm load, easily enough to heat a small CSA wire to glowing hot. Glow plugs for example....if one plug shorts dead, the wire becomes the glow plug if the fuse is simply sized to supply them all. Not great, sub circuit protection should still be rated per individual wire but often as you say, they seem to use a 40A fuse to supply a bunch of 1.5 wiring and bad things happen if one wire gets shorted. Luckily you only have a damaged harness. Could have been a whole lot worse.

[Soarer]

No worries Tom, it is a bit of a shocker. Looks like it was very close to being a fire. The car battery can shove a good few amps into a sub ohm load, easily enough to heat a small CSA wire to glowing hot. Glow plugs for example....if one plug shorts dead, the wire becomes the glow plug if the fuse is simply  sized to supply them all. Not great, sub circuit protection should still be rated per individual wire but often as you say, they seem to use a 40A fuse to supply a bunch of 1.5 wiring and bad things happen if one wire gets shorted. Luckily you only have a damaged harness. Could have been a whole lot worse.

Hi Zion

Very true, as you say looking at the loom it couldn't of been far away from developing into a fire. At least I just need to buy a loom and then fir it.

Time for another post to see if anyone knows the part number for a loom or if anyone has one for sale.

Kind Regards

Tom

[Sol]

Might be worth finding an identical scrapper and follow it back to the nearest plugs or the fusebox itself. Some of those wires will go to the ECU, some to the fusebox and others to a plug maybe.