Wards headlight modification

[Seaking]

Tanya
I do hope that the retailer gives you a good explanation and a refund

Cheers Glenn

[mike@thenook]

I'm interested Jonno, definitely.

cheers

[SaskStag]

Thankyou so much!!!!!! That all makes sense as what happened and fits my thoughts. Interestingly, the first thing I noticed after fuel pump stopped ticking, dash lights all good, was the starter sounded sluggish like a flat battery which can fit the slow trickle of charge beforehand. Then clicking sound and smoke - lots of it.
Can rule out manifold, alt fan, but will look for pinching/rubbing points; back of alternator is my prime suspect. Wire ran from back of alternator along back of the header tank to relays above expansion bottle; there is a rubber lined clamp for the brown and earth wire behind header tank, but wire is undamaged here.
This headlight brown wire has most damage so assume that was source; fried portion is closer to alt and point where there was a break is shown on photo by alt with last 5 cm or so still on alt. Grounded to alt body?
The club mechanic is also coming out tomorrow and told me not to touch anything - well - I did poke around a bit looking for a cause, but can easily recreate the scene of damage.
PDWA switch and header tank level switch wires, lights earth wire are all collateral damage.

In answer to StagJonno's question (thanks, would also like your fusing input!). LHD side feed was off the relocated alternator BATT position. RHD feed was straight from battery + and looks fine.

Will report back, ordering new wire and buying in-line fuses

[StagJonno]

Heading off for a long w/e in New York soon, and a bit busy after we get back, but will aim to start building up the fusing review at the end of next week.

Jonno

[Enigma66]

From what you write it sounds like the brown feed wire may well have grounded to the alternator body. When you initially ran the wire, was it fairly snug, or more slack across the back of the alternator on its way to its clamp/hold-down? After only ten miles it should not have chafed through already, that seems very fast. I ask about the brown wire's run thinking that when accelerating, the engine lifts up on the left side, and if the wire run wasn't slack enough to allow for the engine movement, it could have pulled across the back of the alternator (against the rubber lined clamp holding it), causing the wire to become tight against the alternator then to chafe and cut into the wire's insulation. 5 cm to the break sounds like about where it likely was grounded, about the back corner perhaps?

This incident may have ruined your alternator, too; it depends on how well its design protects its diodes. Once you're operational again, keep an eye on your battery charge and condition. Even if it all appears to be functioning properly at first, it may have what we in the electronics industry call infant mortality, so keep a close watch until you have confidence in it.

The type of fuse you use will determine the fuse value you require. If you use modern blade type fuses, they are rated for the regular load current flow. If you use glass fuses like the original panel uses, then you'll have fuses rated at the current where they blow after one or two seconds. There is about a two to one difference between the types. Fuses are supposed to be down-rated 10-20% when calculating what size to put into a circuit. This means that when you figure the amps for the circuit, calculate using 9 for the voltage instead of 12, so you don't have your fuses blow unnecessarily. A 13 amp draw is about what your calculations should indicate, after downrating, since you're running only two headlamps per brown feed wire.

From lethal headlights to almost lethal car incident (to the car, not you). They wanted to "get you" one way or the other, it seems!

Michael

[SaskStag]

Club mechanic went through the detritus and thinks there could be 2 possibilities, the brown headlights wire chafing on back of alternator although I'm sure it was a good inch away, but who knows what happens in the engine bay when eyes are not looking.

The other, more likely source, was from a very damaged header tank level sensor wire which looked like it shorted on the PDWA brake lines as there is flame damage on the bodywork at that point. Turned on battery and smoke came from that PDWA area again.

Good thing is the car started and ran fine and the lights all work after he cobbled wires back together.
So now I have to tidy it all up and replace wiring.

He did say that fuses on the headlight power feed wires were a good idea and to take both feeds off the battery not the alt


Edit: For anyone following this thread in the future; ignore that level sensor wire was start of fire. Power lead as previously discussed

[KOY 23]

Hi Tanya.
Glad that it was not worse, there's so much power in the battery, very scary.
You mention the level sensor wire that may have shorted and started the fire. It's good practice to have switch wires switching to earth. To clarify using the level sensor as an example, 12v feed to lamp or buzzer, lamp to sensor switch, switch to earth. If there's a short, the lamp/buzzer will operate.
It sounds like yours was wired the other way round, with 12v feed to switch and buzzer earthed, and unfused.

[StagJonno]

Agree with John, above.

On UK Mk2 cars, at least, there's no fusing in many of the warning light circuits and it sounds likely that the HT warning has been tapped into this.

I may be delayed a few days in starting the fuse review - jus realised that we arrive back from NY a day later than I'd thought

Jonno

[KOY 23]

Agree with John, above.

On UK Mk2 cars, at least, there's no fusing in many of the warning light circuits and it sounds likely that the HT warning has been tapped into this.

I may be delayed a few days in starting the fuse review - jus realised that we arrive back from NY a day later than I'd thought

Jonno

IMHO there is less need to fuse switch to earth circuits, if the link from supply to load is a short distance in a safe area, such as dash warning lights etc.

[StagJonno]

IMHO there is less need to fuse switch to earth circuits, if the link from supply to load is a short distance in a safe area, such as dash warning lights etc.

Fair observation, John, until an inappropriate mod is done (eg as it appears in Tanya's case). Or when someone drops the dash for a fiddle without disconnecting the battery (I usually open the battery disconnect, leaving the shunt 5A fuse in circuit so I can listen to the radio). My general philosophy will be fire avoidance rather than overload protection, but being pragmatic, taking account of wire routings. It'll offer an improvement - to get it to "modern" standards would probably need a complete set of new looms.

Jonno

[SaskStag]

Thanks guys, I really appreciate your thoughts.
As far as my car's wiring diagram indicates (I made my own), the power feed currently goes through #3-4 fuse (modern blade) which did not blow and switches to earth. First thing the mechanic said is that fuse should have blown, but when I checked, it was fine. The buzzer sounded when he grounded the exposed wire. Maybe the fuse is not the right rating (can't remember offhand)?
Ignore the strange yellow wire on the diagram, I never did add the RHS transfer housing overheating warning buzzer and those wires are still capped on the RHS of car.

header tank level switch.jpg

Maybe it wasn't that wire, although it was a strong suspect.....

[StagJonno]

Tanya, In my UK Mk2, this fuse is rated at 35A - possibly a bit overrated as a quick calc - wouldn't expect it to go much over 20A on that circuit (assuming that you have filament-type bulbs), though there's be some inrush from the light bulbs - it feeds those for brake, reversing and indicators (I've allowed for hazards as, even though the diagram doesn't show this function, it'll be on this fuse). Also on this circuit are the voltage stabiliser, fuel and temp gauges, and tacho.

An inline fuse at your take-off point rated for, say 5A, would be suitable (should also be adequate for your RHS overheating warning buzzer should you fit this in future).

The PWDA warning circuit is live off the battery to the warning light, then to earth via the PWDA switch. Someone on here (~6 months ago) had the wiring in this area getting hot when he was trying to recommission it. Can't remember what the final outcome was - the only suggestion I had at the time was that perhaps the warning light had failed in a short-circuit mode - very unusual - i think he replaced the light.

Jonno

[KOY 23]

Tanya, In my UK Mk2, this fuse is rated at 35A - possibly a bit overrated as a quick calc - wouldn't expect it to go much over 20A on that circuit (assuming that you have filament-type bulbs), though there's be some inrush from the light bulbs - it feeds those for brake, reversing and indicators (I've allowed for hazards as, even though the diagram doesn't show this function, it'll be on this fuse). Also on this circuit are the voltage stabiliser, fuel and temp gauges, and tacho.

An inline fuse at your take-off point rated for, say 5A, would be suitable (should also be adequate for your RHS overheating warning buzzer should you fit this in future).

The PWDA warning circuit is live off the battery to the warning light, then to earth via the PWDA switch. Someone on here (~6 months ago) had the wiring in this area getting hot when he was trying to recommission it. Can't remember what the final outcome was - the only suggestion I had at the time was that perhaps the warning light had failed in a short-circuit mode - very unusual - i think he replaced the light.

Jonno

Don't forget that Lucas fuses were marked with blow rating, continuous current rating is approx 1/2. Blade fuses are rated at continuous current rating.

[SaskStag]

I think I halved what the ROM says to put in there as glass....15A blade then? I can't confirm as I'm at work

Interesting about the PDWA switch wire, oil/brake lights still worked as it should last night (Mk 1 set-up). New pigtail from LD parts, but a bit fire damaged now.

I do need to open up the dash as my fuel gauge isn't working well................hmmmmmm. Electronic stabiliser. No electric block temp wire, that has been decommissioned since moving to combined oil press/capillary water temp gauge. We found that redundant green wire in the same engine bay corner where the fire was, but no damage on it at all.

A main loom runs along the subframe, not sure if this is spec, from the PO, I had it covered with automotive protection. The mechanic says the wires don't look damaged although the cover was a bit fried, but I will need to go through it all.

The roads here are very rough; you think UK roads are bad! So the car does get a beating and I drive it a lot.

[SaskStag]

After further discussion last night with a few other club members and all your advice; it's back to the headlight power feed shorting on the alternator and level sensor strong collateral damage because they were cable-tied together. Thankyou everyone for your support, I really appreciate it.

So going forward:
Repair all damaged wiring
Re-route that LHS power feed to battery pos
Introduce in-line fuses, especially to heavy-duty power feeds and also into minor circuits

Self-criticism of my response to the fire: To remember I have a battery isolator installed and a fire extinguisher in the car and to use them. I won't always have access to the dog's bucket of drinking water.....