Circuit weak point

[AidanT]

Hi all

 

I noticed that intermittently my reversing lights are illuminated even when the ignition isn't on. (In fact I walked in to the garage and noticed they were lit)

Also when jacking the offside front wheel the horn goes off!!

Don't know if the two things are related but any ideas on where the issue(s) might be?

Aidan

 

[Pete Lewis]

well horn is on a permanent feed so its live all the time  jacking the osf has probably caused some chassis move and the steering wheel is drawn down and is 

making contact with the switch cowl ..blowing the horn.

reverse lamps should be fed froma white wire  /terminal which is ignition switch controlled i suggest 

the feed is being taken from an incorrect supply and the switch has failed ( unless you park it in reverse )

Pete

[Pete Lewis]

just to add the rear lamps claw fittings on Spit/GT6 are a nightmare of mixed up types and designed fittings

some have wired earth  some use the claw

then there is stop tail have offset pin bayonets for twin filiament bulbs  , these can all get mixed up then fit single fil bulbs into twin fil sockets and reversed 

gives all manner of cross feeds bad earths and the rears look more like a xmas tree if say indicators and brakes are applied together 

dont think thats your problem but its easy to sort once you realise of the 3 lights  not all are the same claw holder 

Pete

[NonMember]

1 hour ago, Pete Lewis said:

reverse lamps should be fed froma white wire  /terminal

I think it's actually a green one - the fused version of the white.

[Pete Lewis]

yes , think thats right i was just listening to the lock down and thinking  its ignition switched  somewhere roll on christmas 

Pete

 

[AidanT]

So today started the engine up for it's bi-weekly warm up

No reversing lights - ok fine

After half an hour run, car and garage nice and warm engine off bit ignition on put in reverse..... Still no reverse lights.

Both bulbs gone? Surely not likely? Reverse switch playing silly beggars? 

Any thoughts ??

[Pete Lewis]

I dont do backwards  !!!

switch sounds a good possible , checked all your fuses 

 

pete

[AidanT]

22 minutes ago, Pete Lewis said:

I dont do backwards  !!!

switch sounds a good possible , checked all your fuses 

 

pete

Yes all fuses are fine. Can you get to the switch from underneath or is it a gearbox cover off?

[NonMember]

Although a blown fuse would also take out the temperature and fuel gauges, bad contact in the fuse box is a common culprit, or the bullet connector on the gearbox sub-loom. Another favourite where I live is a mouse having eaten through the loom, usually somewhere over the rear wheel arch.

[Pete Lewis]

and its tunnel out  , not accessible from down under 

have you rechecked the claw fittings are actually eathed

so you gone from lights on  to lights off     thats pretty good going  ha 

Pete

 

[AidanT]

Haha  Yeah great isn't it!! 

I was thinking about the mouse possibility, Is there any feed towards the rear that's perm live? If there was, then that would be more of a possibility and could answer both situations - Even so Tunnel off what ever I guess! Oh fun!

 

Aidan

[NonMember]

53 minutes ago, AidanT said:

Is there any feed towards the rear that's perm live?

Possibly the roof light feed? I don't have the book to hand for the wiring diagram just now.

[Colin Lindsay]

29 minutes ago, NonMember said:

Possibly the roof light feed? I don't have the book to hand for the wiring diagram just now.

That's interesting; sometimes my rooflight stays very dimly lit when all else is turned off; it's an LED bulb so drawing little current but still very slightly illuminated. 

If the reversing lights are staying on something is earthing through the lights, and it's something not ignition controlled as it doesn't go off when the key is pulled - horn being about the only one, unless you have a headlamp flash. I was going to guess that if you have column-switched overdrive it's possible that's where the short is, and it's running to earth along the overdrive circuit, but then it's only the j-type that uses the power from the reversing circuit. 

[Pete Lewis]

you havnt got something crossed into  a night dimming relay ??  adding some havoc 

[AidanT]

1 hour ago, Colin Lindsay said:

If the reversing lights are staying on something is earthing through the lights, and it's something not ignition controlled as it doesn't go off when the key is pulled - horn being about the only one, unless you have a headlamp flash. I was going to guess that if you have column-switched overdrive it's possible that's where the short is, and it's running to earth along the overdrive circuit, but then it's only the j-type that uses the power from the reversing circuit.

If only it were that simple Colin   I have one of two situations, either they are on when I connect the earth (I keep the car battery out of circuit and on a maintenance charge over he winter unless Warming up a couple of times a month), or everything seems fine start the car and warm up everything - Switch off circa 20 minutes later, switch on the ign. and put the car in reverse.... still no reverse lights AAAAGGGGGHHHH. 

I'm just going to have to chase the wiring down but wondered where the best place to start would be - hence the topic title

Pete, blimey that's a bit posh!  No, nothing that complex in the cars wiring - all pretty standard

I traced the wiring diagram and looks that power route is fuse box to voltage regulator (has no impact) to reverse switch then to lights. 

BTW - Does the rear cabling go down the near or off side?

Aidan

Just to add - Not done anything to the electrics on the car for a few years so its not something I have done

[Pete Lewis]

the here is one daft possibilty  which still needs the rev switch to play up but the white feed to the fuse box  from ign switch term 2 is alsoconnected to the voltage regulator via the ign warning lamp   with a brown/yellow ,  could this be back feeding  still needs the main rev switch to be cookoo 

 

tthat fuse as said does also feed the flahers unit, and heater motor 

all a bit odd

[dougbgt6]

20 minutes ago, AidanT said:

Pete, blimey that's a bit posh!

Ah! Ha! You think the night dimmer relay is posh? Mk3s have them as standard, do Mk1s?  I never new I had one, until I found it, "What the **** is this?" It's above the passenger side rear wheel arch.  You have to get the side panel off to get at it. They were intended not to dazzle at night, If you've got one, get rid of it, they're not needed these days.

Doug

 

 

[Jim-GT6]

On 31/10/2020 at 19:14, Pete Lewis said:

just to add the rear lamps claw fittings on Spit/GT6 are a nightmare of mixed up types and designed fittings

some have wired earth  some use the claw

then there is stop tail have offset pin bayonets for twin filiament bulbs  , these can all get mixed up then fit single fil bulbs into twin fil sockets and reversed 

gives all manner of cross feeds bad earths and the rears look more like a xmas tree if say indicators and brakes are applied together 

dont think thats your problem but its easy to sort once you realise of the 3 lights  not all are the same claw holder 

Pete

HI pete,

I'm having a nightmare with my rear lights, and I was looking through the discussions for those with maybe the same issue, when I came to your point about offset bayonets on the twin filament bulbs. Mine are offset, and I'm not sure my holder and bulb are matched. Clearly you know these bulbs and holder mixup issues well, and I think I have a similar mess on mine. I'm just not sure...

1972 GT6 Mk3. First off, the rear passenger-side indicator was intermittent. I kept having to wiggle the holder to get it working, and it would stop again before long. Then it really gave up. I figured it was maybe a bad connection between claw fitting and lamp housing, so I had a good look at a couple of the holders and saw they were all in quite poor condition. The rings with sprung claws were loosely or barely in contact with the connections to the outside walls of bulbs. Ordered a set of six to replace them all across the back. When I  started looking at it, I realised the wiring is far from spec too, but I'll come back to that! I swapped out the reverse light holder (single filament) fine. Came to do the stop/tail, and the old bulb wouldn't fit the new holder. The bulb has bayonet pins that are offset in height, but also offset from centre. One is between the contacts when viewed from the end, the other is not. I've taken some photos to show. The old bulb holder looks like it should take a bulb with pins that would be at 90 degrees to the connections (as does the new one), but the old one does take the bulb with offset pins anyway with a fight, I think because it's been forced?? It's been functional that way since I got it, but not convinced the brightnesses were ever right. Passed it's MOT not long ago though. The new holder is also a different design in other ways. Even the connections don't look like they are configured the same as the old holder. I've since ordered a full set of new bulbs to go with the new holders, as the chap at James Paddock said the bulbs he has in hand have pins at 90 degrees to the contacts and he has never heard of the issue I'm talking about.

This is the bulb that's been in the car since I got it. Trying to show the offset bayonet pins:

The is the new holder I got in the set of six. Matches what they look like in manuals and other people's photos I think. The spade connectors are opposite each other:

And this is the old holder (I've taken the rubber off and can replace). The spades are at 90 degrees, and the connectors don't look to be configured the same:

And now I've blown two fuses, and didn't have any more. So new bulbs and several fuses on the way. All the lights have gone screwy, and I can't test for voltage at the holders when it should be there to see what's what unless I put tinfoil across the fuse. Given I've blown it twice, I don't think I would risk shorting the fuse. I'll have to wait.

Have you ever seen this bulb or holder combo that I've had on the car? Any idea if it's just wrong for the car? Do my new ones look right?

As I say, the wiring at the rear lights is also a mess, but I might save that for another post! Trying to match it to the diagram, but none of the colours are right. I've got lots of picks of that too! Feels like a PO has done some odd things in several places!

[PeteH]

I cannot find a decent copy of what the 13/60 wiring SHOULD be like. there are some "Suposed" ones on the net. but I supect they are for earlier cars (12/50 for instance?).

My Haynes does not cover the 13/60, and the Vittesse manual whilst it give a few clues, again I cannot rely on.

Any idea`s?. As I am at the stage where there is no more  welding to do, so I could proceed to reinstall the loom(s).

As for 21/5 lamps. Most (all?) of the ones I have are offset linearly along the centre line of the bulb holder?.

Per;

Joe Lucas.

 

Pete

Edited March 3, 2021 by PeteH
Replaced Drawing

[Pete Lewis]

all i can add is this problem of mix and not match causes a lot of  lost winking and blinking 

you have fell onto the host of confusion when the whole set up becomes a mess

the 3 terminal needs an earth lead ,  as some need an earth some rely on the claw to earth  more mix up  possibles 

i can only add all my 21/5 offset pin bulbs are 

as you pic   90deg from the bulb contacts  

[Jim-GT6]

25 minutes ago, PeteH said:

I cannot find a decent copy of what the 13/60 wiring SHOULD be like. there are some "Suposed" ones on the net. but I supect they are for earlier cars (12/50 for instance?).

My Haynes does not cover the 13/60, and the Vittesse manual whilst it give a few clues, again I cannot rely on.

Any idea`s?. As I am at the stage where there is no more  welding to do, so I could proceed to reinstall the loom(s).

As for 21/5 lamps. Most (all?) of the ones I have are offset linearly along the centre line of the bulb holder?.

Per;

Joe Lucas.

 

Pete

Yep, that pin arrangement is not what I've got! Side view yes, end view no. And a weird bulb holder on the car which I think looks to have a snapped terminal for either tail or brake circuit. Hoping the new bulbs match your digram. I expect why will!

Thanks!

[NonMember]

1 hour ago, Jim-GT6 said:

And this is the old holder (I've taken the rubber off and can replace). The spades are at 90 degrees, and the connectors don't look to be configured the same:

That's broken. It's not "spades at 90", it's "one of the spades has broken off but the extra third one that isn't on the original fitment (but was on some later models) is still there". The one with the red insulated connector on it in your photo is ground, added because the clips into the housing never worked reliably.

[Peter Truman]

I think non-member is right.

I have a Dolly Sprint with similar rear light bulb holder fixtures, originally the holders relied on the earth thro the tail light body, but as one member said the rear lights were like a christmas tree brake lights brought on tail lights etc.

I realised it was an earth problem and started soldering on earth fly leads to each holder, when a friend who's had multiple saloons offered me a complete double set (6) holders with earth spades on, I believe it was ex a 2500PI, I fitted them with their own interconnected earth loom to a well earthed bolt with double star washers, hey viola all works well no more light scatter. I shouldn't tempt fate but that was 5 years ago! See if you can find a set of separate spade earthed bulb holders, or solder on earth fly wires to each holder but that's a pain!

Doesn't answer the offset bulb lug issue! Good Luck

[AidanT]

Just a quick question back on subject, I notice the wiring harness on Spits are split into Main and Body, Anyone know if it is the same for Mk1 GT6's? Just thinking if the mice have been at my "Rear Wires" 😁, it might be an idea if I could replace  the body harness (if that exists?

 

Thanks

 

[PeteH]

The haynes GT6/Vittesse manual does not show any particular Front rear division. But on the 13/60 Herald you can part front and rear looms Behind the seat panel on the passenger side Rear. Might be worth a look?.

Pete