Electrickery advice / help needed

[Hawk]

I stumbled into the garage last night to grab another beer and was met with an eerie glow coming from my TR (see pic).  Having been out for a spin earlier in the day, the roof was down and I believe it was this that has allowed me to see a problem that I had not previously seen.......the interior lights being on. 

Full disclosure:

1 - I am a muppet with electrics (and so please talk to me as if I am capable of little more than changing bulbs or putting a multi across battery terminals!)

2 - I have had a an intermittent (maybe 3 times a year) issue with the fuse that powers lights, OD and gauges blowing

3 - coming home from LMC last year, the interior light flashed on a couple of times when going over bumps (only visible at night) - I looked for problems with the wiring but nothing obvious and I haven't noticed since.

And so some questions:

* - the car is hooked up to a battery tender so no issue with battery being drained but am I right in thinking that removing the bulbs will remove any power drain?

* - are these lights supposed to be on a live feed so powered at all times? 

* - is this on the same fuse as OD etc?

* - any thoughts on where the issue may be?  I have tried to follow wires in loom and cant see any obvious bare wires but a few pointers as to where I should look would be appreciated.

Thanks

 

[RogerH]

Hi Hawk,

              I think there should be switches on the door that turns the footwell lights off when the door is shut.

have a look here at the Purple/White wires  http://www.advanceautowire.com/tr2506.pdf

 

As for the other issues I'm not going there

 

Roger

[stuart]

It maybe that your door pillar switch is failing and shorting to earth hence the lights on, they are live all the time.

Stuart.

[brian -r]

I would disconnect the wires at the door switches first .The feed to the lights is permanently live and the circuit is made by the wires from the bulb to the switch being connected to the negative supply by the switch earthing to the body. 

For the lights to stay on the negative wire from the bulb must be connecting with the car bodywork at some point. If the fault was in the live positive wiring the fuse should blow.

If disconnecting and insulating the wires at the door switches does not fix it , your problem will be in the wiring between the lights and the switches.

Brian

[Waldi]

Hi Hawk,

the interior lights are fed from a “constant feed” so not via the ignition switch. The “switch” is the little thing in the door A-post; when this is operated you make a connection to earth, current can flow through the lamp and it glows. i worn insulation that shorts this wire to the body will give the same result.

As you can see in the diagram that Roger forwarded, the purple wires have their own fuse in the fuse box. You can actually check if different- colored wires are connected to that side of the fuse, but the OD wire (feed) should not come from there.

If you remove the bulbs you will stop that source of drain, but there may be others.

A relative simple method to measure the current draw (loss) when everything is off is as follows: 

a) simple way:

switch multimeter to “amp” and put red wire in amp connection.

remove battery pos lead and put MM between battery + and pos (red) lead.

You can now measure the current draw. Be carefull: most MM can only handle 10A, so do not start the engine or switch on heavy consumers (like a Bosch pump), so best to    NOT switch ign/contact “on”.

if all ak, it should be less than 0,05A, as a course indication. With 0,05 A continuous loss you will drain around 1Ah per day (24x0,05=1,2Ah), so over several weeks that adds up.

Hope this helps.

Waldi

[Hawk]

Thanks all - really appreciate the pointers.

I am away with work for a few days but will have a play over the weekend and report back.

[SeanF]

Hi Hawk,

I had this same issue with my 74. I noticed it when I was wiring up the interior lights during my rebuild.

My new loom from Autosparks had a metal bulb holder for the passenger footwell light. Once this had a bulb screwed in, the metal casing became "active" and if I inserted the case in the bracket under the dash it earthed and the interior lights (both sides) came on whether the doors were open or not. If I left the bulb holder hanging and not earthed to the dash, everything worked normally.  I put this down to a faulty bulb holder but I was only guessing.

I solved the issue by swapping out the metal bulb holder for the old plastic one from my old loom and everything has worked fine since.

This may help you. To test if your issue is the same unclip the pass. bulb holder and see if the lights go off.

Cheers

Sean

[Hawk]

Thanks Sean but I don't think I have the same issue as the bulbs remained lit when I pulled them from the bracket.  It is not clear in my pic but the bulbs are hanging down. 

[tr graham]

as said before  your bulb holder carries a constant live + feed , so the holder is either receiving an Earth - from the door switch when closed insead of open or the feed wire from the door switch is making a Earth - between the switch and the holder.

graham