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TR3a hardtop earthing.


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Forgive this numpty question. But I really don’t get electrics.

 

i am fitting a steel hardtop to my old TR3a. It is held on to the car by 5 metal thumb screws at the rear clamping the painted brackets. That screw into metal bracket bolted to the car body.

 There are also 3 bolts clamping the painted hardtop to the windscreen which is in turn bolted to the body. 

I am fitting 2 interior lights with simple on off switches over the door apertures of the hardtop. I am taking the live feed from the rear light (my thinking is that I’ll only need interior light in the dark when I’ll have at least sidelights on) the lights have an earth lead and also appear to earth via a mounting screw.

i am also going to fit a high level brake light in the hardtop rear screen. Again the live feed is from the live feed from the cars rear brake light.

i will be fitting a male / female plug arrangement to connect the live feeds between the car and the hardtop. ( interior lights live combined and the brake light feed thus 2 pin)

my question is can each light be earthed locally to the hardtop ?

and

do I need an earth bridge between car and hardtop so a 3 pin plug. Or are the bolts between car and hardtop enough if I remove some paint on the brackets ?

so I just have the 2 lives in a 2 pin plug ? Or 3 pin with the earth ?

  

hope you can understand my thought process. 

 

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In theory, your system ought to work without the need for a separate earth connection.

However .... !    As an Electrical Engineer, I would favour an earth wire at each lamp, daisy chained and brought to your male/female plug arrangement. 

All the electrics on my TR4 have a separate earth wire for each device, because the technicians in the Competitions Department wanted to ensure that lights etc would continue to operate properly in the most arduous conditions.  And, after 57 years, everything still works properly with the original wiring (plus my own additions and modifications, of course).

Easier to install such an arrangement now, rather than have the possibility of one or more of the extra lamps flickering or failing at a later date.

Ian Cornish

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Hamish,

A hard top and interior lights ???

What next, air conditioning?

To answer your questions, I see no problem with earthing the lights locally to the hardtop, but for reliability I’d put an earth from the hard top, via a 3 pin plug, to some reliable earth on the car body.

Yes, in theory there should be an earth from the hardtop to the body via all the fixing screws, but because they will be disturbed each time the hard top is taken off and on, I’d go for the belt and bracers approach. It will do no harm.

 

Is the fuse/wiring man (“Person“) enough for two extra lights off the sidelight circuit? I would guess so, but if you go for LED lights then the extra consumption is negligible.

Just realised that Ian beat me to it.

Charlie.

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Thanks for the replies. 

I should have mentioned the additional lights are LED. 

I’m using these:-

Chrome Interior Lamp Light On / Off Switch BHA5138 + LED Bulbs ROVER P5 https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F202182245258

 

12V 5 LED High Mount Brake Stop Light Bar Beam Rear Tail Lamp Car SUV Truck  - https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F183761124510

 

Charlie.  All the extra lights / wiring is to sort of future proof the hardtop refurb. Better to wire it now rather than later if the headlining works out and is successfully (!!!!!!!!) fitted.

the brake light is just because there will be a rear window to fit it to for safety. 

( just thought I could fit a rear led light/ brake light to the roll bar and use the same plug arrangement to the car feed. Hmmmmm)

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Hi Hamish,

I would run earths, after all you have one wire going to the lamp,

little effort in doubling that up, and wait and see if the bolts clear of paint transmit the earth

and if not simple to bridge,

john.

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hi hamish,

You may run into probs with the plod due to single light,  OK it was as original on the early 2's but as an extra not so sure!!!!

Would be worth talking to someone from Traffic dept to check that you wont run foul of a roving officious patrol car. They sometimes take delight if they are bored.

As a point of interest I had one fitted inside my 3a with a hood and the glare reflected off the rear window was very distracting. My may find the same on a perspex rear window on the hard top.

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Isn't it ridiculous, £3.41 plus £1 postage to UK from China for a high level LED brake light. I was very  happy to have paid about twice that for the same or v. similar thing that I am sure is a big safety improvement.

Tim

3rd  Brake Light.JPG

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3 hours ago, Rodbr said:

. . . the glare reflected off the rear window was very distracting. My may find the same on a perspex rear window on the hard top.

Roof mounting it externally is another possible avenue, for a hardtop at least. 

(Not sure if this particular example is a commercial product, or bespoke Sawzall / air scoop combo? :) Smart though, either way.)

TRtopA1.thumb.jpg.1dd0a0a2f054cdad3df8e74cb328d8c7.jpg TRtopB1.thumb.jpg.2f79e7b4410e944ae7a1471d1d72b448.jpg

Cheers, Deggers

Edited by Deggers
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Or, just replace the numberplate lamp with the sort used on TR2/ TR3. (Lucas L525) Stick one of my special LED bulbs in, & job done :)

Bob.

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The rear brake light sticks to the window so I hope it doesn’t glare too much. 

I was going to stick it to the bottom of the screen as that’s easiest for the wiring concealment. But looking at Tim’s picture at the top May be more visible in  modern traffic esp as the hard top will be used in less good conditions.

deggers option looks good but would require invasive drilling etc of the hard top. But with modern LED technologies could be used as a bright reversing light as well which would be useful.

sorry bob didn’t think of using the L525 and it’s a bit low for a high level brake lights.

 

 

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Hamish, I used a piece of strategically placed thin black ABS sheet to prevent any troublesome reflection from the rear screen. A tiny bit of light bleeds round the edge but that's fine, it's not distracting and serves to confirm the light is working. For some reason when I try to upload only a 217kb image showing the actual light installation it fails. I used two pieces of 1/2" wide thin steel sheet suitably bent to support the light snugly against the rear screen while the ends of both strips are tucked under the substantial glazing rubber and held securely. I used very thin domestic alarm wire which was easy to conceal under the rubber. 

It must be better to place the light at the top of the screen, after all it's meant to be a "high level" brake light. I followed a 2.5PI saloon on recent event and a third brake light was fitted at the base of the rear screen which rather defeated the object since it was not a lot higher than the existing brake lights. For me the real benefit of my 3rd light is that it has a sporting chance if being seen through a Chelsea tractor when I have one immediately behind me that completely masks my factory brake lights from the view of a following driver.

Tim

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32 minutes ago, tim hunt said:

For me the real benefit of my 3rd light is that it has a sporting chance if being seen through a Chelsea tractor when I have one immediately behind me that completely masks my factory brake lights from the view of a following driver.

Tim

+1 to that sentiment.

which is why I’m thinking of a stick on led bar to my Roll bar that can utilise the same plug arrangement for when it’s topless. 

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