Reverse light & New Caterham Light Kit

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Jonathan Kay
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"Questions

1. would this switch work with the new lights anyway?

3. If all else fails I am thinking of changing the switch to the normal 2 pin and rewiring. Any ideas on the easiest way to do this."

...

"Let's confirm what you've got, as above. Then look at the options. NB LED units usually have to be connected the right way round."

...

Assuming that you've got that earth-switched arrangement what wires have you got emerging at the rear end of the car? And what are the relevant wires on the new lamp unit?

Jonathan

Ralph
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Thanks Jonathan

Went through your suggestions and I now know what is going wrong.

Sometimes you lose you way and it helped to read your post and made me think logically.

As suggested I rewired an old lamp back and took the connection of the switch and ground to the gearbox. (Light came on !). Re connected the connector to switch and light came on (Puzzled).

Used a circuit tester and the answer to the why plunging in to the new loom does not work is now apparent the original connection on the old loom is back to front to what I would expect (In the Picture the wire with the masking tape is black (This is the live wire the green is earth). see photo

I always thought Black was supposed to be earth?

So I assume all I have to do is swap the pins round in the plug so live connects to the green wire on the new loom plug.

In the new loom you only have one wire for both the Reverse light and the Fog Lamp so assume the earth is within the new units.

My car is 1996 and uses the Econoseal type connectors. Also I had to run the new loom along the chassis at front of the fuel tank as the gap is too  small at the back (not enough room to feed new Reverse Light / Numberplate light through). If you have a newer car as Stu said in his post you might be better off taking the boot floor off. 

Thanks all for chipping in as it helped a lot.

 

 

John Vine
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(Puzzled)

Perhaps reverse was still engaged?

So I assume all I have to do is swap the pins round in the plug so live connects to the green wire on the new loom plug.

Or swap the green on the new connector, moving just one pin rather than two!

JV

ScottR400D
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Possibly a little late but for what it's worth I ran the new loom on the top of the fuel tank away from all the crap. As you say the new reverse/plate light connector won't fit up between the tank and the back panel, but it's simple enough to remove the connector, feed the wire through and refit. 
 

Jonathan Kay
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"Used a circuit tester and the answer to the why plunging in to the new loom does not work is now apparent the original connection on the old loom is back to front to what I would expect (In the Picture the wire with the masking tape is black (This is the live wire the green is earth). see photo

"I always thought Black was supposed to be earth?"

I'm not quite sure what you're seeing, but it sounds like progress. Please document it all and keep us informed. : - )

"Standard" colours:
Black should be earth.
Green should be live switched with the ignition.
Green/ Brown should connect the reversing light switch to the reversing lamp.

From Caterham's wiring diagrams:

Reversing light switch with one connection:
(And this must be a switched earth)
Green/Brown from reversing light switch to reversing light
... so the wires from the chassis loom to be connected to the lamp unit are Green and Green/Brown.

Reversing light switch with two connections:
Green to reversing light switch (so this is a switched live)
Green/ Brown from reversing light switch to reversing light
... so the wires from the chassis loom to be connected to the lamp unit are Green/Brown and Black.

Please could you check if one of your original wires is Green/Brown rather than Green.

Thanks

Jonathan

Ralph
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Hi Jonathan

Also this may be useful to anybody else who has the same single wire reverse light switch as me

DOUBLE CHECKED EVERYTHING

1.Single wire from loom to g/box Green with Brown strip

2.Connector at rear of car is 2 wires one Green/Live & one Green & Brown Earth (Could hardly make out the brown stripe).

3.I moved the position of the connector pins so Green now connects to the green wire from the new loom.

GOOD NEWS Reversing light works

BAD NEWS Reversing light stays on when not in reverse.

My Conclusion would be if you have a Reversing light with one connection you will have to change the switch to a two pole type and earth the second pole to part of the car. If you want to fit the new Rear Light Kit

Would like to hear which switch to buy as not much room to play with in-between chassis and Type 9 G/box

Jonathan please shoot me down in flames if you think I am on the wrong track.

Jonathan Kay
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You might not need a new switch (and the related new wiring). That sounds as if the lamp unit is getting an earth connection all of the time, rather than only when the switch is closed.

First disconnect the lamp unit and check whether the Green/ Brown wire from the chassis loom is connected to earth all of the time rather than only when the switch is closed.

But if that isn't the fault:
I don't know how the new kit is wired... but I'd investigate along these lines... is the lampholder earthed other than through the Green/ Brown wire... is a common earth wire shared with another part of the lamps, possibly in the new subloom... etc.

Jonathan

OldAndrewE
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You should not need a new switch unless the old one is faulty.  Both new and old lights have a 12v supply that is energised when reverse is engaged (with ignition on) so as long as the new light is connected with correct polarity then it should work Frown .  I assume the old light worked correctly

Andrew

1985 S3 1700 XFlow.  Undergoing full restoration

Jonathan Kay
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"You should not need a new switch unless the old one is faulty.  Both new and old lights have a 12v supply that is energised when reverse is engaged (with ignition on) so as long as the new light is connected with correct polarity then it should work.  I assume the old light worked correctly"

AIUI Ralph has a gearbox switch that switches the earth side, not the 12v live side,

Jonathan

John Vine
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If it helps, here's my understanding of what's going on ( I hope this is legible).  Please shout if I've got something wrong!

Ralph's wiring is on the left (switch-to-earth at gearbox).  Top left is what he started with, and bottom left is after fitting the LED kit.  On the right is the later 2-terminal reversing light switch, before and after fitting the LED kit.

The reversing light (R/L) connector in the kit has just one wire (green).  This connects at A, but ends up with a circuit via the R/L earthed at both ends.  

Ralph then moved the single green wire to B.  This lights the R/L ok, but with or without the R/L switch.

If I'm right, I don't see any way of avoiding the need for a 2-terminal R/L switch.  However, CC claim that the LED kit works with all models, so something doesn't stack up.

JV