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Hard-Wiring My Tails

Both my brake lights were not functioning again. Before that the whole right cluster went dead; I fixed it by using little strips of kitchen foil stuck to the PCB where it met with the 8-gang connector. You need the precision of a watch repairer to do that correctly. But two weeks ago a Nissan 130Y driven by lady ferrying her kids to school almost rammed my rear end. Our bumpers touched but luckily no damage was done. I knew she couldn’t react quickly because only my third light was working.

So I decided to discard the troublesome PCB and hard-wire my tail lights. It took me two days to complete the project because I discovered the clusters had bulbs of the wrong wattage and it was too late to go and get replacements. The lights for night driving were fitted with two 10W bulbs on each side instead of a 21W and a 5W. Otherwise the job would had been done in a day at a leisurely pace. I am very happy with the results – no more bulb failure warning lights on the dash telling me something was wrong at the back.

If you’re going to attempt the same conversion, here are the stuff and tools you need and the way I went about it for guidance:

  1. Wires of suitable thickness, preferably in 5 different colours, about 2 feet long each colour. The colours are for easy identification.
  2. 20 pieces of large female blade connectors, to fit on the bulb holder blades. Connectors of this size are rather hard to find as electrical shops and spare parts shops seldom stock them. I bought them from a shop doing automotive electrical services at 40 sen a piece. If you cannot get them, trim the blades down with a file or metal snips to accept the more common medium-sized connectors; or just solder the wires to them if you’re good with the soldering gun.
  3. 4 pairs of medium-sized connectors, preferably with a plastic 4-gang connector housing. Either blade or bullet type will work just fine.
  4. 2 ring end connectors for ground.
  5. 10mm spanner or socket wrench.
  6. Philips screwdriver.
  7. Wire cutter and crimper.
  8. Multipurpose cutter/blade.
  9. Small hacksaw.

Troublesome old PCBs taken out.

Bulb holder in the centre had their tabs cut off.

Slots cut at the old bulb holders (centre).

Open up your boot/trunk, remove the spare tyre and the tail light covers. Disconnect the black ground wires from the body and pull out the 8-gang connectors from the clusters. Remove the four 10mm bolts on each side and take out the tail light assemblies so you can work on them on a bench or table.

Remove the bulb holders. This is a good time to check if all your bulbs are working and are of the correct wattage. The top row holds three 21W bulbs and the bottom row holds one 21W bulb at the outer end and one 5W bulb at the inner corner. The hole in the middle of the bottom row of each assembly is meant for the rear fog light and is not used for our market, and it is fitted with a reflector lens on the outside instead.

Remove the bulbs from the holders and keep them aside. Cut off the plastic tabs from the holders with a sharp blade ( I used a small hacksaw! ) and cut a small slot under each of the positive connector blades of the bulb holders where the tabs used to be. This is to allow the blade connectors to bend with the connector blade when you want to fit the holders back to the tail light assemblies.

Next connect the wires to female blade connectors for the top rows, three on each side. Use different colours if available and leave the other ends of the wires free. Shield the connectors with short pieces of shrink tubes or electrical tape as they are so huge they will touch the car body on top. Next connect two blade connectors in a series for the two lights on the bottom row; one set for each side. Make sure enough slack is given between the two connectors and leave the other ends free for the time being. That completes the supply side of the wiring and you should have four on each side.

Right tail light hard-wired.

Wiring done for the left tail light.

4-gang connector

Four-gang connector fitted for easy maintenance.


For the ground side, connect another five connectors for each side in a loop going to each light and ending with a ring connector. You can buy a couple of new connectors or as in my case, re-use the black ground wires from the PCBs which already have the round connectors.

Fit all the connectors to the bulb holders and screw the holders back to the tail light housings. Bundle all the wires with cable ties or electrical tape and route them up nicely to one side. Trim the excess wires and crimp each end to a medium-sized male spade connector. Push each end of the male spades into the appropriate 4-gang connector body. You can arrange them in any order you like; I put them in order of how they are arranged in the cluster, i.e. brake, reverse, indicator and night/parking.

Open up the backs of the 8-gang connectors on each side in your boot, pull out the wires and cut the ends off. Leave the white wires ( two on the left, one on the right ) meant for the fog lights alone. You may want to keep the connectors and the terminals if you to switch back to using the PCBs in future. I don’t think I would. Look at the PCBs and trace which terminal connects to which light. Or you can rip just them off and use the guide below which is given in the order of left terminal number and wire colour, right terminal number and wire colour:

  • Direction Indicators: 4, green; 5, blue;
  • Tail Lights: 6, red; 3, brown;
  • Brake Lights: 5, yellow; 4, yellow;
  • Reverse Lights: 1 and 2, black; 7, black.

Connect each end of the wires to the medium-sized female blade connectors. Remember to crimp up the two black wires to a single connector on the left. Hold the two sides of the the 4-gang connector body together and push each connector end into the connector body until you hear a faint click as the barb on the connector latches itself inside the body.

Make sure that each connector from the harness matches the right wire that you fitted on the light assembly. Test your work and if everything works you should not be getting the bulb failure warning light on the dash. Mount the assembly back on the car – you may have to bend the connectors on the top rows to clear the bodywork – connect them up and re-fit the back covers and enjoy your brick!

Right tail light completed and installed.

Left tail lights completed and installed.

Simple schematic for guidance.


Update Dec 12: After posting this, I found that flags – blade receptacles similar to the female blade connectors but with the crimping ends at right angle to the body instead of straight – would be more suitable due to the bodywork getting in the way.

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About brickwalla

This is probably my [B]ig [230] [F]reaking [T]errible mistake.

Discussion

8 thoughts on “Hard-Wiring My Tails

  1. Need step by step photos for electrical dummy like me, but I do get the general idea….

    Posted by GL | November 17, 2011, 10:22 am
  2. Another update: The Bulb Failure idiot light would always light up whenever I switched on the parking lights or the left indicators and it would go off when I stepped on the brakes, duh! Funny thing is, the indicators are not even monitored by the BF sensor. Apparently, the grounding wire loop that connects to all the bulbs in the tail lights cluster is the suspect. After putting up with it for months, today I took the assembly off and added another ground wire to the loop nearest to the parking lights, crimped a ring connector to the other end and fasten it down to the body using one of the few mounting screws there. And hey presto! It works!

    Posted by brickwalla | April 26, 2012, 5:52 pm
    • I followed your directions and hard wired my 84 240 left side tail light. Thanks for all the engineering work in advance. Standard female spade connectors are .250 however there are a .375 connectors for 12 gauge wire at most automotive parts houses. I found them at Autozone. Since they are for 12 gauge I used 16 gauge, stripped it back long then doubled it over then inserted and crimped. The doubling took the extra space so that the crimping would work well. I removed the circuit board and cut the old connector off leaving the wires as long as I could. I used an electrical tester to find each circuit and the two white wires do nothing so there are four circuits. The bulb holders were trimmed of the tabs with a dremel. The wires all crimped to the female spade connectors and attached to the holders. The wires then were attached to a disconnect, one set attached to the bulbs and the other side of the disconnect to the hot side. Took about 4 hours after rounding up all the parts. Your engineering and instructions cut the time for me. Only thing is that I wish that the bulb holder connectors were at the sides rather than top and bottom side (pointing top and bottom that is) With the connectors at the top and bottom things get really tight when installing the light assembly. My wiring wasn’t as neat as your but once the cover was back in it looks great and the bonus is that the lights now work. Forgot to add, I looped two grounds. One for the top lights and one for the bottom. Crimped and eyelet on both and no problems with the idiot light telling me I have bad bulbs.

      Posted by Bob Kittel | May 26, 2015, 11:25 am
    • Guess I spoke too soon. I grounded everything well, two grounds and tight. The idiot light for tail light out came on. I know to ignore it but why does this happen? Theorhetically nothing has changed. The wires replaced a flat flex circuit and the grounds are in place. The white wire was not hooked to anything so it was ignored. How do I get rid of this idiot lite message?

      Posted by Bob Kittel | May 27, 2015, 5:31 am
      • Sorry for this VERY late reply, Bob. The bulb failure sensor is very sensitive – any difference of resistance between the two sides would trigger it. I suspect the idiot light lights up because you hard-wired only one side of the tail lights. I can be wrong though, old Volvos can be cranky at times.

        Posted by brickwalla | April 1, 2017, 9:04 pm
  3. This is great. Although I think you have miss labeled the pictures of your tail light assemblies that are on your bench. The left tail light you have marked right and the right tail light you have marked left. Not to be picky…… đŸ˜‰

    Posted by Derek | April 4, 2015, 10:45 pm

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