The Triumph Dolomite Club - Discussion Forum

For no apparent reason, the rear off side indicator has stopped working both in indicator and hazard functions. It's not the bulb as this illuminates in one of the 3 working units.
I thought flasher unit problem but surely both wouldn't fail at the same time?
Any obvious thoughts (bear in mind my car electrical knowledge is v limited!)

James (Dolomite Sprint - LKN 10W)

Probably a bad earth in the bulb holder or when fitted to the light cluster, try giving it wiggle when fiited to the cluster with the indicator on to see if it starts working. If you have another bulb holder try swapping it.

Not quite sure what you mean by the other 3 working units, but if any of the places or other bulbs in the same tail unit work, it can't be the earth connection to the unit itself. If the front one is flashing, it's not the indicator switch or wiring to the flash unit.

If its not the earth to the unit, it'll be the wire to the rear dimmer (if fitted), the wire to the bulb socket, the connections between the bulb and socket, the internal connection between the bulb holder and the prongs that fit into the tail unit (which is often bad on the gRimmer replacements), or the connection between the prongs on bulb socket and the body of the tail unit, which can get corroded and lose contact.

If the dimmer is fitted and wired in, that's well worth a good coat of looking at.

You probably need to use a multi-meter to check there's the strobed 12v being fed the to the bulb.

First off, I would take the bulb holder out of the tail unit, and with a good bulb in and the ignition and flash switches on, see if there's there's a voltage between the body of the bulb holder and any good earth on the car. If there is, double check by earthing the bulb-holder body with a wire, when the light should flash. If that's okay, it's the connection between the holder and the unit or the unit and chassis earth.

If there's no voltage on the holder with a bulb in, etc., take the bulb out, and check if there's a voltage on the feed to the bulb - be careful not to short the multi-meter probe to the bulb holder body. If there's no voltage there, you'll have to work back up the wire through the loom at each connector to find the break. In such cases I've been known to splice a new wire in under the dash (where it comes from the indicator switch), run it the length of the car, and splice it to the feed to the bulb holder before now - just as a temporary fix of course.

Here's a not very good scan of the wiring diagram and key for a Sprint to 76. Should do for this job even if yours is later.



Graham

As Tony has already stated one problem that can occur is that the earth connection within the bulb holder can corrode and you loose the earth path. I have previously highlighted this problem in Dolly Mixtures so I do have a photograph to hand that indicates the problem and shows the simple way to resolve it by cleaning the area and then applying solder to the joint. I have had to do this to some of my bulb holders and I keep meaning to do to all the rest of my rear light bulb holders before the problem develop in them.

Thank you for the help so far....I made a temporary connection between the working and non-working rear indicators, switched on the hazards and the non-working light started flashing.
the bulb, holder and earth would therefore seem OK so presumably a power feed problem.

Graham's temporary (likely to become permanent) solution would seem to the the way to go but i am not quite sure where to take the connection from. From the wiring diagram, i think i am after the green/white wire from the direction indicator switch. Probably a stupid question but where would be the best place to splice a connection?

James

As a temporary fix, I'd put a scotchlok on the wire on the car side of the connector from the turn switch under the dash. That's (on my car) the 9 way connector, 8 of which are used, that's the mating half to one of these:

Though I think the ones on the car are translucent, not white - this is a spare I saw at a price I couldn't not pay.

I know that not everybody likes scotchloks, but I think it will be easier to use one of them than cutting the wire and putting in a new connector or pushing the pin out of the original one, cutting it off, and crimping in a new one with the extra wire. All of that done while under the dash. And it's only a temporaryish fix.

The risk is that the damage to the insulation could physically weaken the wire so it breaks after the scotchlok has been removed. So I'd add it in a good distance down from the connector, so there's some wire to access in a repair.
The other risk is that it's that connector that's duff.

Graham

Green/white is indeed the colour code you need to track. I'd start at the back and work forward with a simple test light.

There are a couple of trouble spots (besides the hardy perrenial of the dodgy bulb holder earth) that are worth checking more closely. The first is in the N/S/R corner of the boot where folk have scotchlocked in connections for a towbar, look for bare wire and slits in the insulation of all wires in the loom near the n/s tail light. If you find a break here, it's fairly simple just to join the 2 broken ends together. A car as late as yours is unlikely to have a night dimming relay fitted so you can probaly forget that.

The second is harder to track as it's in the loom where it crosses the N/S rear wheel arch, I have a handful of front-to-back looms here (good source of spare wire) that exhibit burning in this area from weld repairs done to the arch without moving (or not knowning about) the loom's presence in that area. Best to check at the junction block adjacent to the n/s/f door post for a circuit either side of this plug. If you have power at both sides of this plug but not at the tail light this will almost certainly be the case.

Whilst I would consider a jumper wire a good temporary solution in this case (i'd take the jumper on a scotchlok from the rear side of the A pillar plug) it really is advisable to pull the loom into view, because if 1 wire is melted/broken the others won't be far off!

Steve

Carledo wrote: ↑Fri Jan 01, 2021 10:12 pm I'd start at the back and work forward with a simple test light.

The problem is how to access the conductor in the wire, except at the connectors, without damaging the insulation and risking damage to the conductor. Sticking a dressmaker's pin in to contact the conductor can work, but it's literally a bit hit and miss. If you've a multimeter with a resistance range or continuity tester, in addition to checking for supply voltage on the front side of a connector, you can check for connection to earth, through the bulb, on the back side (mum, he said backside) of the connector. Alternatively, once you've spiced in a temporary wire from end-to-end you can, like Steve suggests, test for voltage on both halves of the connector.

The pins on those connectors have two wings that stick out of the brass tube to lock them into the body once inserted. Ideally, the right inside diameter tube will fold them in and the pin pulls out easy. Failing the tube, you can push in each wing in turn with a watchmakers screwdriver and wiggle the pin out.
Both sexes of pin were available on ebay the last time I looked. So, if you find a section of wire is bust, or a dirty pin that won't clean you can replace just the wire from connector to connector or the pin with no scotchloks to make bumps in the carpet. Get a good crimp tool and enough pins to allow for mistakes though. I can post pics of the crimpers I've found to work if you want.

Graham

By way of an update, I ran the jumper wire from a scotchlok connection under the dashboard back to the rear light. It all now seems to work albeit I accept that this is addressing the symptom without tackling the real cause.

Out of interest I recall exactly the same problem - O/S/R light not working - on a TR7 some 30+ years ago which was cured in a similar manner. It was an easier fix in the TR as the cable didn't have rear seats to cross.

I did look at tracing the cable and solve the real problem but it was cold, I don't really know what I am doing and everything is caked with in Waxoyl / Ziebart or similar. Probably a straightforward job with someone who has done it before.

Graham / Steve - thank you for your help.

James