Weak tail/stop light - One side dim, earths are fine

Tor

Tor

Well-Known Member
Hi all,

I've been troubleshooting my NS tail and stop light (LHD), which have grown weak over the last month or so, to the point where there's a faint glow. I've tried replacing the bulb, checked connectors and socket, checked the earth inside the boot and on the tail light cluster itself. They were pretty bad but there's no improvement. The indicator is bright and works as it should. Reverse lights are out due to faulty switch.

I've tried the fuse box, swapping around, checking connections and so on. I'm at a loss. The car came out of storage in a moist, disused coastal cow stable this summer. Miraculously she's not eaten up by rot but the electrics have suffered (along with brakes, exhaust, clutch, bushes etc.) having not seen daylight since 1995.

-Also had a dim L.H. interior light, and I thought the two units could possibly be connected by a common earth... Turns out the bulb was blackened; super-heated but pale. Replaced it, problem solved.


Best regards,

Tor

(1974 V8 ex-auto, Volvo green, Britax, LT77, Sundym, Armstrong steering, wobbly steel wheels and some mould)
 
firstly what u need to do is to check and see how many volts you are getting at the rear of the car..if u get 12 volts then that will discount out the main feed wires to the bulbs..(check the stop lamp switch as its proberbly got rusty inside)

if u have good volts at the rear it can then only be the earth at fault..you could also run a new earth wire from the rear lights to a new clean earth point..
 
Hi Jay,

I get 11.6 volts (engine off) on the weak side, 11.4 on the good side, so it should as you say be an earth issue. Also, the brake light switch is a replacement, rerouted inside the car on the pedal box. I checked the connectors but I'm thinking a problem there would affect both sides.

I'll try running a fresh wire to a new earth point at the back. But as long as the indicator is bright doesn't that mean the cluster is properly earthed? Is there any other connector I can check?

Tor
 
cant remember off hand tonight if the earth is seperate for all the bulbs..but try a new earth lead from the bulb on the dim side(put the wire on the earth bit of the bulb)the cluster can corrode round the bulb holder making a bad connection.
 
Single earth connection to the cluster, but I was just going to say what Jay said, check the actual bulb holder area hasn't corroded.
Also I find having a tin of contact cleaner Contact cleaner at Maplin and spraying plenty in, then working the bulb / connector in and out a bit often works wonders.
 
Had a similar problem myself (a day before the Mot!).

Check the bottom of the holder, this is spring loaded and occasionally the spring can slip on the contact pad, the result is a poor contact. The soldered contact tab to the bulb can corrode too.

Carefully though, they are fragile.

A good clean with contact cleaner and a high grade wet and dry (1800 grade very gently!) can shift enough grot to get a good connection.
 
Hi all,

Thanks very much for your replies. It does look like a single earth for all sockets. As Jay suggests the bulb holder area (at rear of cluster) is quite corroded at the base. I'll try jamming a wire in down the side of the bulb and earthing that to see what gives.

Inside the socket looks fine, tabs have no visible corrosion, and the spring is firm. It's the outside that looks bad. No Maplin's stores in southern Norway but I have a generic oxide cleaner that should work! I'll fill you in.
 
Follow-up:
I undid the tail light connector and tried it with a working bulb (I've tried several) against a solid earth and got the same dim glow as before.

My next point to check will be the fusebox. So far I've only switched fuses around and pinched the connectors. There's a warning buzzer fitted to one of the circuits with those blue clip-on connectors and I'll check that out as well.

Does anyone know of leads "suddenly" failing, ie. in the course of about two months of driving following long-term storage? I'm getting bleak visions of having to run new leads.

Regards to all,

Tor
 
maybe the insulation could have rubbed through somewhere along where the loom is maybe near the rear light??
 
I haven't had any indication of that but I'm going to have a closer look at all of it...

Tor
 
Issue resolved! Replacing the cluster for a tidier one gave me the bright light I wanted from the bulb that came with it. Just to check, I swapped the bulbs around, and it was my old one (and at least two others) that was faulty.

*As I write, I've just finished reading the inscription on the bulb. It reads 24V. It came in a pack from a petrol station. I never thought to look! :O
 
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