Technical Brake lights work tail lights don’t

[RobertM]

Hi everybody, you might remember me from “I’m going to drive a Fiat 500 across the country”. I’m on the trip now and I’m on the second day, a few hundred miles in, no real issues. But I noticed that my brake lights work fine, but if the headlights are on it the tail lights don’t work, nor do the brake lights. I still get a license plate light though. I’m wondering if anyone else has encountered anything like that and if I should be looking for a specific fuse that would control those lights or something else?


Other small issues thus far that I’m not worried about in the moment: the car was missing one of the air box clips so the cover ended up popping off causing another clip to go missing and creating a terrible rattle. I solved it by removing everything and putting the filter directly on the part that comes out of the carb, I plan on ordering a few more clips to fix that once we get to Florida. And we had a head light burn out, no bulbs available here for it so that’ll also be ordered once we get to Florida for the week.

Any advise on the tail light situation would be great though! I don’t have time to really diagnose the issue right now, so I might just be avoiding driving too far into the night.

 

[bugsymike]

Hi everybody, you might remember me from “I’m going to drive a Fiat 500 across the country”. I’m on the trip now and I’m on the second day, a few hundred miles in, no real issues. But I noticed that my brake lights work fine, but if the headlights are on it the tail lights don’t work, nor do the brake lights. I still get a license plate light though. I’m wondering if anyone else has encountered anything like that and if I should be looking for a specific fuse that would control those lights or something else?


Other small issues thus far that I’m not worried about in the moment: the car was missing one of the air box clips so the cover ended up popping off causing another clip to go missing and creating a terrible rattle. I solved it by removing everything and putting the filter directly on the part that comes out of the carb, I plan on ordering a few more clips to fix that once we get to Florida. And we had a head light burn out, no bulbs available here for it so that’ll also be ordered once we get to Florida for the week.

Any advise on the tail light situation would be great though! I don’t have time to really diagnose the issue right now, so I might just be avoiding driving too far into the night.

Usually on older vehicles bad earthing or wiring connections cause a resistance in the circuit, often you can prove it by a length of wire from a good earthing point and touching the other end to the bulb holder etc.
Apart from that, on older fuseboxes the connections/contacts are weak and sometimes simply revolving the fuse in it's contacts will show that up. Original brass fuses were better than cheap aluminum modern ones as less prone to corrode.
Obviously a good multimeter is better for diagnosis but this may be a guide.
Another thing to check is if a wrong bulb type has been fitted, such as a twin contact in a single contact holder or vice a versa.

 

[RobertM]

Usually on older vehicles bad earthing or wiring connections cause a resistance in the circuit, often you can prove it by a length of wire from a good earthing point and touching the other end to the bulb holder etc.
Apart from that, on older fuseboxes the connections/contacts are weak and sometimes simply revolving the fuse in it's contacts will show that up. Original brass fuses were better than cheap aluminum modern ones as less prone to corrode.
Obviously a good multimeter is better for diagnosis but this may be a guide.
Another thing to check is if a wrong bulb type has been fitted, such as a twin contact in a single contact holder or vice a versa.

Good tip, I checked the fuses this morning they all look good. I think when I’m back somewhere a near an auto parts store I’ll pull the tail lights out and test the grounding and check it’s the right lamp type.

 

[FR85]

When you press the brakes when the main and sidelights are on does this have any effect in that, if you say indicate to the left while pressing the brake, do both the brake light and signal lights flicker out of time with one another? More than likely a short to ground or indeed a bad grounding.

 

[RobertM]

When you press the brakes when the main and sidelights are on does this have any effect in that, if you say indicate to the left while pressing the brake, do both the brake light and signal lights flicker out of time with one another? More than likely a short to ground or indeed a bad grounding.

I’ll check this in the morning. I’m not sure how it reacts with the signals. But there’s no flickering or anything with the red lights regardless of brakes or not.

 

[FR85]

I’ll check this in the morning. I’m not sure how it reacts with the signals. But there’s no flickering or anything with the red lights regardless of brakes or not.

Then I would "say" it's a shorting issue rather than a grounding issue. On mine, behind the dash two wires coming out of the switch had rubbed together and shorted out but completely killed the car, it was the black wire on the main light switch and one other that I cannot remember, must have been something off the key. But it sounds to me like a live short

 

[RobertM]

So it looks like my problem is actually the connections to the tail light housings and the lamps themselves. I sanded all the connectors down and make sure everything was nice and tight and they're working a bit better. But it got me thinking maybe I should grab new tail housings and lenses. It looks like I can get them for about 35 euros per side. But I noticed there were a few options for LEDs while I was looking around but all of them look kind of tacky and out of place. Does anyone know of any good LED replacements that look like the factory lights? Having some extra brightness and reliability for the tail lights on a small car feels like it would go a long way as far as safety is concerned.

 

[RobertM]

I actually do have an additional question. I'm looking at maybe just getting regular housings and replacing the lamps themselves with LEDs. Does anyone know the bulb type for the tail lights? when I look it up online it just says 21/5w. From my quick bit of research it looks like an 1157 lamp would work but can anyone confirm that before I order them?

 

[bugsymike]

I actually do have an additional question. I'm looking at maybe just getting regular housings and replacing the lamps themselves with LEDs. Does anyone know the bulb type for the tail lights? when I look it up online it just says 21/5w. From my quick bit of research it looks like an 1157 lamp would work but can anyone confirm that before I order them?

We call them lb 380 bulbs (stop and tail) and the single contact lb 382 (indicator), I don't know about LED ones, others here will though.