I've been told that my 3rd brake light doesn't light up but the dash computer isn't giving me any warnings for it.
Is the 3rd brake light not included in the warnings for blown bulbs? It told me that my left brake light was out and I've changed that.
Seems odd that none of the bulbs in the 3rd brake light are lighting up - sounds like I need to test that it's getting power!
Feed to the high level brake light goes via a connector tucked up above the headlining next to where the rubber tube goes between the body and upper tailgate. Might be worth looking there first.
The middle brake light doesn't give a fault warning - its possible that all five lamps have blown. Mine started working intermittently, and it turned out to be the crimped/riveted connections used to attach the wires had come loose. Soldered the wires on and all is well again... except for one of the lamps that has actually blown.
I’ve had one with all bulbs blown, it’s not unusual, also had with just bad connections
Ok...so I got the multimeter out and tested the light.
All the bulbs are good and the light unit is getting just under 12V - dead lamp?
PRC7644 should be what I'm after, right?
Taking it out and attacking it with a soldering iron would be much cheaper.......
If your getting 12 v then it’s a connection problem, get some sand paper and lightly clean the bulb bases, where the bulbs touch the side and check any wiring, also have you tried putting direct feed to check it over
Jeez, just seen the price of these, I’d definitely be playing before I wasted 50 quid plus on a brake light,
There’s not much to them after all
I figured there wasn't much to them. There's no visible corrosion on either the board or the bulb holders.
I tested the power where the wires are soldered to the board and I tested the continuity of the bulbs while they were still in the bulb holders.
The lines on the board that go from the wires to the holders are nice and thick and clean with no visible breaks or corrosion etc.
I'll take the whole thing out of the car tomorrow and take a closer look. It does look like a really simple component.
I’m trying to remember when I had problems, I’m sure it was the earthing of the bulbs, I think a lot of it is the bulbs nowadays, they don’t seem to have the quality of previous ones.
Did you try the bulb positive ?
The connectors from factory are wires crimped on to ring crimps, then riveted to the PCB - on mine, these appeared totally fine... a slight movement of them and out went the light. There might be voltage when you measure with a meter, but was that with lamps in? Connection might be so poor any load pulls the voltage down.
Soldering the wires straight on sorted mine. Quite frustrating as I kept being told the lamp was out entirely, but when I checked... it was working.
Just pulled the whole thing out.
Tested continuity across the rivetted/soldered on terminals with all bulbs fitted - has continuity.
Tested with no bulbs fitted - no continuity.
Tested with one bulb fitted - has continuity.
Moved the bulb to all positions and tested each one - has continuity.
Removed all bulbs from bulb holders and tested the holders - no continuity.
Tested all holders with bulbs fitted - has continuity.
Tested all bulbs out of holders - has continuity.
Tested pins in connector with no bulbs fitted - no continuity.
Tested pins in connector with one bulb fitted - has continuity.
Tested pins in connector with all bulbs fitted - has continuity.
Tested power at the car connector - has power.
Plugged it back and it works...
Intermittent high resistance connection. By pulling it out you've moved something so now it works. Question is, for how long?
That’s a P38 for you, mysterious
Gilbertd wrote:
Intermittent high resistance connection. By pulling it out you've moved something so now it works. Question is, for how long?
Until you really need it, obviously! :P