l.e.d. outer tail light

Steven Purvis · January 25

Some of l.e.d.s not working on n/s/r outer stop/tail light, tried o/s/r light unit which normally works fine, in its place and it did exactly the same as faulty one,tried n/s unit on o/s and it worked perfectly, have checked wiring and all readings are the same on both sides, hope someone has some ideas as I am at a loss,thanks in advance for any help.

granadaman · January 25

When you say readings the same was you touching one of your tester probes to earth and the other to each posi connection as it could be a earth issue in the connector cable to ground, or did you find the ground in the connector and test from there against each positive. Could just be a broken or corroded earth depends where that light packs picks it up from within the wiring loom. Run a loose cable from earth on the body to the connectors earth see if it then performs normally.

Steven Purvis · January 25

Hi granadaman,thanks for the reply, have checked power and earth at the lamp itself and at the connector about a foot from lamp all good, and the same as the other side, which works fine. All I could think of was if the back lights are run by a module, could it be a fault with that, but have no idea if it has one, have checked on YouTube but no mention of one,by the way its 2008 rx400h. Thanks again Steve.

granadaman · January 26

Herbie on here sent me a link to an rx450h workshop manual you could ask if he has one for your 400h see if you can see where it wires back to

ColinBarber · January 26

23 hours ago, Steven Purvis said:

Hi granadaman,thanks for the reply, have checked power and earth at the lamp itself and at the connector about a foot from lamp all good, and the same as the other side, which works fine. All I could think of was if the back lights are run by a module, could it be a fault with that, but have no idea if it has one, have checked on YouTube but no mention of one,by the way its 2008 rx400h. Thanks again Steve.

There is no module or anything sophisticated, just dedicated wiring for each function back to the body ECU.

1 - Tail light

2 - Indicator

3 - Ground

4 - Brake light

Are the voltage levels the same both sides? You might have high resistance on the ground where is goes onto the body and therefore the light cannot function correctly.

Steven Purvis · January 27

Hi Colin, thanks for the info,car is going to local auto electrician on Monday as I need it fixed as m.o.t. ran out last week,will pass on the info to him it should help thanks again for all the help, will post another message when fixed with info on fault cheers Steve.

ColinBarber · January 27

10 hours ago, Steven Purvis said:

Hi Colin, thanks for the info,car is going to local auto electrician on Monday as I need it fixed as m.o.t. ran out last week,will pass on the info to him it should help thanks again for all the help, will post another message when fixed with info on fault cheers Steve.

Just to add, these rear lights are prone to water ingress as the big rubber cover at the back becomes unstuck which can be glued down again. Therefore the issue might just be moisture, or water has damaged the electrical circuitry within the light unit - although that doesn't explain why the fault stays with the vehicle's wiring and not the light.