Hi all,

HELP!!

A while ago my back-up lights (lighting up with the reverse gear engaged...), stopped to work.
Checking up on it I get this weird situation:

a) Bulbs are fine, changed them anyway - no joy!

b) Both bulbs removed - I get 12.36V on either socket! I cleaned them out a bit, just in case. Tried either and both sockets with light bulbs - works fine!

c) Lights work perfect again - for about 20 seconds....
After checking them I switch of the ignition, mount the lights back to the body and check again - no more joy!

d) Now here is what I got at this point:

Both lightbulbs out: Both sockets 12.36V
Plug in ONE light bulb (does not light up!) and the other socket goes to 0.02V! (It did NOT do that initially!). Does it with either bulb/socket...

Now, as far as I can see form the electric diagrams, the reverse-switch on the trans (manual) does NOT control the reverse lights directly, but just feeds into the ECM. ECM then controls the lights.....

So - I am lost!

If I cannot fix this OEM style, I will have to tear into the wire loom and rig something up with a few relays or so.....

Any suggestion/hint/tip appreciated!
(BTW: I don't have fog lights - ....that could drive the reverse lights nuts.....)

Thanx,

thjakits

 

Might help to identify the year/model of vehicle in question.

You might be seeing the result of too much resistance in either the power or ground side of the tail light circuit. With the bulbs out, current = 0 and you see full voltage. But with a light in place, you have perhaps 2-4 amps of current and that may be enough to drop the voltage as you are seeing, V = I x R, so if you had something like 3-6 ohms of resistance (R) in that circuit, 2 - 4 amps (I) would give you a 12 volt drop.

If indeed the ECU is driving the lights, then it's light output may be limiting the current/voltage as well. If that is the case, you might try adding a relay driven off the ECU output, then let the relay drive the lights. The relay coil will only require 0.1 amps of current to turn it on, so that may unload the ECU or the circuit enough to drive it.