tachometer & reverse lights not working

[sacbmwdriver]

After installing a sub/amp, I've noticed that my tach and reverse lights not working. I have checked all of my fused and they seem to be all good, I dont know if the two are connected in some way besides the fuses. Anyone have any insight on this? or had this happen?

[Gregs///M]

After installing a sub/amp, I've noticed that my tach and reverse lights not working. I have checked all of my fused and they seem to be all good, I dont know if the two are connected in some way besides the fuses. Anyone have any insight on this? or had this happen?

Fuse 10 powers both the tach and back up lights. Replace it with 7.5A.

[sacbmwdriver]

Fuse 10 is good, everything else works I don't know where else to look.

[Gregs///M]

Fuse 10 is good, everything else works I don't know where else to look.

How do you know the fuse is good? Visual check or multimeter check is not the best method. A test lamp or replacement is the best. 20+ old fuses can develop micro cracks which can expand with heat (increased current flow) and cause intermittent operation.

Other than that, you might have damaged wiring or insulation. Your tach could also be dead SI board batteries but that will not cause your reverse lights to not operate.

Another possibility is the switch for the back up lights could be loose or bent, thus not triggering the lights. Check the ETM manual for your car to help you troubleshoot those circuits.

[StereoInstaller1]

In addition to the above, the wires that lead to the reverse switch often fail under the car, just below the shift boot

[sacbmwdriver]

I tested the fuse 10 with a test lamp and also switched it out with another 7.5a fuse just to see, still doesn't work, I just thought that the tach and reverse were related because both stopped working after I installed my sub/amp. I guess I've got to dig deeper

[sacbmwdriver]

We'll, the tach decided to begin working again on it's own, I think I've got some type of electrical gremlins lol. But I'll take a look at the reverse switch wiring

[StereoInstaller1]

Got to love self repairing electronics! You might wanna talk to Greg, he does that sort of thing...but on the switch wires, pull up your shift boot and then the rubber boot under that, you will see the evel wires I refer to.

GL!

Luke