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Backup Lights, Side Mirrors and LED bulb issue.

 
Old 03-21-2019, 05:39 PM
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KenRudd
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Default Backup Lights, Side Mirrors and LED bulb issue.

What, if any, is the circuit relationship between the reverse lights and the side view mirrors?

Background:

Yesterday I had to get my car through state inspection and had a detailing scheduled. I noticed my left rear backup bulb was burned out. All I had was an LED bulb to replace it, but it lit up, no warnings and it got me through inspection.

Then I had the car detailed. As is common when washing the side mirrors, they knocked them out of alignment. I went to drive my car and then tried to electrically adjust the mirrors, no dice, just a very faint click from both left and right.

Great, I was pissed. My detailer somehow broke both my side view mirrors. But I figured I would check the simple things first, fuse or relay. Fuse is #12. But I looked closer on the fuse chart and Fuse 12 says Backup Lights, Mirrors. So apparently the mirrors and reverse lights are on the same circuit, and the fuse is good.

So this got me thinking, do the mirrors require some current flow through the backup lights that an LED bulb is thwarting? If so, why does a burnt out incandescent bulb not cause the same issue? I have not picked up a new/good incandescent bulb to swap back in yet, but I am puzzled.

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Old 03-21-2019, 05:50 PM
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Randy V
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If it was me, I'd hop over to PepBoyz, get a replacement backup bulb, see if it fixes it them then move on with life.

But I'm not the curious type.

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Old 03-21-2019, 06:18 PM
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KenRudd
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Originally Posted by Randy V View Post
If it was me, I'd hop over to PepBoyz, get a replacement backup bulb, see if it fixes it them then move on with life.

But I'm not the curious type.

This is actually my post-work plan today, but I am the curious type.
To quote the great Emil Faber: "Knowledge is Good"

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Old 03-21-2019, 10:02 PM
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KenRudd
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Incandescent bulbs back in, no change. Slight click when I toggle up-down. Nothing side to side. No motion either way. Both sides the same.
In any case, the fact that mirrors and reverse lights are on the same circuit and I noticed the mirrors not working shortly after changing bulbs may be a coincidence.

So now the real fun begins.
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Old 03-21-2019, 10:55 PM
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Billu
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If you hear the shift click, you have power to the mirror adjuster. I would be suspicious of the right/left selector switch. When mine started to fail, I only lost the passenger side, would come back by working the switch back and forth. Before I could troubleshoot, started losing both sides. I shot some contact cleaner in, things got a little better, but a new switch from Roger solved the problem permanently.
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Old 03-22-2019, 03:07 AM
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dr bob
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I would start with the basics. Fuses, relay-relay-relay if it applied, and clean the grounds.

I'd also check with your detailer to see if they removed the mirrors as part of the detailing. Or tried to. The motors are accessible by removing the mirror glass. The WSM and tips pages offer guidance on releasing the locking ring that holds the mirror glass to the motor base. Once the glass is out of the way you'll have a better look at the mirror guts to see how it might be damaged. You can do some meter testing at the motors to see if the problem is local there or in wiring/switches.
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Old 03-22-2019, 08:14 AM
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M. Requin
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I would be trying to recall whether I had used the mirror adjustment recently, i.e. before discovering the blown bulb. It's pretty easy to look at bulb>mirror as post hoc ergo propter hoc, but it's probably coincidental. And I'm with the good doctor on this, too: grounds should be a mantra all its own, like relays: grounds-grounds-grounds. And with Billu- those dinky little mirror switches (and their connections) can be problematic.
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Old 04-11-2019, 10:33 AM
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KenRudd
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Follow up:
1. While I still think it is very strange the mirror circuit and the reverse lights are on the same fuse, that was a red herring.
2. The real issue appears to be the multi-position switch in the armrest, part 91161311500. I removed it, tested for correct voltage at the White/red wire ( +12V in). I then flooded it with Deoxit. Partial functionality restored.
3. I am ordering a new switch and sealing grommet from Roger.

My theory is that when my detailer was cleaning the door rest, some Lexol or whatever cleaner he was using dripped down into that switch and gummed it up. Old grommet did not stop influx. A little Deoxit helped, but the switch is still 30+ years old, so replacement is due.
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Old 04-12-2019, 07:37 AM
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Tricky, that one! Nice work.
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