Backup Lights Fuse Blows???

rabidscoobie

10 Year Member
Jun 21, 2007
595
7
48
College Station,TX
Everytime I put it into reverse my fuse for the backup lights blows and soon as the shifter goes into reverse,it is the only time it blows.

I even disconnected both tail light housing and harness from car itself, same result. Only noticed this today.

Also first week of june up until 3rd week of july I had the car basically torn apart body wise.
Trunk,all lights,bumpers,fenders and various other parts off since I was stripping it down to bare metal and repainting it.
I know for a fact they worked without blowing fuse the day I started taking it apart.

I dont think anything is wrong with wiring since the only wires that were messed with during tear down was removing the trunk.

I was thinking it is a bad backup light switch?, Thoughts...ideas?

Also CCRM was replaced last November, all new bulbs put in all way round. Replaced all interior,cluster lighting with LED, outside are original style bulbs, no LED's on the outside.
Added floor courtesy LED's since Im sick of not seeing the floor at night, but only tapped into the wire for the door that makes the dome light come on. Tapped into the wire that runs up the passenger side A-pillar. Checked there, no wiring issues. Everything was soldered and heat shrink, no tape used.

So I dont think any of that is causing the issue.


And just to show off completed car, well at the time of pic. Since have done smoked tails and a couple other things. I did every bit of work on the body and paint. Took me 2 months to finish counting wet sand, buff and polish. Also those headlights were wet sanded down and sprayed with 2k clear, look like new again.
Not too bad for a first full paint job in the backyard, at least I dont think so.

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wmburns

SN Certified Technician
Aug 14, 2009
5,360
417
164
Houston Texas
I dont think anything is wrong with wiring since the only wires that were messed with during tear down was removing the trunk.

I was thinking it is a bad backup light switch?, Thoughts...ideas?
IF you are positive there isn't a wiring problem THEN the most likely problem location would be the switch itself.

How to test. Use a test light on battery positive. Disconnect the reverse light switch. Probe each terminal of the back up light switch. The test light should NOT light. Now put it into reverse and repeat the test. Does the test light light? If so, this "proves" there's a ground fault inside the switch.
 

rabidscoobie

10 Year Member
Jun 21, 2007
595
7
48
College Station,TX
IF you are positive there isn't a wiring problem THEN the most likely problem location would be the switch itself.

How to test. Use a test light on battery positive. Disconnect the reverse light switch. Probe each terminal of the back up light switch. The test light should NOT light. Now put it into reverse and repeat the test. Does the test light light? If so, this "proves" there's a ground fault inside the switch.
Thanks.
I will give that test a go this evening or in the morning, too hot right now.

Thanks for telling me how, i hate automotive electronics.
Its a very weak area for me...lol.

As far as when doing tear down i never touched any wiring except removing all lights and the antenna wire. I went through all those lights and checked the plugs and harness in those general areas and all still looked good.

I even looked under dash for any chaffing or bare wires and where the harness goes thru firewall, everything was good there also.
I also disconnected all wires to car alarm brain to check if that was causing any issues since installed it 10 or so years ago, also wasnt the problem.
 

rabidscoobie

10 Year Member
Jun 21, 2007
595
7
48
College Station,TX
Thanks for that info, got some shade so I did the test.

Assuming I chose the correct pigtail rom the trans, mid way down housing on driver side.
Disconnected 2 wire plug from switch, put in neutral. No light on test light coming out of switch.
Same test but in Reverse, probe lit up out of switch.

So bad switch then.

Thanks, like I said I may finally figured it out on my own but your help made it much easier and quicker. I am terrible at auto electrical.