Blowing "Gauge" fuse while in reverse- Solved!

Figured I would post up as it may help others some day.

Driving home from work today I noticed no gauges in my instrument cluster were working (speedo, tach, odometer, etc). Blower fan was also not working. Checked the 10 amp "Gauge" fuse when I got home and it was blown. Replaced fuse, started it up, all was ok. Go park my truck in my usual spot and noticed gauges weren't working again. A couple fuses later and I finally figured out it was only blowing the fuse when I would put the truck into reverse (manual trans FWIW).

SO I knew something in the backup circuit was shorting. I checked the back up light switch located on the passenger side of the transmission to see if any wires were broken. None. Now I had replaced this switch a few times due to failure so just for giggles I tested the continuity with a ohm meter to be sure it was working as it should. Seemed ok. I was starting to dread the fact that I would have to trace the wires all the way to the tail lights to locate a short. At this point the switch is still out of the transmission but plugged in to the connector. I cleaned the ball bearing at the end of the switch and gave it a few pushes like I always do before putting it back into place. Wait a minute... for whatever reason I noticed that my gauge lights were still on after doing this, the fuse had not blown. No one else was home so I set up my cell phone video camera behind the truck just to see if the reverse lights were coming on when I would push the switch by hand. Sure enough they were. That meant no short in the wiring! I put the ohm meter back on the switch and found out that when the switch was pressed in, not only was I getting continuity between the 2 terminals, but if I put 1 prong of the ohm meter on the steel body of the switch and the other prong on either terminal I was getting continuity as well. The switch was shorting itself out!

Just as extra confirmation, I took out the 4wd switch (same as backup light switch) and put it in for the backup lights and everything worked as it should. Like I said, I've had back up switches fail before, but they would just stop working. This was a first.

I did a quick Google search before posting this and seen a few threads where people had similar problems. The threads would lead to people telling them to trace the wiring and than the OP would never return with a resolution. As rare as this issue may be, this post may help someone who would otherwise not think of the switch as being the problem.

Cliff notes:

-Blowing 10amp "gauge fuse" when truck is in reverse.
-Diagnosed the problem as faulty back up light switch. Power being shorted threw switch body.

 

Noted.
Thanks

 

i just had this happen to me today . same deal like you i had already changed the switch already...its been a while since your post whats the update?

 

No problems since.

 

Thanks for taking the effort to post this up Ktaco. I'm looking at the same symptoms and was dreading the witch hunt ahead. Maybe this does it. Fingers crossed!

 

Are you or were you using a Toyota or aftermarket switch?

 

I bought an Echlin switch at NAPA....... not fixed. I'm not surprised. I pulled the switch last night and fiddled with it using my voltmeter and nothing seemed amiss. I suspect one of my CRAP LED bulbs may be the culprit now. If this rain will cease, perhaps I'll find out.
I replace fuse, start truck, all's well...put in reverse, 1 second later, fuse blown.

 

Im having same issue, its reason i joined this site, will be checking tomorrow to see if this fix works. thanks

 

Mine indeed was a malfuncted LED bulb. Shorted internally.

 

Thank you for the advice. I have gone thru so many 10 amp fuses. I am going to try your fix tomorrow. Thanks again.

 

I hope this does it for ya. Make sure to let us know

 

I assumed this was the issue, but had not tested it yet. Thank you for saving me time in my diagnosis!

 

I had the very same problem as Ktaco - fuse would keep blow when putting into reverse. Like he, I had just replaced my back-up light switch the year before. But after reading his post, I took it out to inspect it and found that tranny fluid had fouled the switch and made it out to the plug contacts. I got the new switch, cleaned out the contacts with Q-tips, toothpicks and toilet paper, replaced it all & now it works fine. It took 18 years for the 1st switch to go, less than 1 for the aftermarket - I went the cheap route again thinking it was an anomaly, but will go for the more expensive switch if it ever happens again. Thanks Ktaco!

 

Had same issue start on me yesterday I was worried at first because I tapped into this circuit for a reverse camera and additional reverse lights but realized that they had been working fine for many weeks up until this point, sure enough it was the switch. Great post much appreciated.

 

Same issue here. Blown 10A guse. Speedometer does not work. No AC. It turned out to be a flaky (not blown) halogen reverse light bulb. Unlike many members here, I replaced it with LED bulbs on both sides. Problem remains fixed a few years later.

 

My exact issue. It's Feb 2023, on my wonderful 1998 SR5, manual, 195K. Replaced switch (probably China product) about 4 or 5 years ago to fix 'no backup lights' issue. Hope the new switch corrects my instrument failure. Great post from OP, thank you.

Update 02/14/2023: replaced switch with OEM. Perfect!! Problem solved, and a big THANK YOU to Ktaco.