87 4Runner

My tail light fuse blows every time I turn on the lights, so I suspect that I have a short in a wire somewhere. What's a good way to test? I have a DVOM and have checked continuity from the ground wire to the other three wires (tail light, side marker and backup light) on both sides and it comes up clean. Any other ideas?

I had the same problem, I found that the previous owner had a loose wire in the back of the truck where they had spliced in for towing plug. No protection and would pop fuse after shorting out. You have probably check any of this already but just in case I thought I would bring it up. Good luck!

Check the wires to the license plate lights too. That's part of the same loop.

When my lights blew a fuse, a knowledgable friend asks me "Did you put a new stereo in or something?" BINGO! Found the short right on top of the new radio. I'm great at makin' work for myself. Never go idle <img src="/forums/images/graemlins/rolleyes.gif" alt="" />.
How about you: Anything new, or did it "just happen:?

Yeah, I put in a stereo but it's wired into the original stereo harness and has been in for about 2 weeks now, could that cause a tail light fuse to blow? As I recall, it's the horn and radio that are on the same circuit.

I'm not clear about what you've done, but if you connect one side of your meter to a ground (battery negative is best) & probe the other 3 possibilities with the other side, only the ground should show continuity.

Dave

What I've done is use the chassis ground in the exisiting wiring harness then checked the continuity between that and the other three terminals. All three check out, so I figure I must have a problem between the switch and the fuse block....

I had problems when I tried to install a new stereo to the factory wires on my '85. No fuse popping, but I did have proeblems with some tail lights not working properly. For a quick test, unplug the stereo and see if the problem clears up. I ended up running new power wires to my stereo and it has been fine since.

Well, that settles it. I unplugged the stereo and the fuses stay good. Really strange, I wonder if the two circuits are pinched together somewhere in the harness. Anyway, I'm going to run new power wires and call it good. Thanks guys!!

I'm not sure how the 4runnas are wired from the factory but the problem with the stereo wiring maybe to do with the dimmer wire. On some factory stereos theres a wire thats live when the lights are turned on to either illuminate the knobs or dim the lights if they're too bright. ALOT of my mates have made the same mistake when wiring up stereos. On some vehicles (toyotas included I think) the illumination wire thats live when the lights are on is black or black with a dark stripe.

So people sometimes run their stereo wiring up to this black wire thinking it's an earth and all is good until you turn your lights on. Might be worth checking the earth the stereo uses <img src="/forums/images/graemlins/cheers.gif" alt="" />