taillights energize brakelights

[jonb96150]

I've searched and checked wiring harness at rear quarterpanels as suggested to no avail.

Symptoms: Taillights will energize both filaments of the bulb resulting in constant brakelights whenever taillights are turned on.
When driving in rain turn signals come on solid with taillights until dry.

Pull the brake fuse and it still happens. But no b.l. without t.l.
Checked continuity of ground side of all rear bulb sockets to chassis, all good.

But.... There is also continuity from the center pins of the sockets to chassis. Are the center pins supposed to be grounded when the bulb is removed?

TIA for any insight. I've spent several hours on this and am clueless.

 

[Radd Cruisers]

Use Toyota bulbs ONLY.

Check your grounds and connectors in the rear of the vehicle - where the tools and jack are. Check the run that goes to the other side.

If you have trailer wiring - that is almost certainly where the problem lies.


~John

 

[jonb96150]

Thanks for the reply.

I have checked the ground underneath the left rear quaterpanel and it looks good. And I even removed this ground and the symptoms did not change at all. And when I check for ground on the ground side of the bulb socket, it tests good as well.

There is no trailer wiring. The bulbs are "Koito". I don't know if those are Toyota bulbs, but they are much heavier duty than the 24v Osram spares I picked up. The filaments are supported in the middle of their span by another post. The Osram filaments have no center support for their span. (If that makes any sense).

As far as the center pin of the socket testing to ground with the bulb removed, my neighbors 87 4Runner tests out the same. That is to say, with the bulb removed and a tester on the center (positive) pin and the other end of the tester on the chassis there is continuity with the lights turned off.

And that is where I get lost. IIRC, most N.American cars would not have continuity between the positive side of the socket and the chassis when the bulb is removed, and the lights are not turned on. But they are grounded locally to the bulb, and don't have a dedicated ground wire running back through the harness to god knows where.

I am definitely lost in space here lol!