I have '97 4runner. Auto, bone stock, no aftermarket stereos, lights, just stock. The battery keeps going dead over night. So, I'm figuring parasitic draw somewhere. What I've discovered has 3 pretty darn good mechanics, with probably close to 75 years of experience, baffled. When I remove the negative cable from the negative post and put a test light between negative post and negative cable, the test light flashes on and off like a turn signal is on. I removed the turn signal fuse, still flashes. Flashes full bright btw. I don't hear a clicking like the turn signal relay is clicking, but at my age, the old hearing isn't the best.

Any ideas on what I should do next? I'd sure appreciate your help.

And thanks in advance.

Just go through all the fuses, pulling each one in turn until the light goes out. Then you know what fuse circuit the issue is on. When you find that out, post back if you need tips on what to do after that. If a fuse has no power with key off, you can skip it. Makes the job a lot faster as you can test for power with your test light with the fuse in place. Try the HORN fuse first. Just a wild guess. The TURN circuit is not live with key off, but the HORN fuse is and supplies the HAZARD circuit (same flasher).

Do you have an aftermarket alarm or towing package? Or anything aftermarket, for that matter?

I'm curious to know what does this, so please post back. My dog will thank you.

Try testing for a parasitic draw with a DVM:
Diagnosing A Car Battery That Runs Down

May be a bad cable, check your grounds first:
Voltage Drop Testing