I've read about this symptom in several archived threads, but I can't respond to those because they are archived. I wanted to document my solution with photos, so here goes:

My symptoms were:
- When only the turn signals were on, everything was fine. When turn signals and brakes on at the same time, then the turn signals stopped flashing and everything stayed dimly lit.
- With the car totally off, if I hit the brakes, the chime would go off.

The culprit was a bad G400 ground point. This ground is located right at the top of the passenger, rear wheel well.



Ya, this is what mine looked like after I wrenched on it ever so slightly:


I was able to get it apart, bolt it to another bolt in the area, and everything worked normal again. However, I now realize I have some major rust cancer going in that wheel well and trunk area. Looks like I'll have to decide how to fix the rust.

Thanks!

..

[This message has been edited by tshark (edited 09-08-2018).]

Guess you didn't look in my cave?
Sneak Path
While covers only 1 rear socket w/ bad ground, problems w/ more sockets or G400 G10x are common.

For a quick test... use a pin to pierce the ground anywhere that's easy then jump pin to frame. That works w/o pulling inner fender etc.
If that helps or not... Pull the pin then wipe the hole w/ silicon oil or grease to keep out water. (Wire Plastic should heal the hole but many leak water in.)

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

Thanks for posting the pic of the location, I bet many people don't know that ground is there.

Yeah inspect your car for structural stability, that's serious rust.

I'm sorry to say that a bad electrical ground is the least of your problems with that poor Fiero.

This fella had the same unfortunate issue...

That is a lot of rust sadly.