98 GS - Brake Light malfunction

[VaAceman]

Before I get into the specfics of my problem I wanted everyone to know I'm ware that the 3rd Brake light is tied into other systems on the car like cruise control.

Car: 98 Mit Eclipse GS

First Noticable Issue: Apprently the 3rd brake light on the car burned out and as a result I noticed that cruise control on the car no longer worked. I put in a spare bulb that I had in the car and cruise control started working, BUT I noticed that now the rear brake light (the 3rd) didn't brighten when the brakes were applied.

Problem: Back passenger side brake light (3rd) dims when brake is applied. Additionally, when the right turn signal is engaged the rear lights on the right side of the car alternately-blink, and the blinker in the dashboard HUD blinks twice as fast as a left-turn signal.

Fixs Applied: (not fixed) I purchased all new bulbs for the right-side rear of the car (part: 2057). After all were installed the problem still remains. All fuses for the entire car were pulled and examined and I can not see any corosion or fuse issues. I have alternated the WORKING bulbs from the left side of the car over to the right and the same problem remains. So the bulbs are fine.

Does anyone know what might be causing this issue? As I know it's not the bulbs, and I'm pretty sure the fuses are fine.. does anyone know where else I can look? or something I can check?

Attached is a image of the rear of the car so you can see exactly which lights I'm having issue with and what it looks like.

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[VaAceman]

Coworker says it's a ground most likely in the dash.. can anyone tell me how best to check for grounds? Other then doing a visual check

 

[luv2rallye]

I would say it's a bad/partial ground at the rear "problem light" bulb/connector. Second choice would be a faulty "turn signal and hazard flasher unit" (borrow a friend's to test). For ground testing get a multimeter and connect the negative to a sure ground (eg. bare metal frame like to the unpainted bolt holding the hatch latch mechanism). From inside the hatch remove rear light cover. Unscrew the bulb holder and with the bulb still in it, you can measure resistance (touch the other lead) on the metal side of the bulb. If it's not zero you have a ground problem. You can test all the rear bulbs this way for bad grounds.