Join Date: Dec 2001
Location: Belleville, Illinois
Thanked 22 Times in 17 Posts
First, testing for voltage with a digital multimeter is a dicey proposition. Typically they are so sensitive that they can pick up voltage where there's such great resistance that there's not enough power to do anything more than tickle the voltmeter. That's why you can get readings from 7 to 11.5 when there's nothing apparent to cause the fluctuation. You're generally better off to use a 12-volt test light. If there's not enough power to light the bulb you have nothing, despite what the meter might say.
Second, your problem is typical of that caused by bad grounds. My old Jeep has a connector at the driver's left foot that takes the harness to the rear along the side, behind the roll bar and to the rear of the left fenderwell. At that point it goes through a boot and to the left-side lights. The remaining cable goes from there through the back of the tub to the right lights.
At the point where the cable drops through the fenderwell is a screw into the tub that serves as a ground point for all the rear lights. If this were my Jeep, that screw would be loose or into rusted metal. Your Jeep probably has a similar ground point somewhere along the wire harness, and it's more likely inside the body than outside. And, being in the Great Salty North Country, it's probably rusty.