Hi Guys,

I've got a 2001 Excursion Limited 7.3 w/240K on it and for the last 4 years or so, I've been battling what seemed to be an increasing appetite for batteries - but that's not my problem, just one of the many symptoms leading up to my problem.

From time to time, my wife would go out to her car and the batteries were too weak to crank at the required minimum speed (800 rpm's I believe) to actually start. I was convinced there is/was a parasitic drain that I tried to isolate, but I've still not been able to locate or measure any drain across the NEG side on the crank battery when I put a DMM in the loop. When this happens, I simply charge the batteries and she's off and running for a few more weeks or months until the problem returns. Sometimes, but not all the times, I can also hear the "interior light relay" clicking away when the car is in this state.

Based on what I've read recently, it sounds like I must have some sort of bad ground somewhere and I'm at a loss as to how to go about finding it.

BEFORE I DO … my first question is … can a bad ground cause the engine to stall? Last night, my wife pulled her "very well warmed up car" out of the driveway after a slow start condition, and it stalled as she shifted from "reverse" to "drive". The car rolled back toward the driveway and sat there in a no-crank/no-start condition until I got home. When I looked at it, everything seemed to point to a dead battery (like I had seen before), but I was curious about the convulsing relay under the dash. I tried pulling the ground cable from the primary crank battery and with the door still open, the relay continued to rattle away. Then I pulled the negative side of the secondary battery and the relay stopped. I gave it a few minutes and then hooked everything back up. Once I did that, the relay had stopped going nuts and the car started fine - even a healthy crank rate.
This has to be a electrical issue somewhere. I glanced at the fuel bowl, but none of the electrical connections around it were clearly dangling or showing bare wire, anyone have a hunch of where I might be able to concentrate to find the culprit? Can a bad ground cause this behavior?

It's also worth saying that over time, all of our door lock actuators went out and I have not yet replaced them. In parallel to that event, the interior lights were sticking on for prolonged periods of time. I mean as much as 20 minutes while driving down the road. When I originally looked into this issue, I "thought" I had discovered the "switch" for this was actually inside of the actuator hence the reason for two electrical connections. Can anyone confirm this? I've read a post about squirting a dose of WD40 into the door lock latch until its flowing from the bottom of the door, but that sounds a bit harsh and messy. For what it's worth, the interior lights rarely (if ever) remain on any more.

 

Are you sure that the interior light relay is the one cycling? Triple check to make sure exactly which relay is the problem and swap it with another identical relay and see if the problem moves with the relay. At least you'll be 100% sure which relay is cycling and that will narrow down the circuit that needs to be trouble shot.

 

Hi lunatech,

Thank you for jumping in. I'm only certain to the extent that the relay diagram I looked at online is correct.

While I actively diagnosed the condition, I was able to isolate the relay that was clicking, and noticeably HOT, was the uppermost relay in the fuse box under the steering column to the left.

Using the owners manual, I confirmed "Relay 1" is the Interior Light Relay.





This photo was taken of my fuse box. The up arrow is meant to denote the orientation. Up is the roof/dash/windshield.

 

Have you ever spotted any water drips on the floor near the parking brake pedal? Water in that area of the dash can cause all kinds of gremlins in the electrical system.

 

Sounds like a bad voltage regulator to me. I was having some of the same issues, replaced the alternator and bingo, solved.

Although, I would look into the water leak as well.