Hi all. 2006 Explorer with a perplexing issue that I am scratching my head over. When engine revs to around 3000 RPM, there is a click that sounds like it is under the dash, and the ABS, traction control, and airbag lights come on; if the headlights are on, the dash lights around the a/c controls go out, and sometimes (but not every time) the speedometer and odometer drop to zero. Also, the overhead lighting, if on, goes out. The engine does not appear to be affected. After about 1 second, another click, and everything returns to normal. This happens either while driving or if in park and revving engine. Is this possibly a relay tripping? And if so, why is it triggered by 3000 RPMs? Thanks - Scott

 

About the only tie I can think of to engine speed would be the alternator, and possibly one or more bad diodes in the alternator causing a large amount of alternating current noise to overwhelm the battery and screw up the ECM.

Do you happen to have a scan tool with datastream mode? If so, try connecting it to see if it continues to work fine through one of these episodes. You could also use the scan tool to identify a bit more precisely what RPM triggers this, how repeatable it is, and what happens if you maintain that engine speed (does the issue continue until you change to another RPM or is it just a matter of time even if you maintain engine speed.

If you do not have a scan tool and don't want an excuse to buy one, consider checking the date on the battery and replace it if it is more than 3 or 4 years old. When replacing it, make sure the cables are clean and reconnected securely. Pay careful attention to the condition of the ground cable. If you have a multimeter, monitor the AC voltage (ACV) across the battery with the engine running. If there are more than a few millivolts of AC at the battery you might be at risk for ruining the new battery due to a faulty alternator.

-Rod

 

I suspected the alternator as well since I replaced it right at a month ago. While I don't remember this symptom before I replaced it, it's my wife's rig and I doubt she ever gets it over 2500 RPM. I just took the alternator back to where I bought it and it passed their tests, however I don't think their machine spins it fast enough to see the same issue I'm having. I don't know what else would cause what I assume is a voltage spike. The battery cables are clean, battery is about 3 years old. No datastream tool at this time to try out to get more specifics on it.