Q:I own a 1996 Ford Contour SE with 2.5-liter V-6, manual transmission. For the last couple of years, the lights on the car blink (pulse) with increased RPM. They do not pulse at idle. Prior to an alternator replacement in June, it would only blink at initial engine startup. After the alternator replacement, it does it all the time. Right after the replacement (the alternator lasted only 15 months - they say because a mouse had built a nest in the alternator), the lights did not blink for a couple of days, then came back. I returned the car to the repair shop, they ran diagnostics and could not see any spikes in the output of the alternator or anything wrong with the battery. Later, I used my multimeter and hooked it up to a terminal on the headlights and to the battery and can see movement on the meter (it is a cheap analog meter). The battery seems to be charging fine. So I am wondering if the voltage is spiking above 12 volts. Is this a problem, besides being annoying? Any idea what is causing this? Is there an external voltage regulator I can purchase to curb the spike in voltage, if that's what it is? - David K., Coon Rapids
A:Erratic light behavior sometimes comes from a grounding problem, that is, a loose ground wire or a poor ground on corroded metal. Check your battery ground and ensure that the cable is solid and that it has a good connection at the battery and the chassis. Problems elsewhere in the wiring could also be causing or contributing to the problem.
The wiring harnesses on the '95-'97 Contour had a problem with deterioration from high heat and humidity. Given our state's extreme range of both over the course of a year, your vehicle is certainly susceptible to this problem. The wiring degradation may be identified by brittle insulation, continuous cracks in the insulation, cracks of random orientation or missing portions of insulation. This was a warranty repair for affected vehicles.
Given the number of wires carrying current, and their proximity to one another, it stands to reason that insulation damage could produce electrical interference that might manifest in something like flickering of the lights - lights being uniquely well suited to reveal current changes because their brightness will vary accordingly. If your vehicle did not receive replacements of the affected wiring harnesses, this is worth checking out. In bright sunlight or using a good shop light, take a close look at your underhood wiring and see if you see any damage or degradation to the insulation. Look for the symptoms described in the previous paragraph.
You should also take a look at Technical Service Bulletin 00-25-6 from 12/11/2000, "Charging System - Int./Ext. Lamps Flicker When Cold." While this bulletin was written for the 1999 and 2000 Mercury Cougar, it applies to the 2.5 liter V-6 engine, which will have many components in common across the Ford/Mercury line and across a number of model years. The issue the bulletin identifies is, "Some vehicles equipped with a V-6 engine may exhibit a flickering condition of the headlamps, instrument cluster, radio and interior lights during engine start-up [that] may continue during the first several minutes of engine idle." The flickering usually subsides after several minutes but may not disappear. "This may be caused by excessive electrical resistance in the battery voltage sensing circuit. Vehicle operation is not affected by this condition."
This sounds like what you were experiencing before your alternator swap. The TSB provides detailed instructions for moving the battery sensing line to correct the problem. It may also give your mechanic additional troubleshooting ideas. If anyone else writes in on this topic with suggestions or discoveries from their own experiences, I'll pass along the information.
