Cavalier's flashing lights could be the alternator

  • Article by: PAUL BRAND
  • Updated: June 10, 2011 - 4:15 PM

Q My daughter asked me why all the lights -- headlights, tail lights and dash lights -- pulsate at about two pulses per second on her 1997 Cavalier. Sometimes it's very noticeable, other times not so much. About the only time they don't pulsate is when it's at a stop with the foot on the brake. She jokingly worries that the pulsating lights might throw her or oncoming traffic into a panic, causing a crash. Or that the lights will just stop working, which also could end up causing a crash. OK, that's not likely, but you have to admit the pulsating headlights at night are a little scary. Any thoughts on how to fix this?

A Anytime you're dealing with an electrical issue with an older vehicle, start by physically checking wiring, connections and grounds. Then, use an analog (needle) voltmeter across the battery terminals with the engine running and the headlights on. Do you see a voltage fluctuation with each pulse? If so, check the drive belt and tensioner for proper alignment, tension and condition along with the control wire and battery connections on the alternator. And confirm there's a solid ground between engine and chassis. Make sure the battery is good -- above about 12.4 volts after sitting overnight. If it's not one of these issues, the alternator is the likely culprit.

Q I have a 2002 Chevy Suburban C2500 with the 8.1-liter V8 engine, Alison five-speed transmission and 190,000 miles. The other day, as I was driving, it just lost power and stalled. It started right back up, but now it does this every few blocks to every few miles at any speed. No check-engine lights, and my scan tool shows all is fine. Also, after about 15 minutes of driving, the cruise will also not set or function. In the driveway, I can run it up from idle to 2,500 rpm all day long with no problems. Any ideas?

A Intermittent loss of power under load with no fault codes points logically to fuel pressure. A tired fuel pump, restricted filter, bad relay or corroded wiring might be causing fuel pressure to drop below the 55 to 62 psi necessary for the engine to run. Even if fuel pressure is within the normal range while the vehicle is stationary and running, you need to mount a fuel pressure test gauge so that fuel pressure can be monitored while driving under load.

Could the problem be electrical or ignition? Do the instruments and tachometer drop instantly as the engine dies -- as if you turned the switch off? If so, the battery, terminals, connections and grounds along with the ignition switch itself are possible culprits. If the gauges continue to read as the engine dies, focus on fuel pressure.

Q My 2009 Ford Escape XLT has had a slight vibration felt in the gas pedal since the day I bought it. Every time I start the car and accelerate, the vibration is felt for just a second, very shortly after I start moving. Lately I've been feeling this vibration a second time, 10 to 20 minutes later. The second vibration doesn't happen all the time, but it seems stronger than the first and there is sometimes a slight grinding noise with it. The garage mechanics cannot feel this vibration. Any thoughts on this problem would be greatly appreciated.

A My Alldata database pulled up two service bulletins that might help. Bulletin 09-6-2, dated April 2009, suggests updating the powertrain control module (PCM) to the latest specs and performing a "powertrain neutralization procedure." Bulletin 10-20-1, dated October 2010, identifies "a single hoot noise on light acceleration from a stop before the first shift" as potentially a normal characteristic, but does identify a revised transaxle drive chain to reduce this noise. Installing the new chain requires removal and disassembly of the transaxle, so check your warranty carefully.

Motoring note

Even non-car people turn heads at the sight and sound of a beautifully restored or customized motor vehicle. And there will be lots of head-turning this week leading up to the Minnesota Street Rod Association's 38th annual "Back to the Fifties" automotive celebration at the Minnesota State Fairgrounds, starting Friday, June 17, and running through the weekend. The scale of this event is impressive -- 11,000-plus street rods, customs, classics, restored and antique cars and trucks, plus the Mecum Hot Rod Auction, outdoor concerts, swap meet, O'Reilly Manufacturer's Midway and the Ladies Showcase and Cruise-N-Craft Fair.

Spectators and exhibitors who've been to "Back to the Fifties" come back year after year. For folks who haven't walked the fairgrounds streets to classic music and custom cars, here's my personal invitation -- don't miss it!

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