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Auto Q&A: Dimming Dash Lights
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Posted by editor Tue Dec 26, 2006 12:59:44 PST
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0 responses 0 comments Dear Q & A: I’ve got a 1993 GMC pickup and my problem is this. My dash lights have been getting dimmer lately and the battery gauge on the dash shows my battery level very far down to the left. I had the battery charged at a friend’s house (he has a charger), and that seemed to cure it for a while, but the same thing is happening again. Should I just go ahead and buy a new battery, like my friend says, or what? I’m handy enough to replace it myself. Any suggestions?         - Cory

Dear Cory: That “battery gauge” is a voltmeter. It doesn’t show “battery level” but the rate at which your truck’s alternator (some still call it a “generator”) is charging the battery, that is, replenishing the electricity being depleted by starter, engine, lights, radio, and other electrical accessories as you drive.

Your symptoms indicate you may have a defective alternator. If you’re handy, you can even replace your alternator yourself. But before you pop for an one, make sure your battery isn’t defective and is fully charged. The alternator is that cantaloupe-size device mounted high above and in front of your engine and driven by the serpentine belt that also drives the power steering and air conditioner. It’s easy to reach in your truck, the trickiest part maybe being releasing the tension on your belt and replacing the belt properly after you’ve bolted in the new alternator.

Many auto parts stores are likely to have your alternator in stock — it’s a popular model — at prices between $100 and $175, depending on quality and warranty period. If you decide to do it yourself, here’s a rough idea of what to expect (but follow the specific instructions that accompany your particular model).

First disconnect the negative (-) battery cable and lay it aside so it can’t contact the battery post. Next, using a socket wrench (probably a 16 mm socket) with a long handle (a 12-inch length of pipe will extend it), release the tension on the belt and remove it from the pulley on the old alternator. Then carefully remove the wires bolted and clipped to the back and side of the alternator. Now unscrew and remove the three bolts holding the alternator in place, and pull it up and out of its mounting brackets. Compare the old with the new alternator to make sure they match: pulley, size, shape, and mounting points.

Clean the mounting brackets so the new alternator has a good ground connection. Slide the new alt. into place and reinstall the mounting bolts. Using the same long-handled wrench, release the tension on the automatic tensioner enough to replace the belt in position on the new alternator pulley. Note: If your belt has over 50,000 miles on it or is cracked or otherwise defective, now’s the time to replace it. Make sure the entire belt is in proper alignment, routing, and position over all the pulleys of its travel.

Reconnect the wires to the new alternator. Finally, replace the cable onto the negative post of the battery. Double-check the mounting bolts, belt routing and tension, wiring, and battery cable.

Now start your engine. Your voltmeter should now show a charging rate in the vicinity of 13.5 to 15 volts. If it’s not within this range, better see your mechanic, who can determine whether the new alt. may be defective (rare) or you may have a more elusive problem. Some replacement alternators come with a phone number at which you can get installation advice.

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