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by Duff McCutcheon

There’s one simple reason for looking after your charging and starting system. If you neglect it, your truck’s not gonna start.

So you’re driving along listening to Howard Stern and you notice the radio’s starting to pick up more static and volume’s going down. And your lights are getting progressively dimmer to boot. All are good signs that your charging system is starting to go. If you’re in a newer truck, you’ll probably be alerted to that fact via a warning light coming on. All signals point to a problem with your alternator.

If you think of your alternator as an electrical pump that keeps current going through the truck’s electrical system, and consider voltage as electrical pressure, when you reduce the amount of pressure – in the form of a faulty alternator – then your current flow is going to be reduced. “And if you don’t have the current flow, things won’t be functioning as well as they can,” says Al Willms, program head, Heavy Equipment/Truck & Transport Technician Program at the Saskatchewan Institute of Applied Science and Technology.

And it won’t just be your radio and lights suffering. If you keep driving, the engine’s bound to quit. The ECM is a computer, and it needs a certain minimum voltage. And because the charging system hasn’t been working and the batteries have been taking up the slack, you probably won’t have enough of a charge left to crank the engine over. There you sit.

Tension, Heat, & Vibration
While it’s not much help to you after the fact, the problem could be as simple as an incorrectly tensioned drive belt – either too loose or too tight. While a lot of vehicles have automatic belt tensioners to keep optimal tension, others demand periodic manual adjustment. “One guy’s idea of tight is different from another’s,” says Willms. “One person might run the belt too loose, where you’re going to have a lot of slippage. The charger won’t work properly because the alternator isn’t turning at the correct speed.”

On the other hand, the guy that tightens the belt too much is putting excess tension on the bearing that supports the rotor shaft in the alternator, Willms points out. That’s going to put a lot of side pressure on the bearing, eventually causing it to fail.

The proper way to adjust belt tension is to use a belt tension gauge – a tool that slips over top of the belt and allows the user to take a measurement between the bottom of the gauge and the top of the belt. After referring back to your service manual as to the proper belt tension, you adjust accordingly.

Vibration is another killer, perhaps from a defective alternator bracket, which should be covered under warranty, according to Willms. “Or it could be the rectifier within the alternator that’s malfunctioning, or maybe a short in the stator (the cooper winding inside the unit) – there’s any number of alternator problems that could cause voltage to drop.”

Heat, too, can cause a premature death. EGR-induced underhood heat has been recognized as a serious problem, both for belts and the innards of the alternator. Replacement alternators for recent vintage engines should have cooling vents and ports drilled into the back of the casing to improve air flow.

“With a lot of alternator problems, considering downtime costs, you should probably just replace the failed one. It’s not economically feasible to rebuild alternators anymore. You’re far better off putting on a warrantied reman unit,” says Willms.

Sussing Out Starting Systems
According to Hans Treviranus, service advisor at Brampton, Ont.’s Premier Peterbilt, the most common problems with starting systems relate to corrosion and bad connections between the alternator and battery, and battery and starter.

Corrosion happens on batteries naturally, but a good preventive maintenance program where you’re cleaning them up a couple of times a year will definitely help. Disconnect the contacts and clean the corrosion off connections with a drill-powered wire brush, add a corrosion-resistant compound and put it all back together. A little baking soda will also help neutralize any acid that might be leaking from the battery.

“Vibration can also play havoc with your batteries,” says Treviranus. “If they’re not secured properly and are allowed to bounce around, the plates inside can break up and cause the battery to discharge by itself – as well as sucking down power from other batteries.”

Regarding the starter itself, loose connections are the biggest enemy to starter performance. Because starters draw a lot of amperage, they use pretty beefy cables attached to the solenoids. Sometimes the nuts that secure these cables will work themselves loose, resulting in a bad connection.

“Every time you hit the starter there’s a bit of an arc [within the loose connection] that leaves pitting and burnt contacts. Over time the problem becomes worse and eventually the vehicle will not start,” observes Willms.

Often, it’s only a matter of tightening or cleaning the contacts. Disconnect the cables at the battery first, then disconnect the cables at the starter, clean them with a wire brush, apply a little di-electric grease to prevent corrosion, and then reconnect everything.

In some cases, the starter mounting bolts can loosen, allowing the 50-70 lb starter to tip slightly. This could make for a poor mesh between the teeth on the starter pinion and the flywheel. You’ll hear the starter turning, and maybe some grinding and clashing as the gears try – in vain – to mesh.

If you catch it soon enough, you can remedy the problem by merely tightening up the bolts. But if it’s been going for a while, then the teeth on the starter pinion will likely be damaged, as well as the teeth on the flywheel. You’ll have to replace the pinion — and make sure you replace it with one that has the same amount of teeth as the original. If you don’t you could be looking at replacing the ring gear on the flywheel.

Another problem with starters is corroded solenoids, which results in a poor connection right at the solenoid. That typically announces itself with a chattering noise as the starter tries to engage and then disengages.

“You can pick up solenoids at all parts stores and it’s not a big job to replace, provided you’ve got the starter out of the unit,” says Willms.

Of course it could be a failure in the windings or the armature. That’s not a do-it-yourself fix, so just bite the bullet and get a new starter.

Like all things electrical, the starting and charging systems will benefit greatly from a little TLC. Failing that, the problems are relatively easy to pin-point if you know what to look for. If you notice an irregularity that seems to come and go, don’t ignore it.

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