Not all battery-related problems are caused by the battery, and sometimes the battery is the last place a technician looks for a problem, when it should be the first.
Here are some examples.
1) Have you heard the one about the 1984 Honda Accord 1.8 that showed up at a technician’s door suffering from power loss any time an accessory was turned on? The battery and the alternator tested out fine, as did the ignition. It turns out that the car had a bad ground connection (located at the thermostat). A simple fix, but tough to find when you’re looking for more complex problems.
2) In another Honda issue, an unlucky tech learned to get the whole story first. A 1985 Honda Civic CRX Si was towed up to his shop. The customers said it died while driving. The battery was fully charged, but the 55 amp main fuse was blown. Trying to repeat the problem, the technician replaced the fuse and started the car with a battery load tester. At about 4,000 rpm, and registering a 50 to 60 amp load from the alternator, he was able to get the fuse to blow. (No kidding). Still, it didn’t answer the pressing question of how the alternator could do so under normal conditions. Upon further investigation the technician finds out that the customer ran the battery flat by leaving the lights on, and then jump-started it which blew the fuse. After replacing it, everything worked fine and no further problems were reported.
3) More on the import front, an Isuzu Trooper suffering from an air conditioning problem, turned out to need a charging system fix. As an intermittent problem, it was even tougher to diagnose. The details were as follows: dash warning lights come on (brake, battery) and power to the a/c blower goes out; revving the engine makes the symptoms disappear. The fix turns out to be a charging system relay. It turns out that the a/c blower will not operate when the alternator is not charging.
4) Lexus let down: 1992 Lexus ES300. This car suffered from a battery overcharging condition. With the engine off idle and any load on, the alternator was pushing 60-80 amps all the time. This condition already burned out one alternator and the replacement was looking to join it in the used fried parts bin. Likewise the battery, which was literally boiling. The problem? It turns out that one of the three wires at the regulator plug was broken. The small white wire is supposed to be “hot” all the time and, if it isn’t, the alternator thinks that the battery is dead and tries to shock it back to life. Wire fixed, problem fixed.
5) Here’s one for Sherlock Holmes. A 1995 Oldsmobile Eighty-Eight arrived at a shop with a stalling problem. A scan revealed little out of the ordinary, and the stalling problem could occur at any speed. Restart is immediate. No codes set. The technician checks all electrical connections and throttle sensors and finds no problem. He also checks the battery cables–wiggling them while checking–but finds only a 0.2v drop. Out of ideas, the customer was sent on his way. Some time later, the problem recurred more severely as the car was driven over speed bumps. As it turns out the tech should have checked the battery cables more thoroughly. It took the next garage more than three hours to determine that the battery cables were bad. As Holmes would say, “If every other possibility has been eliminated, the remaining one, no matter how improbable, must be the solution.”
6) While in the winter it may be less of a problem, a low battery can cause an air-conditioning system to malfunction. This may be part of a failsafe system on the car which prevents such large drains on the system when it perceives that the battery is on the verge of failure.
7) VW alarm going off? Maybe it’s the battery. Apparently on many late model VW cars, a low battery will cause the alarm to activate spontaneously.
8) To charge or not to charge. Late 1980s and early 1990s Honda vehicles are equipped with a timing circuit on the voltage regulator. After starting, this circuit will keep an alternator at 10 amp output for 60 seconds. Techs should wait for this to clear before testing alternator output, lest a new alternator be unfairly condemned.
9) Electrical drain problems can abound on today’s accessory-laden cars. One of the situations mentioned on several occasions was door switches corroding and creating a constant ground (not necessarily with the interior light on).
10) 1992 and 1993 Ford Explorers with the 4.0L V6 may have all the symptoms of needing a starter or a battery when it’s wiring they’re in need of. These vehicles are prone to corrosion inside the wires. Inspecting the battery cables and wiring harness in the vicinity of the battery can save everyone a lot of wasted time and effort.