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Click, Click, Click...Posted 12/13/2000By Brian Manley
You've had your morning coffee, so now you grab your coat, slide on your gloves and head out to the lot with a set of keys to Mr. DOA's car. You unlock the driver's door and break open the below-freezing barrier, then you brush off the pile of snow that always gets sucked onto the seat. The cold vinyl cracks under your weight as you insert the ignition key. Click, click, click. No starter reaction. Now, what steps will you take to get this car from “Dead On Arrival” status to a reliable, starting, charging grocery getter? For this month's Tech to Tech column, I will throw out the procedure that I would use on Mr. DOA's car. Then, and this is the important part, I want YOU to e-mail me with your feedback. Did I miss a step? Or mention one that you consider irrelevant? My goal is to combine all of the good information out there with your thousands of years of combined tech experience and roll it all into a comprehensive flow chart. This chart can then be used as a tool for selling service and a checklist so that none of us forget a step while thinking about lunch, or the anniversary gift that we forgot to get. Due to length, we will address only battery troubleshooting, charging system analysis and diagnosing parasitic drains. The Interview Questioning the customer is the first, most important step. Some shops will even fax a questionnaire to the customer before the repair appointment to give them time to be thorough. Ask:
Mr. DOA's interview reveals nothing significant. He says that it “just happened last night.” Service Bulletins This is a necessary step, even for starting/charging system diagnosis. I randomly looked up a 1990 Ford Tempo on my information system and found a bulletin for a no-charge caused by a melted generator connector (we've all seen this). This bulletin rightly explained that failure to replace this melted connector could lead to a failure of the new generator, due to high resistance. Another bulletin profiled sticking fuel pump relays, which can cause a huge parasitic drain and a very dead battery. Seizing the opportunity to look up these bulletins for your customer will help ensure a fixed-right-the-first-time car and certainly creates a service opportunity for your repair facility. A win-win situation! OK, Mr. DOA's car is a 1990 Ford Tempo. The Visual Inspection After pushing the car into your stall, you pop the hood and look for the following - in addition to the above two bulletins:
At this point it's common to see corrosion, low battery level, undersized batteries, missing hold-downs, loose/cracked alternator belts, starters covered with engine oil and dead pigeons wedged in the air intake. No, wait, that last one is an engine performance issue. Intrusive Testing Up to this point, you haven't actually taken out any tools, except your flashlight, so what is the next step? I would remove the dead battery and replace it with a known good one, then attempt a start. Why not just hook up a charger, turn it to “JUMP START” and let the electrons fly? First, if the engine starts, you run the risk of overheating the alternator if it runs at full capacity for too long. Next, if the vehicle starts, then you will perform a charging system test, starting system test, and check for a parasitic drain; you'll need a fully charged battery to properly perform these tests. If the engine still won't crank, then you will need your test light or DVOM to trace down the open circuit. Battery Testing Regardless of why the battery is in a low state of charge, it must be properly evaluated, serviced, charged and load-tested. Mr. DOA's battery has no cracks or bulges and is a sealed battery, so you check open circuit voltage with your DVOM. It reads 7.4 volts. You hook up the charger set on low and let it charge for several hours, while proceeding with the on-car tests. Engine Starts with Good Battery At this point, my first instinct is to look for any lights that have been left on: glove box, parking, trunk, map, etc. I also look for aftermarket items that may be wired to B+ at all times, instead of switched power. You don't see anything on in Mr. DOA's car, so you move on. Charging System Testing I would follow the manufacturer's procedure for this test, and I'd definitely remember to voltage drop the working generator. I strongly suggest referring to the August through October (2000) AutoInc. Tech to Tech columns for Vince Fischelli's articles on how to test the charging system. He explains that current follows voltage and illustrates how to test the system by observing voltage, rather than sizzling the generator with the carbon-pile load tester. I regard him as the guru in this arena. Mr. DOA's generator is working as it should, and voltage drops are within specs. Parasitic Drains This test should be done using a battery disconnect tool that will adapt to side-post as well as top-post batteries. After installing the test tool, road test the vehicle and use all of the accessories. This will work any potential parasite through its paces. Pull your vehicle in, shut all doors, turn off all accessories and remove the ignition key. Next, hook your ammeter (set to the 10 mamp scale) across the test switch. Open the switch while observing the amperage reading. Scale the meter down to read the lowest possible measurement. A 1997 Dodge Stratus that I tested recently had .140 amps initially; but after one minute, it dropped to .060; then, after 20 more seconds, it rested at .030 amps (30 milliamps). Different vehicles have different limits. A Honda Civic, for example, allows only .015 to .020 amps. One rule of thumb is that .050 amps is the maximum that you want to see after a 30-minute “powering down” period. If the parasitic drain exceeds limits, you will have to pull one fuse at a time until the drain disappears. Refer to a wiring diagram to see what circuits are powered by that fuse, then reinstall that fuse and start disconnecting components until the drain goes away. If pulling fuses doesn't do the trick, you'll need to move on to devices that aren't fused, such as the B+ wire at the alternator. If you pull this wire and the drain disappears, it's time for a new unit. Do the same for the B+ starter solenoid wire. Also, check for any partial shorts from the battery to the under hood accessory/relay box. You perform the above test on Mr. DOA's car and find .040 amps after two minutes - well within specs. Mr. DOA's Car You've load tested the battery and it passes, so why was this car “Dead On Arrival”? You find no other reasons for a dead battery, so you keep it overnight, just to make sure, and it fires right up the next morning. You reluctantly give it back to the customer with a caveat: “You may have an intermittent battery drain.” The vehicle shows up on a tow truck one week later. The same tests reveal nothing. What is up? Out of frustration, you decide to take a few days off to ride around with this guy to see if you can catch the car or the customer doing something weird. Finally, on the third day, you pull into Mr. DOA's driveway after a round of golf. He mumbles something about how "it looks like rain." You watch curiously as he opens his trunk and pulls out a tarp and four bungee cords, and throws the tarp over the car. He then stretches one bungee cord down, hooks it under the driver's door handle, then does the same to the passenger door handle. Voila! Your sleepless nights are over! “Didn't the customer see those interior lights come on when he does that?” you mumble to yourself as you resist the urge to show Mr. DOA how truly frustrated you are. The above “intermittent battery drain” is a true story told to me by the manager of a local dealership training center. The training center manager himself went out with the customer for four days until the day it began to rain. This illustrates the importance
of a thorough interview of the primary driver of the vehicle. It also reminds us that, as RoseAnne RoseAnnaDanna said, “It's always something!”
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Copyright (c) 1996-2008. Automotive Service Association. All rights reserved.
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