Auto Service World
Feature   January 1, 2001   by Jim Anderton

break through…into 21st century alternator and starter service

Replacing a starter or alternator with a quality reman unit takes care and patience to avoid premature failures


Rotating electrical components are some of the most profitable jobs in a modern shop, and require less outright technical knowledge than ECM or fuel injection technology. Why then, do so many good reman units end up as fried cores and warranty claims? The answer usually has more to do with diagnosis and service procedures than quality issues with name-brand alternators and starters. Avoiding comebacks on alternators and starters begins with diagnosis and careful installation.

Why they fail

Remanufactured or new, the root causes of alternator and starter failure have something in common: they’re susceptible because they’re both electrical and mechanical devices. That means trouble can start in several places within the unit. Dick Martin, National Service and Training Manager for ACDelco explains: “Starters have commutators, brushes, bearings and bushings, and those are the things that usually take the abuse, based on start time and the number of starts. Today’s engines are a lot less abusive to a cranking motor because of the quick starts from fuel injection.” Martin cites other factors such as general engine condition and temperature as contributors to decreased starter life: ” It’s a combination of several things. Drives (may fail) based on shock loading of the engine. Today, cranking motor life is a lot longer. Average crank time is down compared to the days of carburetors. The other thing that kills cranking motors is low battery voltage. Higher heat damages the electrical components.” Heat is also a killer to alternators, declares Martin: “It’s because of the higher electrical loads. Alternators are smaller, with higher output, so there’s more heat. The thing that kills them is incorrect belt loading, and continuous high electrical loads, depending on the drive cycle. A lot of city driving, low speeds, and (poor) battery condition generates heat. They can have electrical failures because of high loads as well as their normal life cycles based on engine RPM and belt loading.”

Wiring is still the most overlooked part of starter and alternator diagnostics, and wiring can cause trouble far away from the either unit. Bad engine ground straps or cables, for example, can reduce the amount of holding current fed to a starter solenoid, causing it to drop out during cranking. The same ground issue can reduce starter RPM’s causing longer cranking time and further heat buildup. Intermittents in the ignition switch are worth considering, as is the possibility of a fried unit from missing heat shielding. Even new battery terminals are a possible source of trouble if the original crimped cables were replaced with clamp-on emergency terminals. The clamp design of emergency terminals limits the contact area between post and cable strands, effectively downgauging the cable size. Correct cables can sometimes cure a lazy starter, and will definitely help preserve a new unit.

Alternators are durable, yet sensitive

Alternator technology has advanced considerably since the externally regulated units of the “points and condenser” era; it has had to, mainly because of dramatic increases in total electrical loads in modern vehicles. One change which has improved durability is the shift to load sensitive regulation. The new regulator designs ramp up current gradually to avoid shock loading the drive belt and the alternator’s front bearing assembly. Shock loading is a serious issue, since intermittent load accessories such as power steering pumps and A/C compressors transmit their loads directly to the alternator through modern serpentine belts. The belts aren’t themselves a cause of premature failure, but the heat generated by slipping belts can be, both as a result of slippage between alternator pulley grooves and the belt ribbing, and through the belt back side where it contacts the idler. The frictional heat resulting from the slippage is transmitted through the pulley and into the alternator front bearing assembly, where it can build up to the point where the bearing lube flows, with inevitable consequences. The solution is to check tensioned assemblies and pulley alignment before removing the unit.

Dissipation of heat has always been important to full alternator life, but transverse engines, electric cooling fans and ever-smaller grille openings have contributed to much higher underhood temperatures than in the days of the “Delcotron”. Dedicated ducting or deflector vanes are essential, and in many cases, under car air dams contribute airflow on which vehicle designers rely for alternator cooling. A good diagnostic procedure would include a check for missing ducts, vanes, or under car aero aids. A customer could, for example, peel off an air dam on a parking lot curb and not realize that alternator damage can result. If the missing air flow components are the result of another tech’s work (or a DIY’er) then the shop manual may be the only way to know what the OEM installed at the factory. If they installed it, it’s necessary.

Battery testing is essential

Batteries, specifically weak or damaged units, are also potential alternator killers. The most common scenario is the “death by overwork” condition caused by alternators that must continually deliver more than their rated current output in an attempt to keep the cells charged. “People think that alternators are chargers, but they’re not,” declares

Patrick Ttreault, customer service supervisor for Dynamic Automotive: “They supply the current that you need for all your accessories. It only works at 70 percent of its capacity, so if the alternator is 100 amps, it only works at 70 amps (continuous) to give you the current everywhere and stabilize the battery, not charge it. If they made a battery charger cheap, they would put an alternator in there. But there’s not. A charger is 800 or 900 dollars. And you have to charge it for hours, not just five minutes.” Tetreault also notes that the A/C compressor can contribute to shortened alternator life through its compressor clutch. When the unit is de-energized, the collapsing magnetic field in the clutch’s windings induces a current or “back EMF” just like the ignition coil. This potentially damaging current is bled to ground by a small diode, often wrapped in tape inside the line feeding the compressor clutch. Testing this diode is quick, and helps to minimize comebacks, especially where the clutch is cycling frequently. Another tip is to ask the customer if he or she revs the engine during shutdown. Although this practice used to be common to clean “cold” plugs in high-performance engines, it’s not only unnecessary, but can create damaging current during the “wind down” of the engine.

One test that used to be a staple of charging system diagnosis was full-fielding the alternator to isolate regulator failures. Regulators were then replaced as a bench repair, and the unit reinstalled. Although quality reman product has largely removed the need for full-field testing, some technicians use it as a quick confirmation of alternator failure. Many modern alternators, however, would need in-line resistances to safely field the unit. Unless you’re curious and are servicing a unit such as the Delco 10SI or 12SI, (which provides for a brief screwdriver-grounding), stick with conventional load testing and diagnostic procedures.

Choosing a replacement

Once the diagnosis has been made and the original problem corrected, it’s time to select a replacement unit. Pricing varies, and if the job needs to come in at a low price, be wary of deals that seem too good to be true. There is a difference between “rebuilt” and “remanufactured”, says Cameron Young, marketing manager for Bosch. “From a remanufacturing standpoint, it’s replacing as much componentry with new as possible. Rebuilding is more reusing and recleaning of existing parts.” Performance of remanufactured units is at least as high as newman, according to Young: “In some cases it’s higher. We offer a twelve month warranty.” Young also notes that installers often overlook extended warranties and roadside assistance plans: “He’s go
t to present it to the end user. Bosch offers a 24 month roadside assistance program which protects both installer and consumer, but only if installers inform the customer and either encourage them to fill in the form, or fill it in for them. Unfortunately, in some cases we see cores coming back with (warranty tags) still in the boxes. I highly recommend that installers work with consumers on this, because it takes the installer’s hands off the potential liability for a tow or a boost.”

To generate good income and customer satisfaction in rotating electrical component service, the customer has to be convinced of the need to pay for adequate diagnosis, especially if there’s a warranty claim. Dick Martin says: “On a second failure, do some analysis. Don’t just blame the component. It could be a missing duct, an incorrect belt tensioner, or a bad fan clutch.” Patrick Ttreault agrees: “Damage is the result of what originally happened. Changing the starter or alternator is not giving you the answer. Check wiring, fuse boxes, fusible links and diodes. It’s costing everybody money.

Garages are scared to charge for it. A good test for a starter and alternator takes around 15 to 20 minutes. Charge an hour and do a really good test: voltage, amps, and negative voltage.” Does it pay? One remanufacturer told SSGM that 55 percent of returned cores are good units. Each one of those needless replacements was an opportunity to perform a good diagnosis, and to prove to the customer how it saves them money by avoiding needless replacements. And besides, if the unit wore prematurely, or wasn’t bad in the first place, both customer and technician still have a problem. Take the time for serious diagnosis, install quality parts, and the chances of a comeback become very, very remote. SSGM