Your cart is currently empty.
FAQ's
AlternatorOutlet.com Β· Guides & FAQ
FREQUENTLY ASKED QUESTIONS
Straight answers on high-output alternator installation, belt and pulley setup, wiring, and charging β plus the questions we get asked most. Not sure how your build should be set up? We'd rather talk it through than have you guess.
Expert Tech Support
Authorized Mechman Dealer
Get The Install Right
Belt, Pulley & Install Tips
High-output alternators pull harder on the belt drive than a stock unit. A little attention to belt tension, pulley alignment, wrap, and wiring makes the difference between a charging system that performs and one that slips or fails. Work through these before and after installation.
Higher-output alternators require more effort to spin than a lower-amperage unit when under load. That additional effort places more strain on the alternator drive belt.
If the alternator pulley is not aligned perfectly with the other pulleys on the engine, the belt will slip. Lay a straight edge across the face of the pulleys to verify the belt is aligned properly.
V-belt applications should have no more than 3/8β³ of belt deflection once the alternator is installed. Serpentine applications should use a belt length that places the spring tensioner in the center of its travel β if the tensioner is too far outside its operating range in either direction, the belt will slip.
Vehicles with poor belt βwrapβ are more prone to slip than those with good wrap around the alternator pulley. If needed, fabricate a bracket to mount an additional free-spinning idler pulley that rides on the back of the belt and forces it to wrap further around the alternator pulley.
Lower-amperage alternators won't slip the belt as badly as a higher-amperage unit, and can run a larger-diameter pulley than the same unit in a higher-amperage configuration. Larger pulleys grip better, but on some higher-amperage alternators they will not charge at idle.
170 amp S-series and 250 amp Elite-series units are the best choice for high-RPM racing applications.
- Single V-belt and 4-rib serpentine belts start to slip at about 150 amps of load. For minimal belt slip, 240β370 amp alternators should not be driven by anything narrower than a 6-rib serpentine or dual-V belt setup.
- Calculate pulley ratio by dividing your crankshaft pulley diameter by the alternator pulley diameter. Example: a 6β³ crank pulley with a 2β³ alternator pulley = a 3:1 ratio, so the alternator spins 3Γ engine RPM β 18,000 alternator RPM at 6,000 engine RPM. G-series alternators are rated to 18,000 RPM, while S- and Elite-series are rated to 20,000 RPM.
It is absolutely imperative that a properly sized positive and ground cable be run directly from the alternator to the terminals of the battery.
Improperly crimped or oversized ring terminals on your charge and ground cables can easily damage the alternator or cause a fire. The hole in the ring terminal must match the diameter of the stud or bolt exactly. An oversized hole creates a high-resistance connection that burns off amperage as heat and, in some cases, can melt off the stud.
Common Questions
Frequently Asked Questions
QWill installing a higher-amperage alternator damage my vehicle or my battery(s)?
A
No. As long as the battery(s) are in good condition and the correctly sized charge and ground cables are installed properly, nothing on the vehicle will be adversely affected.
QMy vehicle's alternator is computer controlled. Will a higher-output alternator work properly in my application?
A
Yes β as long as the alternator is installed properly. Some PCM-controlled vehicles require specific cable routing (instructions are provided). A Mechman high-output alternator will work fine and provide more amperage than the OEM unit.
QIf I install a higher-output alternator, will my charging voltage be higher than stock?
A
That depends. Most Mechman alternators are designed to operate at the OEM voltage β this is intentional, so the vehicle is not harmed by higher-than-stock charging voltage. A higher-amperage alternator keeps voltage closer to OEM when the vehicle is drawing more current from the battery. If you need higher-than-OEM charging voltage, contact a sales rep about custom ordering your alternator with adjustable voltage.
QWill a higher-amperage alternator draw more horsepower from the engine or reduce my fuel economy?
A
That depends. The more amperage an alternator makes, the more horsepower is required to turn it β but all alternators are regulated. Unless there is a heavy electrical load against it, a higher-amperage alternator won't create any more drag on the engine than the OEM alternator.
QCan a 2-pin GM regulator be used in external-regulator applications?
A
No. The GM 2-pin is ECU controlled and differs greatly from a βterminal blockβ or Mopar/Dodge-style regulator. If you need external regulation, please call or email us to discuss and set it up.
QCan you spin an alternator backwards?
A
Short answer: yes. Long answer: no. The alternator will charge spinning backwards, but efficiency drops nearly 40% because the internal fan isn't designed for it. Special rotors/fans are used in reverse-rotation applications to restore efficiency, cooling, and durability.
QMy battery is completely dead (or nothing happens when I turn the key). Will my alternator recharge it?
A
Yes and no. It will charge the battery, but this should be avoided. Alternators are made to sustain a battery's charge, not to recharge a dead or very low one. Doing so puts far too much load on the alternator and will shorten its life. Charge a dead battery with a proper battery charger first.
Quick Reference
Popular GM Truck / SUV Belt Part Numbers
Still have a question?
Tell us your vehicle, your electrical goals, and how it's set up β we'll help you dial in the right alternator, pulley, and belt so it charges the way it should.