12V 90A Alternator 3701020A-E01 for pickup

Overview of the 3701020A-E01 Alternator

The 3701020A-E01 is a 12V, 90A alternator for pickup. It is a claw-pole machine with an integrated regulator, balanced at the factory so it runs quietly at idle and at speed.

Charging output depends on rotational speed and on the electrical load. A unit that produces 14.2V at idle with the lights off can still be marginal when the fan, lights and rear demister are all running, which is why a load test matters more than a no-load voltage reading.

Specification Summary

• Rated voltage: 12V
• Rated output: 90 A
• Pulley: 4-groove PK
• Regulator: integrated, machine sensed
• Application: pickup
• Net weight: approximately 5.5 kg
• Condition: new, direct replacement for the original unit

The 12V, 90A rating is the output the unit holds at normal engine speed with the battery in a partially discharged state — the condition that matters in real use, not on a test bench.

Reference Numbers and Cross References

The alternator is supplied against the following references, which help identify it against the unit already fitted to the vehicle:

• 3701020A-E01
• 3701020A-E00
• 1plug

Several numbers in this list refer to the complete assembly while others cover the bare machine. A photograph of the rear cover protects against the most common ordering error. This unit is listed with 3 references in total.

Matching the Unit to the Vehicle

pickup models in this range share the same mounting bracket and belt layout, which is why one reference serves several years of production. Fitment is decided by the number on the unit, not by the model year alone.

If the number on the old alternator falls outside the list above, send the engine code and a photograph of the rear cover before ordering. A unit with the right housing but a different regulator plug will not connect cleanly.

What Wears Out First

Bearings carry the rotor at engine speed for the life of the vehicle. Once the front bearing dries out, the unit starts to whine, and the noise gets worse with electrical load rather than with engine speed alone.

Oil mist from a leaking cam or crank seal attacks the internal insulation. A unit that is oily on the outside is often already failing inside, even if the output still looks normal on a meter.

Diagnostic Signs

• Battery warning lamp glowing at idle and fading at speed
• Headlights that brighten when the engine is revved
• Battery flat after a few days of short trips
• Whine or rumble that rises with electrical load
• Burning smell from the alternator after a long drive

A load test separates a tired alternator from a tired battery. Switch on the lights, blower and rear demister and watch the voltage: a healthy unit holds its output, a worn one sags.

Checks Before Installation

• Battery state of charge and age
• Condition of the B+ cable and its fuse
• Pulley type: solid, clutch or overrunning
• Mounting ear dimensions against the bracket
• Belt routing after the new unit is fitted

A new alternator on a tired battery or a glazed belt will not restore charging. Test the simple items before the unit goes on.

Fitting the Replacement

With the battery isolated, relieve the belt tension, disconnect the B+ terminal and unplug the regulator connector, then remove the mounting bolts and lift the unit out.

Fit the replacement, reconnect the plug and B+ cable, then refit the belt and set tension to specification. Start the engine and confirm charging voltage at idle before the first drive.

Quality Control and Supply from Hejian Nuojin Auto Parts Co., Ltd.

Hejian Nuojin Auto Parts Co., Ltd. produces starter and alternator components for the aftermarket. Each alternator is tested for output at idle and rated speed, ripple current, regulator voltage and bearing noise before packing.

Common references are held in stock, volume orders ship in around 30 days and every unit carries a one-year warranty against manufacturing defects.

Frequently Asked Questions

What charging voltage should I see?

Around 13.8 to 14.7V at idle on a 12V system, and about 27.5 to 28.5V on a 24V system, measured at the battery posts.

Why does the battery light glow at idle?

Usually a worn regulator, a slipping belt or a diode fault. Check belt tension and charging voltage before replacing the unit.

Can I replace the regulator only?

Yes, when the bearings and diodes are sound. On a high-mileage unit the complete alternator is usually better value.

Does the alternator come with a pulley?

Yes, the unit is supplied with its pulley fitted as shown in the photographs, so the original belt can be reused.