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Voltage Regulator

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Regulator rectifier voltage regulator

Oldtimer controller - rectifier test

If the measured voltage at the battery exceeds approx. 14.4 V when increasing the motor speed, the voltage regulator is defective.
Oldtimers are still mechanically adjustable regulator models and with separate rectifier. These regulators must be readjusted in the event of overvoltage.

Test separate rectifier

Disconnect the rectifier.
Resistance measurement with multimeter (diode measurement),
Measured values ??between plus and all other lines.
Also between minus and all other lines, including one polarity change (change the measuring line).
Measurement should be in one direction, eg. in the forward direction show a value about 8-10 times lower resistance than in the other direction of measurement = reverse direction.
If this is not the case, the rectifier is defective.

Current regulators have installed the rectifier and regulator in one housing.

Current voltage regulator on the motorcycle
Shunt regulator (cross controller)
For permanently excited alternators mostly so-called shunt regulators are used for the voltage conversion.
The cross controller converts excess energy supplied by the alternator via a resistor (shunt) into heat.


Overheating of the regulators and this regulation also converts part of the power in the stator winding into heat.
The alternator always runs at 100% with this regulation.
With strong alternators (eg Aprilia RSV1000 approx. 500W), this continuous load may cause overheating of the insulation of the winding wire and thus short circuits in the coil towers (windings).
Shunt regulators are implemented in thyristor or MOS technology.
Due to the MOS design of the controller less power losses occur, thus the controller is not quite as hot as when constructed in thyristor technology.

linear regulators


Regulator works differently:

When the battery is full, the voltage regulator interrupts the stator circuit, causing the alternator
no more power supplies. The temperature of the stator is thus lower and overheating of the bobbin towers is less likely.
Only approx. 50% current load of the stator winding when using a longitudinal instead of a shunt regulator.
Longitudinal regulator Product No .: MTP18088, with adapter plug set Art.No .: MTP18088SET (similar to SH847AA)
This series regulator works without problems even at higher speeds and currents (short-term load up to approx. 50A at 13.5V tested by us).

Battery Charge Checking Errors - Problems:

Test all contacts and wires from the controller, alternator and battery.
Are the leads tight and firmly connected to the battery with clean contacts?
Are the lines dirty or scorched?
Are the plugs scorched?
Ground connections not oxidized?
Are the connectors of controller and Lima firm and clean?
Is there a leakage current? (Leakage current less 1 mA)

Failures due to battery cell closure:

1. The battery may discharge suddenly.
2. If the battery is not causing a short circuit, all readings will be correct.
3. The voltage regulator is overloaded by a short circuit (or position shortage) in the battery.
4. The battery can be charged again (presumably the position is not effective)

Measure step by step:

Engine is off, voltage at the battery (open circuit voltage approx. 12.5V -12.9V)
Voltage at the battery when starting (about 10V - 11V)
Motor runs over 3000 rpm, voltage at the battery without consumers (about 13.5 V - 14.5 V) at over 14.5 V is the controller is broken.
Voltage at the battery when consumers are switched on (about 12,6V- 14V under 12,5V is possibly the Stator defect)
Motor is off and if you turn on a consumer (eg. Light) breaks the battery voltage below 11V together. Presumably the battery is defective then.
Or typical ground fault / corrosion or loose battery contacts!
Engine stops, motorcycle stops, motorcycle does not start, engine
does not start, battery overflows, battery puffs up, battery dead, battery dead, no charging voltage at the battery, too little voltage, charge controller, dynamo,