1989 Ski-Doo Repair Manual, Page 411Get this manual
Section 04 ELECTRICAL Sub-section 06 (TESTING PROCEDURE)
VOLTAGE REGULATOR INSPECTION
A faulty voltage regulator is often responsible of frequent burned bulbs
TESTING PROCEDURE
The regulator ground must be checked to ensure tho circuit is completeIf necessary, connect good ground wire from the regulator to the engine
A) Quick test without voltmeter
In case of voltmeter is not on hand, visual test can be performed with satisfactory resultDisconnect all lights and electric equipmentWhile engine is running, disconnect and connect regulator connector several times checking for sparkA spark on regulator terminal indicates good and working regulator
B) Voltmeter test