Charging System: Testing and Inspection
Alternator and Regulator Test1. First make sure you have a good battery, and that the alternator belt, and connections at the alternator and main fuses are good.
Next, check the No. 2 (15 A) fuse in the dash fuse box. (If blown, the charge warning light will come on even if the system's working properly).
Start the engine and allow it to warm up (cooling fan comes on).
2. Disconnect the alternator connector from the alternator.
With the ignition switch on, there should be battery voltage between the IG (BLK/YEL) terminal and body ground.
^ If there is no voltage, check for an open in the BLK/YEL wire between the dash fuse box and the voltage regulator.
^ If there is battery voltage, go to step 3.
3. Following the manufacturer's instructions, connect the SUN VAT-40 (or equivalent) and turn the selector switch to the "Starting (No. 1)" position.
4. Start the engine. Turn off all accessories, move the selector switch to the "Charging (No. 2)" position, remove the inductive pick-up, and zero the ammeter.
Reconnect the inductive pick-up to the battery ground wire, so the arrow is pointing away from the battery.
5. Raise engine speed to 2,000 rpm and hold (make sure cooling fans are off.)
Apply a "load" with the carbon pile, so the voltage drops to no less than 12 volts.
Check the maximum amperage reading and compare with the chart below.
NOTE: Subtract 5 to 10 amperes from the maximum reading due to engine operation.
^ If amperage is within specification, the system is OK: Proceed to the Charge Warning Light Test.
^ If amperage is not within specification, go to step 6.
6. Perform full field test: Attach a probe to the VAT-40 full field test lead and insert the probe into the full field access hole at the back of the alternator. Switch the field selector to the "A (Ground)". position momentarily and check amperage reading.
NOTE: As an alternative, use a screwdriver and an ammeter to full field the alternator.
CAUTION: The voltage will rise quickly when the alternator is full fielded. Do not allow the voltage to exceed 18 volts, or damage to the electrical system may result.
^ If the amperage is within specification, replace the regulator.
^ If the amperage is not within specification, replace the alternator.