Questions and Answers

Toyota Charge Light Q. Hello and thanks for taking the time to hear my small, but irritating electrical problem. 1986 Toyota Pickup Extended Cab SR-5 22RE (2.4 Cyl.) Fuel Injected Manual (5 - Speed) 168,000 miles Power Steering, A/C

Problem:
Charge light comes on and goes off "whenever" it wants to. I have had the alternator checked and it is fine. After having the alternator checked, I tightened up the alternator belt to see if that was the problem. To my surprise, the "charge" light went off and the voltage hand went back to normal.

After a couple of days went by, the "charge" light has again came on and now stays on constantly. I am at a loss as to what the problem could be. I use a Haynes manual for any work I do to my vehicle and the only other possible explanations are either the battery (which is only a year old), a fusible link, or possible a bad voltage gauge. The wiring diagram in the Haynes manual is very complicated and there are so many wires under the hood that it is almost impossible to trace the wires for any bad connections.

I thought it was strange that when I tightened the alternator belt up, I had no problems for several days and all of a sudden, the charge light has once again came on. I have done everything I know possible to correct this minor problem, but I'm at my wits end and really don't want to take the truck to someone since I do almost all the work myself. Having the battery checked will be my last known solution. The battery was bought at Advance Auto and that could possibly be the problem.

If you have any suggestions I would be very thankful to hear them. Once again, thanks for taking the time to hear my rather irritating problem.

Chris

A. A problem like this can be difficult to find. An understanding of wiring diagrams is essential to successful electrical troubleshooting. Don't look at the whole diagram, just look at the charging circuit, that will make it a lot easier to understand. Since the light is on constantly now, it should make it easier to locate.

First thing to do is to make sure all the connections are clean and tight. Pull back the protective covers on the terminals and make sure there are no broken wires. Also make sure all the fuses are good. I know a few guys, myself included, who got bit by forgetting this step.

Here is the procedure to accurately test the alternator. If the alternator checks out as good, then the problem is in the wiring and you'll have to trace it out.

1. Disconnect the wire from terminal B of the alternator and connect it to the negative terminal of the ammeter.
2. Connect the test lead from the positive terminal of the ammeter to terminal B of the alternator.
3. Connect the positive lead of the voltmeter to terminal B of the alternator.
4. Connect the negative lead of the voltmeter to ground.

Circuit Test Without Load

1. With the engine running from idling to 2000 rpm, check the reading on the ammeter and voltmeter.

   Standard Amperage: Less than 10 amps

   Standard Voltage: 13.5 - 15.1 volts at 77°F (25°C)

2. If the voltage reading is greater than spec, replace the IC regulator. Ground Terminal F
3. If the voltage reading is less than spec ground terminal F of the alternator, start the engine and check the voltage reading of terminal B.
4. If the voltage reading is greater than spec, replace the IC regulator.
5. If the voltage reading is less than spec, replace the alternator.

Circuit Test Under Load

1. With the engine running at 2000 rpm, turn on the high beam headlights, place the heater fan control on HI, then check the ammeter.

   Standard Amperage: More than 30 amps

2. If the ammeter reading is less than 30 amps, replace the alternator.

NOTE: With the battery fully charged, sometimes the indication will be less than 30 amps.

Additional Information provided courtesy of ALLDATA

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