How to Replace an Alternator on an Isuzu Bighorn

An Isuzu Bighorn alternator should always be tested with a fully charged and inspected battery. A partially charged battery or one with a bad or shorted cell will cause false readings on the amount of charge the battery is producing. An alternator that is trying to charge a battery with a bad cell shows a lower than standard reading and works at too high a duty cycle, which causes it to heat up. It could ruin an alternator if the battery is not changed.

Things You'll Need

• Set of wrenches
• 3/8-inch drive ratchet
• Set of 3/8-inch drive sockets

Instructions

1. Loosen the top bolt and the lower pivot bolt with a 3/8-inch drive socket. Allow the alternator to rotate downward, releasing the tension on the belt. Remove the accessory belt.

2. Disconnect the negative terminal on the battery with a wrench. Disconnect the electrical connector on the back of the alternator by pulling it out. Remove the main battery line on the back of the alternator with a wrench. Remove the top and bottom bolts and remove the alternator.

3. Install the new alternator on the bracket, bolting in the top and bottom bolt. Do not tighten these bolts more than finger tight at this point. Install the main battery wire to the rear of the alternator on the battery+ post and tighten with a wrench.

4. Push the plastic electrical connector into its terminal on the back of the alternator. Install the accessory belt and pull the alternator up by hand and keeping tension on the alternator, tighten the bottom bolt with the 3/8-inch drive socket. Tighten the top bolt and check the tension. To apply more tension if needed, slightly loosen the two bolts and pull up with a little more force and tighten the bolts again.

5. Re-connect the negative battery terminal and tighten securely with a wrench.

References

• Don Bowman, A.S.E. Certified Mechanic