How to test a fuse correctly (not just eyeballing it)

Overview

A fuse can look perfectly fine and still be blown, a hairline break in the metal strip is easy to miss. Testing takes two minutes with a test light or multimeter and removes all doubt. You can also test most fuses without pulling them out.

What you need

• Test light (fastest method) or multimeter
• Flashlight
• Spare fuses of the correct amperage

Quick checks first

1. Confirm whether the circuit needs the key on or off to have power, this affects how you test.
2. Use the correct fuse diagram for your year range before pulling anything.
3. Never replace a fuse with a higher amperage rating.

Test light method (fastest, no pulling required)

1. Set the parking brake. Put the Jeep in Park.
2. Turn the key to the position that powers the circuit (some fuses only have power with key on).
3. Connect the test light clamp to a solid chassis ground.
4. Touch the probe tip to the small test points on top of the fuse.
5. Both sides light up: the fuse is good.
6. Only one side lights up: the fuse is blown, power enters but does not exit.
7. Neither side lights up: the circuit may not have power right now, or there is a feed problem upstream.

Multimeter method

1. Key off. Pull the fuse out.
2. Set the meter to continuity or ohms.
3. Touch the probes to the two metal blades of the fuse.
4. Continuity (or near-zero ohms): fuse is good.
5. No continuity: fuse is blown, replace it.

If that did not fix it

• If the fuse is good, check the relay, switch, wiring, or the component itself.
• If the new fuse blows again, use the Fuse keeps blowing guide.

Videos

• Checking fuses without removing them (YouTube)
• How to test car fuses with a test light (YouTube)

Source links

• CherokeeForum: Jeep Cherokee 1984–1996 Fuse Box Diagram (includes fuse basics)

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