Testing Fuses
Thread Starter
Intermediate
Joined: Jun 2025
Posts: 25
Likes: 7
From: Charleston,SC
Testing Fuses
I need to test the fuse and fuse connection points as my instrument panel lights are not working. I am using a multimeter and understand how to test the fuse itself but wanted advice on how to confirm if there is good connection between the fuse and connection points (don't know the correct term for the two "saddles" that hold the fuse) when the circuit is hot. Trying to rule out corrosion. Dealing with electricity is not my area of expertise and don't want to accidently do something that causes a bigger issue. Is it as simple as one multimeter probe touches the connection point and one touches the adjacent fuse side to confirm continuity? I would assume it's a bad idea to touch both connection points (each end of fuse) at the same time it seems like this would circumvent the fuse. Am I correct in that?
Le Mans Master
Joined: May 2005
Posts: 7,348
Likes: 2,272
From: Central Maryland
Set your meter to measure DC volts. If the meter isn't an auto-ranging meter, make sure it's set to measure at least 20 volts DC. Touch one probe to chassis ground. Touch the other probe to the fuse holder contacts on one side of the fuse. Then move that probe to the contacts on the other side of the fuse. If you see battery voltage at the contacts on both sides of the fuse, all should be well with the contacts.
Live well,
SJW
Live well,
SJW
Last edited by SJW; May 18, 2026 at 01:08 PM.
Instructor
Joined: Dec 2025
Posts: 231
Likes: 77
From: Pachuta, MS
This is a bit difficult in that probing the fuse contacts can easily make or break the connection but if it does then the fuse contacts are too loose. About the best you can do is put the DVM in DC volts mode and ground the common lead and then probe both sides of the fuse. Any difference in the two readings indicates a problem. Some circuits are powered all the time, some with ignition 'ON' (except for start) and some are powered by the lights. Your most likely culprit if all the instruments lights are out is the rheostat in the headlamp switch especially if the turn signal and hi beam indicators work. If they don't work as well then look for bad grounds. If the tail lights don't work then fix them first because the tail light circuit feeds the instrument lamp rheostat.
Last edited by acstephenson; May 18, 2026 at 01:12 PM.
Drifting
Joined: May 2023
Posts: 1,348
Likes: 1,003
From: Sierra Vista, AZ
I use a test light, and poke the tip on the ends of the fuse, and both of the clips that the fuse fits into. And yes, you can make a fuse start working just by doing this, if corrosion is the problem, and the fuse itself is still good.
Race Director
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From: San Antonio, TX/Mahopac, NY
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I just went through this with my new to me ‘64 coupe. Several things weren’t working as they had no power, but the fuses were good. I replaced the fuses anyway and cleaned the fuse box terminals with a small wire brush on a Dremel (battery disconnected of course). I reinstalled the fuses with a tiny amount of dielectric grease…just a tiny smear. Everything started working.
Tech Contributor
Joined: Jan 2007
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From: Dyer, IN
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Brett Foote
Team Owner
Joined: Jul 2006
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From: Kannapolis NC
Basic check for contact with the fuse. With your black meter lead on ground, the metal part of the fuse should read the same voltage as the clip that holds it in. There will be no voltage on the inst gauge fuse unless the lights are on and the rheostat run counterclockwise, and the voltage will diminish to zero as you rotate the rheostat clockwise. That will be the case on both sides of the fuse and there should be no voltage difference shown on the meter when you switch from one side to the other. The voltage comes into the fuse on the left side (as you look at the box) and the other end connects to the wire that goes to all the bulbs (gray). As mentioned before, you also won't have that voltage if the tail light fuse is blown, or the rheostat bad or turned clockwise.
Last edited by 65GGvert; May 18, 2026 at 04:06 PM.
Drifting
Joined: Sep 2024
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From: Florida
Years ago I had a small outboard ski boat with a 120 horse Johnson.. I had a continual crank/no start condition for years that I could not figure out.. A bit disheartening to be in the middle of the lake and the engine won't start.. It always started after fooling with it or letting it sit for a while... There was one only inline glass fuse, like our C2 cars, on the engine.. I looked and tested it many times.. Finally I had the fuse out and one of the silver metal ends fell off....... Aha moment... New fuse and I never had a problem with it again....
Cheap insurance to replace those old fuses due to age......
Cheap insurance to replace those old fuses due to age......
Last edited by Limp; May 18, 2026 at 05:27 PM.
Thread Starter
Intermediate
Joined: Jun 2025
Posts: 25
Likes: 7
From: Charleston,SC
UPDATE - I checked the fuses for both the panel lights and tail lights and they are both good. However, when I turned on the lights and made sure the rheostat was turned correctly, I tested the connectors for the panel fuse and no voltage. Even made sure to scratch it some to ensure no corrosion was causing it. I checked the connectors for the tail lights (which are not working) and there was 12v both sides of the fuse