How To Check Fuses With a Multimeter 

Thanks! That’s my goal!

Amen to that bro

What volt is the fuse supposed to be?

@thehomicidalduck6867 It depends on voltage of circut being tested. Automotive is 12 volt. House is 120 / 240. Industrial 277 / 480.. You have proven a little bit of knowledge is dangerous. You should not be making videos like this, knowing so little. Be safe. Shut off power. Remove fuse then use your ohm meter

Yeah well you just freaked me out... ugh! I thought I had it. Clearly I don't!

No problem 👍

Ye u can u go try it for yourself put a blwn fuse in and a good one and try both u will see

yep. thankfully newer (and good) meters have safety built into them to prevent damage to the meters, or at least that's what i've heard. but, going back to basics, this is def not how u do it... unless u disconnect the battery, which is another context missing in this video

If you test for voltage what reading would tell you if the fuse is good or not ? Im just asking idk

@@buffalo_662112v on both ends measuring from the same “zero” somewhere (ie. zero voltage drop on the fuse itself)

12 volts on either side of the fuse

Yes much faster

Not as practical because power is not always running through the fuses unless the component is on whereas continuity can be tested whether the component is on or off.

I have been doing this with cheap meters and bit more expensive. Never had an issue . Working on 12v and 24v vehicles now for 18 years. Many times tested fuses like this. And got a few that was blown that you could see there is defently a short circuit.

@frikkiesmit327 why not measure the voltage on either side of the fuse? Or even measure a voltage across the fuse? You won't subject your meter to voltage on the resistance range that way. Any good meter today won't care, but old digital meters and analog meters could be damaged by subjecting them to a voltage while on the resistance range. Trust me, it happened to me. Yes, I'm going back maybe 45 years, but think what you are applying to the meter! It's fine to check continuity across a fuse with the power removed, but in your example the power from the battery is still applied to one side of the fuse, any device that the fuse powers up will be taking the other side of that fuse to ground, probably at low impedance, meaning there will potentially be 12v across the fuse, if it's blown. Like I said, modern equipment today won't care, but older equipment could possibly be damaged. Would you measure a fuse like that on a mains powered piece of equipment while it's plugged in and powered on? Probably not !! And why not? Because of a possible damaging potential across the fuse !! It's the same principal ! If your equipment is modern, i.e., 18 years in the automotive trade, then I would not expect it to get damaged. I go back 50 years! Yes, all my Fluke,Tektronics, Bryman, and even most of the cheap Chinese equipment today won't care. But with something old, you could be taking a gamble.

I blew a tester using this method. You would think nothing would happen when testing across one wire, but if the fuse is open, you may actually subject the tester to voltage.

Stop spreading stupidity

Voltage meters are open circuits between the probes.

The whole purpose of a fuse is to break that bridge. That literally how and why they work.

@@peterjohnjoseph give it a minute. . . Think. If it breaks in the middle, and you connect a lead to 1 side, through your meter, touching the other side with the other lead, both sides are now bridged. Hence, the meter will bell out for continuity.

How did it go? Hope it all is back in order and working again!

@@Malahoko well I pulled codes looking to make sure the other o2 sensor didn't go out. but it's a p0420, turns out the catalytic converter has a chunk missing out of it. pieces bouncing around in the muffler. anyway, there were a bunch of u2100 (I think) codes that all pointed to the clock spring being the culprit. as I later found out the cruise control doesn't work either. so now I have to pull the steering wheel apart and check resistance across the clock spring... not something I want to do if it turns out to not be the problem.

Yes

@@nicholaslombardo9696 thank you!

Yes it will. This is called continuety test. You can also test electrical cables just make sure they are not plugged in the 110v ac or 220. You can also test the switching sides on relays , you can also test other switches as well. Multimeter is to me a must have. Makes life so much easier and prevents one from making costly mistakes.

It's an ohms check. To test resistance, power should be off. It's also a great way to test if power is short to ground also.

@dewilliams2012 thank you!

So if it says the fuse is bad, you remove the fuse and test it again with the probes on the fuse leads.

Whatever.

If you get a backfeed then meter will display a - on screen and OL ( overload) . I have never gotten that when testing fuses like this. Ive been working on vehicles for 18 years and did test fuses the same way as in video

@@frikkiesmit327meter will not read OL if there is back feed. If there is back feed you will get a reading. It’s best practice to always remove the fuse. Yes it’s faster to probe right across it but in the case there is some back feed like stated your going down a rabbit hole.

it need power from somewhere to work lol

@@danielm94437 not for continuity

In this demonstration remove fuse to test the integrity of the fuse. The multimeter uses its own internal battery for testing continuity.

Doesn't matter

What settings do I put my meter on? I just bought on from harbor freight and I need to check my fuses

@@single_dadthere’s a few ways to check

It’s not about “caring to learn it” 35 plus years forklift/plant & I’ve picked up good pointers here on RU-vid, I’m saying potentially a shared circuit, or someone who has bridged into the circuit further in, or a relay that has snapped internally etc etc could cause a back feed, been in that position. Also, by testing across the fuse, you can’t see the deterioration across the fuse weakest point, been in many a situation where the circuit stops, being mobile a engineer, 2/3 hours later when we turn up fuse has cooled & 2 pieces of fuse are now touching, no fault found, circuit heats up fuse opens across break, don’t have to have a blown fuse to have no circuit, not personal, but I’d rather do my due diligence, job done right, no repeat calls, have a good day.

Just dont use test light on any of the wiring harnasses. You can easily trigger and deploy airbags of a vehicle. It happend to one technician few years ago. Test light the old type which just consists of globe, they are basicly a short with little resistance. The other test lights with leds are safer.

@@frikkiesmit327 well I work on equipment only. lol. But good point.z

No problem!

I had some problem with a 30amp fuse, looked and acted completely normal, had power flow and everything, buy as soon as there was heavy draw I kept having issues, I replaced and isolated everything just to find the fuse was faulty and half connected 😅

@@codypalmer2732fuses breakdown/wear out but don’t blow until what you describe happens, for us mobile engineers the circuit has cooled down, fuse element touches, continuity ok, experience tells me when chasing this type of fault renew fuses.

I hope they do

😂 if they don't have a continuity check mode, they cant choose the "beep" setting.

Then just use voltage mode If there's 12v coming through then it's working

Then check if theres maybe some other main fuses. Check also on back if the wire that goes into port is still secure. It has happend on some cars like a polo v/ wagen which the factory through they were clever to make sure the wires going to fusebox was under tension. So that caused a wire to pull halfway out so fuse didnt even touch the terminals. Which caused the cars centre lock not to work.

And also if the terminal doesnt securely clip inside fusebox than what happens is when you insert fuse, you pushing the terminal away leadinh to bad and no connection.

How?

@@alecpajor9273you can get a back feed from the circuit giving a false reading.

Blown fuse, one side will be 12volts ,the other side earth via the load. Resulting in a blown fuse in the voltmeter. Better to test for voltage to ground.@@alecpajor9273

Yeah tell us how thats so wrong? You more than welcome to remove each fuse by hand and check.