Simple question:

How in the world do I use a voltmeter? I am a total newb in the electrical field and rather want to know how to use one properly than stick them up my nostrils (have no other use for it).

Anyway, I think I shorted something out while fixing a few fuses in my car. The dashboard blinkers stopped lighting up, the trip A and B miles reset, temperature starts from 125 degrees F, the homelink and clock both do not work. I've searched and found the fuse to be at the driverside kick panel fusebox under "ELEC PARTS" in black. Too bad... the fuse looks legit and even swapped it out with no solution. This is where the voltmeter should come in...

... so, how do I use one?

 

to see if a fuse is blown, (sometimes visually checking it doesnt work) set your voltmeter to ohms or continuity... touch each probe to one side of the fuse (doesnt matter, you're gonna get a reading) if you read "OFL" it means its blown. it stands for "Over Fcken Load", in laymans terms. if you have a reading, then it is good.

to see if there is power, you set your voltmeter to DC and connect the red probe on top of the fuse (it has a little metal showing) which should be already placed in the fuse holder. if you get a reading, the you have power.

in your case, it sounds like you have a short to ground my friend. trace the wire and see where it is pinched.

 

you were trying to "fix your fuses"? explain.

 

Had a customer who tried to fix his fuse "problem" with a paper clip, melted some wires really good! Made his wiring harness into a fuseable link.

If the fuse blows you got a dead short in the circuit somewhere, could be in the conductor or it may be in the device it serves.

 

In short, my taillights stopped working, so I replaced the fuse for that. Suddenly, my center console lights stopped working as well, so I replaced the fuse for that. Next, problems with the clock, homelink and dashboard accessories occurred. I didn't do anything extravagant... only replaced a few fuses.

What do you mean by "short to ground"? What do you mean by pinched? Do I expect a blown up ground wire or something?

I wouldn't do any **** like that as I am fully aware of what a fuse is for (basically a bumper beam for frontal impact, except similar for the electrical harness/circuitry).
So, in other words... if the fuse was not blown, then the wires that connect to that particular fuse is pretty much ****ed up? If that's the case, I have to trace the wire, correct?

Thanks guys.. I'm learning a lot.

 

Also don't replace a fuse with a high amp fuse. Such as don't replace a 20 amp fuse into 5 amp place.

 

When you replaced the fuse for the taillights did they start working again?

How about the center console lights?

To measure voltage in a car you need to make sure your black probe is grounded to the car - this can be achieved by touching any exposed metal in the car because the ground terminal of the battery is connected directly to the body of the car (making all the connected metal pieces ground).

In a pinch, you can use the screws that hold the visors to the headliner - that seems to be a good ground on every car I've ever worked on. Another place to grab a quick ground is the metal outside of the cigarette lighter (don't touch the center pin in the very bottom). If you have an alligator clip on the end of your black probe your best bet would be to look up under the drivers dash and find a metal bracket to attach the lead to - you really can't go wrong that way.

Once you have a solid ground you can then set your meter to DC volts. If you don't have an autoranging meter then you would set it to the 20 scale or something along those lines (the smallest available number above 15). You can now check anything in the car for voltage.

 

I replaced the fuse with the exact spec fuse (ie: 10a red for a 10a red, etc).

When I replaced the fuse for the taillights, they started working again, but caused another fuse to blow out.

Thanks for the advice. It's time to purchase a voltmeter. Must I need a specific one or any voltmeter would work?

 

From what you said it sounds like you have a short circuit since replacing the fuse caused several other fuses to blow..

Those are much more difficult to troubleshoot than open circuits and it'll be difficult to find it with a voltmeter..

Typically the way you'd troubleshoot a short in an electrical system is by disconnecting each load one by one to try to isolate and localize the problem area..

I'd do what several other people said and look for any physical damage in any of the wiring.. hopefully its obvious..

 

Do you have any alarms aftermarket radio connected to the original wiring ??

 

Damn... that means I have to pull out each wire and inspect them physically?

Yes I do. However, I don't know if that's a problem or not... Alarm is working fine.

 

By replacing one fuse you shouldn't cause other fuses to blow, it is actually impossible for that to happen.

Fuses are done in a tree like fashion, typically one or two big fuses feed 3-6 medium fuses that feed 15-20 smaller circuits. When you have a problem with one of the smaller circuits it will blow the fuse immediately behind the problem (and sometimes, if it is bad enough, the medium fuse behind the immediate fuse). When you replace the fuse, you are simply reconnecting the load to the electrical system. This can NOT, by itself, cause fuses on the same level (ie parallel fuses) to blow. Now, if you replaced the fuse and it blew the medium fuse then that would make sense (and you might have a bad fuse).

The best way to track down the issue is to identify EVERY component protected by that specific fuse. Next, replace the fuse with a brand new one. If the fuse blows instantly then you have a direct short to ground on the load side (output) of that fuse. If it does NOT blow immediately turn on / activate each device one by one that the fuse protects. If the fuse pops note the last device you turned on / activated. This will identify the wiring that you need to investigate. I have found, in my experiance, once you get to that point the best way to troubleshoot is:
1. look for any obvious damage
2. Remove any removable devices (light bulbs, added accessories, etc.)
3. cut the wire in half (or close to it) and use a meter to determine what side of the wire the short is on (will measure close to 0 ohms to ground). That will narrow down where the prloblem is (fuse box side or device side).

Electrical problems arn't fun, but with the right information (service manual) and a little patience you will get through it!

 

That remark about the paper clip as a fuse was not directed at you, it was just a funny thing I remembered and I felt like sharing.

First is you need to know what devices are being protected by the fuses that are being blown

Next is you would like to follow the wires back from the fuse box to the devices so you can look for a short to ground. I would unplug the harness at all points possible coming from the fuse and including the devices being protected by the fuse. From the fuse holder to ground you should now have infinite resistance (no shorts).

Plug back in the connector closest to the fuse box and the check again for a short circuit. If it is shorted the problem is in the section of wires, if not continue on plugging in stuff until the short reappears and tells you where the problem is.

I find harnesses almost never cause any problems (unless the vehicle is new) unless someone has cut into them or tried to modify them. Almost always the problem is with some device such as the door switch for the interior light, a sensor which got too old or some other device thats broken.

I wish you Good luck on tracking down your faulty device.

 

Well... I feel stupid.

I bought the voltmeter and extra fresh fuses (just in case). I popped in the fresh fuse and it worked.

I have no clue what the hell just happened... but the odds of 2 spare fuses that looked legit not working baffled the crap out of me.

Since I have a voltmeter that I don't use, I might as well play around with the probes by sticking them up my nostrils (again).

Thanks again for the advice and notes... I certainly learned a lot this past few days.

 

You may still get a chance to use your meter, it is very rare for a fuse to just blow up for no reason, but then again sometime we get defective fuses.

Anyhow it's a really good excuse to run out and buy a new tool and a meter is a handy tool to have around for the car and the house.