17 votes
Accepted

How to test a bolted-in heavy duty 50a / 80a / 100a fuse with a multimeter without removing it?

Instead of Ohms checks of fuses I check for voltage with power on. Set your voltmeter to DC volts with the negative lead on the battery negative connector. With the positive lead test both sides of ...
Fred Wilson's user avatar
  • 11.6k
12 votes
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Multimeter - Basic Functionality and Howto

Basic Functionality Image In order to illustrate a typical Multimeter The Multimeter is specifically a multifunction tool. By definition it combines several, well defined instruments and multiplexes ...
crasic's user avatar
  • 496
10 votes
Accepted

Can I use a digital multimeter in resistance mode on a "no-load" circuit?

In "measure resistance" mode, the DMM (Digital Multi Meter) uses an op-amp (Operational Amplifier) to put a constant current across the probes. It then measures the voltage drop that results, and by ...
cdunn's user avatar
  • 9,296
9 votes
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I shorted the alternator for a second with a multimeter set to measure current

No, you most likely didn't mess anything on the car up, though you might have fried your multimeter. If the vehicle still runs and nothing seems messed up, more than likely nothing is. Something you ...
Pᴀᴜʟsᴛᴇʀ2's user avatar
7 votes

How to test a bolted-in heavy duty 50a / 80a / 100a fuse with a multimeter without removing it?

If you can get to both sides of the fuse, see if you have power on each side. If you want to make sure, remove the battery terminal, and use an ohmmeter to measure the resistance between the battery ...
X-tech2's user avatar
  • 779
6 votes

Why do dealers want their technicians to use True RMS multi meters?

The difference between a "true RMS" meter and a plain old garden variety AC meter is the ability to accurately measure the voltage of non-sinusoidal waveforms, for example a square wave. "Normal" ...
dlu's user avatar
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6 votes

How to Test an Ignition Coil with a Multimeter

There are three tests that can be preformed using a multi meter. A DIS type coil that services two cylinders works like a transformer. The primary windings are controller by the ECU. The secondary ...
vini_i's user avatar
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5 votes

Multimeter to check car battery current

To check the battery voltage a meter is connected in parallel. This involves touching the black lead to the negative battery terminal and the red lead to the positive battery. In this configuration ...
vini_i's user avatar
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4 votes

Multimeter - Basic Functionality and Howto

Basic Functions A multimeter is an electrical device for measuring electrical Voltages (Volts, V), Currents (Amps, I) and Resistances (Ohms, Ω). Most are also capable of measuring continuity, and ...
Nick C's user avatar
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4 votes
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How to Test an Ignition Coil with a Multimeter

To be honest you won't get far with a DVOM. While vini_i's answer is correct you can't do this while the car is running. You should be looking into buying a digital storage oscilloscope if you want ...
Ben's user avatar
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4 votes

I shorted the alternator for a second with a multimeter set to measure current

You did no damage to the car with this. If your DMM does not have a fuse, you may have ruined the amp part of the DMM. If you measure a known amp source and get an accurate reading your good to go. If ...
Jupiter's user avatar
  • 3,197
3 votes

Can you attach multimeter to battery terminals while car running/charging?

Yes, obviously, otherwise how would you measure the charging voltage. The most likely error was having the multimeter leads connected to the current measuring terminals on the multimeter, when they ...
Solar Mike's user avatar
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3 votes

Multimeter to check car battery current

The safest way to test if you're not SURE of what you're doing (and to avoid other issues like bad lead connections) is to use a clamp meter. These are capable of measuring AC and DC voltage and ...
StevoInco's user avatar
  • 251
3 votes

Multimeter - Basic Functionality and Howto

Looks more like 4 questions lol. But here goes. Basic Functions : Multiple Ranges for measuring Volts, Ohms (resistance), and Milliamps. Headlamd failure: Negative or black lead to a good ground (...
Three Quarterton's user avatar
2 votes

How do you test analogue electrical circuits?

Created by Reddit User Waynep712222
NitrusInc's user avatar
  • 763
2 votes

How to Test an Ignition Coil with a Multimeter

I was poking through the 98 US WSM and found this:
Robert S. Barnes's user avatar
2 votes
Accepted

What is the proper scale to use when measuring infinite resistance

If the manual says that there should be infinite resistance, then you need to test using the highest range on you DMM. If you have a M ohm range, then use that. Do not rely on the continuity range ...
HandyHowie's user avatar
  • 25.2k
2 votes

Block heater or cord?

I live in Texas, so I don't even really know what a block heater is, but I know electronics, and an open circuit means that something is broken (or a switch is open, but I don't think there are any ...
JPhi1618's user avatar
  • 13.2k
2 votes

Blown fuse on car by using multimeter

The other possibility is that with the + probe you touched earth or ground at the same time as the live terminal or wire - sometimes making a small probe extension is good. I have used a paper clip ...
Solar Mike's user avatar
  • 34.6k
2 votes
Accepted

Battery drain but multi meter shows it doesn't

Lead acid batteries can be very deceiving about the amount of charge the have stored. A new battery may be able to provide the current to run a starter motor for several minutes, whereas an old or ...
HandyHowie's user avatar
  • 25.2k
1 vote

I shorted the alternator for a second with a multimeter set to measure current

No parasitic drain, your alternator is charging your battery, everything is working. You are good. You need a new battery.
MJH's user avatar
  • 878
1 vote

Upstream O2 sensor stays at 0.4V

I am thinking you are measuring reference voltage to an A\F O2 sensor. Reference voltage is usually between 2.5 and 4 volts. If there are 4 or more wires, this is most likely the case. Also A\F ...
Jupiter's user avatar
  • 3,197
1 vote

Electrical Diagnostic Procedural Lists

There is this Guide, from /u/waynep712222 on Reddit, on Voltage Drop Testing:
NitrusInc's user avatar
  • 763
1 vote

What is the proper scale to use when measuring infinite resistance

The manual states that the ground must be totally insulated from point 2. The highest range is the correct setting here to begin with. If any resistance (conductance is the better word here) is ...
Bart's user avatar
  • 2,954
1 vote

Why do dealers want their technicians to use True RMS multi meters?

It's about measuring the "odd" waveforms: wheel sensors, crank sensors cam position sensors that are square or sawtooth in form, rms means "root mean square" that is square all the individual values, ...
Solar Mike's user avatar
  • 34.6k
1 vote

How to Test an Ignition Coil with a Multimeter

If you are looking for misfires then you best shot would be is to hook up a scanner tool, start the car and go through the statistics in the scanner which shows you about the misfires and a lot more ...
kasey's user avatar
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