Alternator / Voltage Regulator

[davids2toys]

Originally Posted by patrickt

You can't measure amps that way. In fact, you can't measure resistance that way either. So, put that completely out of your mind. With the circuit breaker connected, and some electrical loads running (like lights and fans) your inductive ammeter will tell you the current that is running through that circuit, but a voltage drop test will tell you if that circuit breaker, or a connection, or a wire, is creating a bottleneck -- and that's what you really want to know.

AYIYIYI
So what is the purpose for the ohms function on the multi-meter if it is useless. I did a quick Google search on voltage drop test and in what I do understand, it makes sense!

[Grubby]

Ohm function is great for finding opens in the circuits. A bad relay, faulty heating elements like in your stove are all easy with the OHM function.

It is very good for finding a poor connection in electrical connectors.

If you measure resistance across many electrical items and compare a known good one with a questionable part, you can usually find the problem.

I frequently use the feature when chasing electrical problems in the house or garage.

A typical quality DVM can handle 20A in series. That is enough to check most automotive circuits. Look at your fuses; most are 10A and 20A. The starter is more than 20A draw.

A good quality Fluke or other DVM is a must have if you work on cars.


John

[patrickt]

Originally Posted by davids2toys

AYIYIYI
So what is the purpose for the ohms function on the multi-meter if it is useless. I did a quick Google search on voltage drop test and in what I do understand, it makes sense!

Well, completely useless may be an overstatement. The only times I actually measure ohms in an automotive troubleshooting situation, as opposed to just using my ohm meter as a glorified test light, are: 1) When I have the manufacturer's troubleshooting instructions that specify what the resistance must be on a particular piece of hardware (common); 2) I am comparing two pieces of hardware to see if there is an obvious and big difference (rarely); 3) I am performing the "jiggle" test (common).

If I'm tracking down a bad connection, I use the voltage drop test. I think that's the number one electrical test that shade tree mechanics, working on "old school" type of cars, should be familiar with. You're right, there are lots of videos showing how to use the Voltage Drop Test -- it's pretty easy to learn.