Electrical Tools

[RichardNew]

Here's a Vintage Motorsport column from last year. It deals with electrical tools you might need.



Richard Newton
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[redridge]

a multimeter is 95% all you need... IMHO.

[mclmk8d]

Richard,
Nice simple article, as are your other articles on your blog; just bookmarked!
I was reading the 2008 article about the Porsche Project and your problems with alignment. I'm wondering which shop you use...I'm in Coconut Creek and use KMW in Boca. Kevin and his crew are great if you're ever on this coast.
Serge

[RichardNew]

This one has gotten even more interesting. When that problem was happening I did all of the usual things like swapping tires from side to side, etc. Nothing made a difference. I knew it had to be an alignment problem. I mean I used to teach this stuff to techs in various dealerships.

Then I decided to take the 911 up to Sebring for a track day. I put a set of new Michelin DOT tires (same size) on the car. The pull went away. What? How can that be? The pull had to be in the tires. Couldn't be. Yes it has to be.

When I got back from Sebring (it's a 2 hour drive for me) I put the street Michelins back on and the pull returned.

I'm still trying to explain this one. If it really is a tire issue then when I swap the tires side to side the pull should change directions. I'm still thinking about this one.

Richard Newton

[Tidybuoy]

My biggest challenge I have when dealing with electrical issues is that I can never figure out what to set the multi-meter to. For example, one knob says .00, .000, .0000, etc and I don't remember the other.

I always have to get my neighbor to help me do it right and he always does but he never explains it in a way that makes any sense (i.e., ohh, just set it to omms, 001 etc.. or worse yet, he tells me it dosen't matter where I set it to)

I'm guessing at the actual terms here since I don't have the multi-meter here with me at work (as I am goofing off).

Vern

[mreid]

Here's a quick primer:

- for continuity (checking to see if a connection is solid), set the ohm setting to its lowest value. You want it to be as close to zero as possible, so multiplying by the smallest number gives you the most accurate reading. This will be 90% of your uses for the resistance scale.

- always make sure the power is completely off or battery disconnected when checking any resistance. The meter uses its internal battery to send a calibrated current through the circuit being tested and you will disrupt the test or damage your meter if you use it on an energized circuit.

- if you are checking a wire that runs from one end of the car to the other and want to make sure it is intact, test it to ground first using the Rx1 scale (hold the meter leads together first and adjust the "zero" until the meter reads zero. This is how the meter calibrates the current for the test). If the wire is not grounded, ground one end and then test the other end by touching one lead to the wire and the other end to a good ground (chassis). The closer the meter reads to zero the better. If the meter doesn't deflect at all, you either are on the wrong wire or the wire is broken (mouse probably chewed it like the bastard chewed many of mine).

- you can also use the ohm setting to check your senders. This is the other 10%. To accurately test the device you have to isolate it. The best way is to unplug it and then test the device with no wires connected.

Those are the typical uses for the "ohm" settings. There are plenty more for volts and amps.

[T77911S]

Originally Posted by redridge

a multimeter is 95% all you need... IMHO.

if you ever did electrical work on cars for a living, you might change your mind.

test light.

i have a MM but rarely use it. when i worked on cars, we had a tester that checked the battery and alt. save the MM for when you need to know the actual voltage level. when you have a $400 MM, you dont bang it around when a $10 test light will do.

i have seen this problem on this site more than once.
someone is checking voltage with a MM and they read 12v, but the circuit still does not work. here is why.
a MM is a high resistance very very low current "load". a light bulb is a low resistance, higher current load. high resistance reduces the amount of current to the load. so something like a bad connection that has high resistance will show 12v on a MM but will not light the light due to low current.
this has actually led to poeple over looking the problem and going down the wrong road to fix their problem when it was a simple connection issue.
to make it worse, they get on here and tell everyone they have 12v at the socket and the speculations really start to fly, making the issue even worse.
a test light would have led these people to the correct problem because it uses a higher current device, a light bulb.

so, just because you measure 12v at the end of a wire with a MM, that does not mean that wire is good. i would even go as far as to say that you could measure 0ohms and it still not be good.

imagine just ONE strand of a wire making contact. that could measure 0ohms but still may not provide current to the load. what if the yellow wire to the starter was like this? if it did not melt due to the current, you could have 0ohms and no start.

like the poster said above.
most dont know what they are reading when they use a MM. this does not mean dont try to learn, but someone could interpret the readings the wrong way.

ever been upside down under a dash with one arm twisted all around and the other underneith of you? try reading a MM. looking at a light is much easier.

save the MM for reading battey voltage when you have charging issues or starting issues.

DO NOT USE a test light on fuel injection. there are some older systems you can use it on, but just dont do it.
they make an LED test light that will work for FI,