• Hello Guest, welcome to the initial stages of our new platform!
    You can find some additional information about where we are in the process of migrating the board and setting up our new software here

    Thank you for being a part of our community!

Wtf is happening

Testing involves using an old fashioned 'test light' with an incandescent light bulb of ten watts or so installed. The clamp end finds a good ground. The pointed end is used to verify battery voltage.

It is useful for verifying that all the signals needed for a relay to work are present...
That a relay, switch or light bulb is getting power... It's ground is indeed making a ground ect.

Volt meters are mostly useless except for learning that yup! 14 volts when it is charging... Ect.
 
JohnLane said:
Testing involves using an old fashioned 'test light' with an incandescent light bulb of ten watts or so installed. The clamp end finds a good ground. The pointed end is used to verify battery voltage.

It is useful for verifying that all the signals needed for a relay to work are present...
That a relay, switch or light bulb is getting power... It's ground is indeed making a ground ect.

Volt meters are mostly useless except for learning that yup! 14 volts when it is charging... Ect.
Click to expand...

I totally disagree.

I was taught the exact opposite. Test lights are just for quick checks. When it comes to actual diagnostics - DVOMs are king.

Too many times, someone says "I tested it (with a test light)" and the problem is that test lights will light up at 11 volts and higher with very little degree of indication of how low the voltage actually is.

Now, Snap-On makes a test light with a a voltage gauge on it. That is nice ;-)
 
swedefiend said:
I totally disagree.

I was taught the exact opposite. Test lights are just for quick checks. When it comes to actual diagnostics - DVOMs are king.

Too many times, someone says "I tested it (with a test light)" and the problem is that test lights will light up at 11 volts and higher with very little degree of indication of how low the voltage actually is.

Now, Snap-On makes a test light with a a voltage gauge on it. That is nice ;-)
Click to expand...

I like the test light as it pulls enough current in many cases to know that there may be a bad connection that the DVOM says "12.5 volts here... Keep looking."

Obviously there is a place for the DVOM.... More often then not in the toolbox taking up space.

OP... Glad you managed to solve that common problem.
 
Han-Tyumi said:
The in tank fuel pump fails when its warmed up. Solved
Click to expand...

So, to get home when the car's warm, you have to spray starting fluid into a vacuum line? :wtf: Also, dude, get a can of PB, some new exhaust studs and nuts, as well as exhaust port gaskets. Fix that exhaust leak. That way, people on FB don't keep going :lol: when they see your video on the carthrottle page.
 
John242Ti said:
So, to get home when the car's warm, you have to spray starting fluid into a vacuum line? :wtf: Also, dude, get a can of PB, some new exhaust studs and nuts, as well as exhaust port gaskets. Fix that exhaust leak. That way, people on FB don't keep going :lol: when they see your video on the carthrottle page.
Click to expand...

Link?
 
swedefiend said:
I totally disagree.

I was taught the exact opposite. Test lights are just for quick checks. When it comes to actual diagnostics - DVOMs are king.

Too many times, someone says "I tested it (with a test light)" and the problem is that test lights will light up at 11 volts and higher with very little degree of indication of how low the voltage actually is.

Now, Snap-On makes a test light with a a voltage gauge on it. That is nice ;-)
Click to expand...

There is a place for both the test light and the dvom. Test light is actually better in most cases because it also verifies current . I had a window regulator recently that was non operational and I made the mistake of using a dvom to measure voltage, got 12v, installed a new window regulator/motor and it didn't work!@$%. There was a bad connection in the door umbilical, and even though I read 12 whole volts, it wasn't passing enough current to light up a test lamp, or a noid light. Learned my lesson on that one!

There are even test lights now that don't even have a ground wire. Your skin touching to a good ground completes the circuit from the lamp to ground.
 
The test light

I have been formally trained to use the test light to verify circuit operation.


A good use of a dvom is to check for more than 5 ohms resistance in a ground circuit. Or another example is connect to each end of a wire and wiggle test the harness to check for broken wires which may show up as fluctuating resistance.
 
Last edited:
The bottom line is this:

A test light will show you quickly that there is voltage present in a circuit.

A DVOM will quantify voltage, current, Hz and more in the same circuit.
 
Also know that there are times that using a test light can induce operation in a circuit by providing an auxiliary path to ground.

A high Z meter will NOT do that.
 
Last edited:
So let's say you want to verify if a washer pump circuit is good....take out the meter? Ok so you measure 12v at the pump wiring between positive and the negative. Is the circuit OK?
 
ZVOLV said:
So let's say you want to verify if a washer pump circuit is good....take out the meter? Ok so you measure 12v at the pump wiring between positive and the negative. Is the circuit OK?
Click to expand...

Id use a light if I can get the connector loose. But, I'd use my meter with piercing leads if not.
 
Also, nine times out of ten, the pump is bad or it's the ground.

Measure resistance across the pump. High resistance? Seized armature. Infinite resistance? Brushes shot.

If in spec (have to measure a good one or look it up), measure voltage at connection using power and ground from connection. Then, measure voltage using ground at battery. Significant drop? Clean ground, move to fuse block.
 
swedefiend said:
Id use a light if I can get the connector loose. But, I'd use my meter with piercing leads if not.
Click to expand...

Ok so you have now pierced the washer pump wiring and registered 12v between the positive and negative wire, while pressing the switch. Pump is not operating. Replace the pump?

How do you know there isn't a bad connection at the fuse block or a poor ground? Recently I have been becoming a bigger fan of the noid light. Just clip it in and walk back to the switch and then see if it lights up. No bulky wires, or meters, or lamps dangling.

There are times for using each tool. Using a test lamp on computer circuits isn't a good idea, but on higher power stuff like motors I'm using a test light to confirm voltage and current.
 
Last edited:
You must log in or register to reply here.
Back
Top