multi meter ?

[rbig1]

When you use a multi meter to check power. Do you know you really have useable power? Or should you use a automotive bulb of the correct LOAD to verify? Just a observation from use. Ever happen to you yet? Also have you earned any other test facts?

[sldunker]

I always use a test light along with the meter. It is good to have a load on the circuit.

[uncledj]

A load is good. I've found that when dealing with electronics, it's very possible to register voltage on a meter without potential.

At the risk of revealing that I don't know much about electronics, I think it's called a TRIAC or something like that, where the aforementioned voltage closes the "gate" which allows the current to flow.

When testing a circuit being controlled by electronics I do make sure there's a load. Keeping in mind a load is typically a solenoid coil, but the "phantom" voltage does not have the potential to energize the coil.

Hope that helps more than cornfuses.

[djh3]

Just because you have voltage, dont mean its going to do anything. The definition we teach is "the potential to do work". I have checked many a battery with 12v that will hardly light a turn signal. Amps is what ya need to make it do the work.

[Patch]

Good stuff guys!

Rod you know how I feel about this and also what I use when I'm shooting a problem.

Of course I haven't the fancy equipment you have but then again I do keep more girlfriends and so less disposable tool kit $$$

 

But for others reading, one strand will show continuity or proper voltage yet not have the capacity for load.

Coils or windings produce the resistance assuming that is what we are shooting at, without that you have a dead short.

If we have voltage that measures well but can't carry the required amperage then its kind like a knock at the door only the muscle needed to actuate the door simply isn't present...

 

The other side that trips some of us is the return or grounds completing the circuit, if the ground can't handle the load the same happens but on the other side of the door...

 

Signal voltage is different tho, we are not looking for muscle we are actually reading the noise it makes and so care must be taken when shooting controls such as electronic modules.

[djh3]

Good stuff guys!

Rod you know how I feel about this and also what I use when I'm shooting a problem.

Of course I haven't the fancy equipment you have but then again I do keep more girlfriends and so less disposable tool kit $$$

 

But for others reading, one strand will show continuity or proper voltage yet not have the capacity for load.

Coils or windings produce the resistance assuming that is what we are shooting at, without that you have a dead short.

If we have voltage that measures well but can't carry the required amperage then its kind like a knock at the door only the muscle needed to actuate the door simply isn't present...

 

The other side that trips some of us is the return or grounds completing the circuit, if the ground can't handle the load the same happens but on the other side of the door...

 

Signal voltage is different tho, we are not looking for muscle we are actually reading the noise it makes and so care must be taken when shooting controls such as electronic modules.

 

Very well explained. We show in the Auto Tech class the 1 strand wire thing. We have actually run a small light bulb on the wire and cut strands and eventually it just melts the wire because to much of a load for the size of the wire. Also your last bit there on signal voltage is good to note if you go to troubleshooting CAN Bus stuff. Test lights are out folks. They can cause to much draw and fry the module. I have read the LED test lights are less likely but the regular bulb jobs just draw to much. Try to keep my guys and gals straight. If it dont work and the fuse is burned its a short. If fuse is good its an open.

[Patch]

Very well explained. We show in the Auto Tech class the 1 strand wire thing. We have actually run a small light bulb on the wire and cut strands and eventually it just melts the wire because to much of a load for the size of the wire. Also your last bit there on signal voltage is good to note if you go to troubleshooting CAN Bus stuff. Test lights are out folks. They can cause to much draw and fry the module. I have read the LED test lights are less likely but the regular bulb jobs just draw to much. Try to keep my guys and gals straight. If it dont work and the fuse is burned its a short. If fuse is good its an open.

 

 

Rod and I have had many conversations regarding troubleshooting, he is quite diverse with regards to his projects so we click well. I had tried to set up a class with Rod for a couple of planned troubleshooting small projects to "pass it forward" to the young guys that often drop by my shop. Why, was to show how 2 old guys growing up before the computer controls had to learn logic and apply theory and, the bond that goes with old guys and old toys.

 

That said you are fortunate djh3 to work with young minds on a regular basis, teach a man to fish is after all the next best thing to being a Father.

 

Where many of the inexperienced fall off is not being able to visualize a problem. So what I like to do is consider myself and how difficult it was for me to absorb organized thoughts from another, at their pace.

 

An example is Rod was holding the tissue box for me when in the space of a week I got back to burnt meters from young guys; I had had them for 20 years! lol Tho one had a 2 year theory certificate he had no practical and reversed the poles on my Tracer... I assumed and I accept that I failed him.

(just to continue a sec) the boys wanted to replace the Tracer and sent me a link to what they thought was suitable, well too expensive I replied, but between us, really to complicated! lol

 

A quick on noise: noise is read as wave forms, finding noise that makes no sense is for the more experienced and, is very difficult to teach forward.

 

The old test lights work very well on these older rides we run. In a lot of ways it reminds me of a carpenters square.

Versing hookups teaches as well as it answers. Most use or think the light can only be used on one side of the circuit but the magic is on the other side!

Brightness of a light you are use to negates the immediate need for a meter, now not if we are on this side of the world and the problem on the other side, we need numbers.

 

 

How many examples can you guys provide thru the use of a test light?

Dim/bright

and no light,

what about a flashing light, what would cause that? What if the flash is consistent? (this may be best served with a LED prob) Why?

testing the return side of a circuited: reverse the connections and lightly drag the tip the signal should be both audible and visual right; now you have proved the ground because you loaded it! Same condition: bright light leading to the suspect///signal should be both audible and visual after the suspect, the suspect is at fault if the light and prob don't perform as mentioned ( for whatever the reason) !

Simple and quick tricks, but when you get into it it can be fun, and can be fun to teach.

 

Harnesses are way too often overlooked causing parts to be replaced that are not defective, especially in the modern systems.

Edited September 10, 2020 by Patch

[Flyinfool]

Most diagnostic system will tell you the module that is causing the problem, So you replace it and find the problem is still there, That is when you have to ditch the puters and bring in an old guy that has a clue to find the real problem. Or worse yet the bad module was only a symptom of the real problem, and now you have 2 burned out modules. Again bring in the old guy.

 

I had a bad wire deep in the wire harness, it was a 10 AWG wire that was not used with my option package, it just ended in the middle of the wire harness, BUT it was fused at 40A. With age the insulation shrunk a bit and left strands exposed and they managed to work their way through the insulation of some of the neighboring wires and cause all kinds of shorts that were enough to melt tint 20 ga wires but not enough to pop the 40A fuse. as those wires melted they then contacted other neighbors in the harness and it got real ugly. There were a bunch of modules that were destroyed. Had I just replaced any one of them the new one would have been instantly destroyed. It took me 2 weeks working full time and a lot of $$$ in parts to track and repair all the wires and burnt out modules and get everything back working.

 

This used a combination of both incandescent and LED test lights, both incandescent and LED continuity testers, and a good meter to figure out what was all going on.