Test lights for checking a circuit under load

[atikovi]

I've been watching a few South Main videos where he replaces the suspected bad part with a homemade test light to verify it's getting enough current, as a voltmeter or electronic test light wouldn't put any load on it and produce a false conclusion. Go to 8:45:


What bulb can you use for those tests? Any tool company sell them in a test kit?

 

[spackard]

I think he made his own from junkyard luminaries.
Stop lamp, running lamp, low-beam should be enough of a variety.
That would roughly be 27W, 11W, 35W.

 

[Rick505]

Like stated above, I seem to recall he did a video, at least one, where he showed how he created these test lamps. I believe he even drilled a hole into the cap of a spray can to run the wires/lamp base in to sort of protecting the "bulb" glass on some of them.

 

[Trav]

One of these may be the type of tool you are looking for.

Amazon.com: Electronic Specialties 185 48V LOADpro Dynamic Test Lead : Automotive

Buy Electronic Specialties 185 48V LOADpro Dynamic Test Lead: Tools - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

Amazon.com

 

[mccandish]

Like stated above, I seem to recall he did a video, at least one, where he showed how he created these test lamps. I believe he even drilled a hole into the cap of a spray can to run the wires/lamp base in to sort of protecting the "bulb" glass on some of them.

Good memory on you!

 

[atikovi]

One of these may be the type of tool you are looking for.

Amazon.com: Electronic Specialties 185 48V LOADpro Dynamic Test Lead : Automotive

Buy Electronic Specialties 185 48V LOADpro Dynamic Test Lead: Tools - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

Amazon.com

I did look at that, thanks, but a bulb that draws an amp or two would give a quick visual check of a weak or corroded connection or wiring problem.

Good memory on you!

Yea that's it. Will make some of those.

 

[Timmastertech]

The key when using a load to substitute for the load that a component places on the circuit is that you need to size your substitute load appropriately to match the load that the component places on the circuit. For example, your average a/c compressor clutch draws 3-4 amps of current. A 9006 headlamp works well to substitute that load. A 150 milliamp standard testlamp isnt enough load for that circuit. Conversely, that 9006 bulb is far too much load to substitute for a purge valve and would cause either PCM driver damage on a driver without overload protection or the driver to turn itself off if it has overload protection. I have 4-5 different lamps that I use to load a circuit depending on the load that circuit is expected to carry

 

[wtd]

I made three test lights out of light connectors I pulled off of our junk 94 Cavalier that is out in the field. I attached alligator clips to the end of the wires to use with T pins or banana clips. I used a headlight connector and harness, a side marker one and a turn signal one.

I then measured the amp draw with a multimeter for each light so I would know how many amps they draw.

This company makes two different test lamps with stacked banana ends if you don't want to make your own but they are kind of expensive and you have to provide the bulbs.

Jarhead Diagnostics Products — Shop — Jarhead Diagnostics

www.jarheaddiag.com

Go under the Jarhead Diagnostics Products tab on the left side of the screen and you will find both light kits in there. One is a high amp load light and the other is around a 2 amp load one

 

[DIY4quality]

The key when using a load to substitute for the load that a component places on the circuit is that you need to size your substitute load appropriately to match the load that the component places on the circuit. For example, your average a/c compressor clutch draws 3-4 amps of current. A 9006 headlamp works well to substitute that load. A 150 milliamp standard testlamp isnt enough load for that circuit. Conversely, that 9006 bulb is far too much load to substitute for a purge valve and would cause either PCM driver damage on a driver without overload protection or the driver to turn itself off if it has overload protection. I have 4-5 different lamps that I use to load a circuit depending on the load that circuit is expected to carry

Is this really true? The LoadPro tester (Amazon link) places only 0.5 amps of load on a 12v circuit. The inventor of this tool (Dan Sullivan) indicates that a half amp of current is sufficient to perform a voltage drop test to detect corrosion or a dodgy connection that is a circuit fault. This is a different method than simply measuring resistance with an ohm meter which places a tiny load and will show continuity where there may be a fault under greater load.

So how much current is really needed by an external test load to detect a circuit fault? A starter can draw hundreds of amps. Is 0.5 amps sufficient?

 

[supton]

So how much current is really needed by an external test load to detect a circuit fault? A starter can draw hundreds of amps. Is 0.5 amps sufficient?

How much is sufficient? clearly 0.5A would not be if testing the path to the starter--or overkill if testing the wiring to a door switch.

Usually low current paths are easily tested with low currents like this, as the path is there or isn't. High current paths that are just not low ohm enough usually can be felt/seen when the insulation gets hot and/or melts.

 

[DIY4quality]

The LoadPro tester contains a 25 ohm power resistor to draw the 0.5A at 12v. Too bad it doesn't have a selector switch for several resistor values so you can choose your load value.

 

[mattd]

a head light bulb is fairly standard to load test a circuit.