Using a Test Light to Bypass a Switch Input Signal

You can find more information on this topic in the chapter 2 playlist on my website!

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[rhkips]

Test lights are incredibly versatile and powerful tools! I just had a very similar situation on a 13 Ford F250 window switch yesterday. The shop had been tinkering with it for a couple hours when I walked in to look at a different vehicle, and before they could even finish telling me what had happened, I had verified circuit type and integrity, and was upside-down under the dash locating a blown fuse for the front window motor relay control circuit.

The things you teach are so absolutely critical, and I can confirm that all this knowlege continues to carry through with vehicles manfuctured in 2024, and becomes more and more important every day as control circuits become more and more complex.

Honestly Paul, as soon as I have my house paid off, I really should start sending you a significant portion of my paychecks, or donate that portion to a charity of your choosing. I owe you a lot, and I appreciate you more than you'll ever know!

[spelunkerd]

These lessons are gold, I often think of you when doing them.

[richard]

Paul is a top notch Auto technician who knows his stuff. Appreciate his videos.

[calholli]

The term "pull down circuit" always threw me off like it's something special or different than a normal circuit. But all it really means is that we are on the GROUND side of the load; and the only reason why it shows voltage is because the ground is disconnected. But when you apply the ground (which is what the switch does)--- it pulls the circuit down to it's natural state in the closed circuit which is: a ground. This used to be so mystifying to me and hard to grasp; but once you get it, it's actually very simple.

The key thing to repeat over and over-- that most people will not understand at first, because it's counter intuitive is: That the "GROUND" side of a load will show voltage when it's disconnected. That's one thing that throws people off; because it's the ground side of the motor-- why would it have a voltage? But it does. That's the one missing piece that keeps people from understanding this type of setup.

I took 2 years of electronics in Vo-tech and I still never knew this until I seen you explain it on a white board.
and I'm a certified general electronics technician. :)
I just hadn't ever been taught that simple understanding, weirdly enough. We always studied closed circuits and how they work. Not how to trouble shoot them when they are open or broken.

[Bansheebuzz]

HI Paul. Good to see someone post a video on test lights. I myself run my own workshop in Australia and specialise in electrical diagnostic and repairs. You knew there had to be someone pipe up and say how bad test lights are and that you shouldn't use them. These people clearly don't understand a series curcuit and the effect of the resistance of the bulb can be a very usful tool. Test lights have multiple uses if you know how to use one and understand the system your working on. There is no need to go to the scope or scan tool for every fault and people often skip the basics.

[isalmankhan]

Today I applied the same test on a 23 yaris mirror switch😅
Amazing, Thanks for sharing SD, STAY BLESSED🙏🏻🙏🏻🙏🏻

[diagnosticosh]

Hello, my English is not very good but I understand your video perfectly. Thank you very much for taking the time to share your knowledge.
Jose Mexicano 🤙

[minnow]

Mr Paul, ive been watching you for years. ive learned so much from you, your the Best Thank You

[joejordan]

Hey Paul this is quite a coincidence that you put this video up because I was working on my problematic driver side window switch the other day. I disconnected the window switch module and jumpered the wiring to the window motor in order to roll the window up for the night but when I reconnected the module, the driver side window switch worked fine so I think it was just bad contact with one of the two wiring conectors
that plug into the module switch .
I have loved wiring diagrams ever since I was a kid so I bought and studied every service manual(s) to every vehicle I've owned.

[tracydiller]

Great video Paul as and lesson as always. Been watching Jim's Automotive machine shop on the machining work of you engine. Amazing process. Been in a few machine shops love the smell LOL. Pray for your mom and family may GOD continue to bless you and your family.

[keitharvd]

Just got the sixth edition of the engine performance diagnostic book today man is there some cool stuff in there!!! Thanks man freaking awesome!!!

[CharlesLease-eiee]

I’ve done that trick few times and yes it does work LED light will still slightly light, but it will pull at the ground

[dieselfixr]

That is a great way to test the whole circuit right at the switch location.

[rrmech]

Hi Paul
It's your old friend Richard
Pull up and Pull down circuits
Great stuff

[DDescalchuk]

Basically the same thing is done when checking which wires run the locks when doing pre checks on wire colours when installing a remote start. Low current test light and just supplying a safe ground through an incandescent test light.

Also works when checking a low ref circuit from a pcm/ecm that’s suspected to have failed internally in the module. Hook to a ground back probe module connector or your preferred method of circuit checking ( since technically piercing a hole in the weather pack seal is considered just as bad as wire piercing )

[brian]

Takes me second to catch what you’re saying, but I appreciate all these lessons! Case in point, you measured the voltage and got 11.07, which I read as 110.7 like you’d see in your house! lol.

[grantbellinger]

Wonderful teacher, Beautiful, your videos have an aura of enjoyable learning to me, thank you, Beautiful!

[TheRealTailGateTech]

Another great Danner lesson. Thank you.

[exitmastertec]

Ambient lighting install could result in taking a certain voltage pull setting codes from modules

[PaulR]

Paul/Caleb,
Thank you for this.
Paul (in MA)