Finding Low Voltage Shorts Fast! HVAC Troubleshooting!

In this HVAC Training Video, I show How to Quickly Find Low Voltage Shorts with a Multimeter! Once you know where to look and how to divide the wiring, troubleshooting the problem can be done fast! Supervision is needed by a licensed HVACR Tech while performing tasks as Experience and Apprenticeship garners Wisdom and Safety.

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[cutabove]

Let me suggest a method for finding low voltage shorts without removing all those wires. First I'll be obvious, the reason the fuse is blowing is because something is shorted and therefore has very low resistance or zero resistance drawing lots of current and causing the fuse to blow. The temporary solution is to add series resistance (inline with the fuse or replacing it) to the circuit with a known level of resistance drawing less current than the rated fuse. The simple answer is to insert a 24 volt bulb in a socket with two wires or a commercial short finder (all these things are is a 24 volt bulb packaged nicely with wires). The current draw will be 2.5/3.0 amps which isn't enough to blow the fuse. The bulb will light because you have 24 volts on one side and the short giving you a ground on the other side. Grab your multimeter and wrap the current jaws around each low voltage wire on the control board until you find the wire/circuit drawing 2.5/3.0. That is the wire/circuit where your short is. Now track that wire to its termination point which could be a component. Disconnect the component and if the light goes out you found your shorted device. If it doesn't track that wire along its length to find where the wire is touching another wire or the frame of the furnace. In any case you cut your troubleshooting of the short down to five or ten minutes. You can use the same procedure on a cars, but use a 12 volt bulb. I've used this process for years to track down short on cars, furnaces and even circuit boards. I've found the current jaws on a multimeter the most underutilized item in a tool bag. Hope you find this useful.

[moeselec]

Low voltage Shorts are time consuming and can get frustrating . Your "process of elimination" is well explained . I find this video very helpful to deal with this issue. Thank you very much for sharing this video.👍😊

[jericosha]

Dude I know you made this due to feedback. You're awesome!

[justinwallace]

This is a great explanation for the process of elimination. I would also recommend to especially younger technicians to get a Lil Popper fuse reset tool or something similar. They come in 3 amp and 5 amp sizes. They are helpful during the troubleshooting process so that you aren’t just burning through fuses.

[iateyourmic]

This video helped me diagnose a short to ground from our humidifier, which was causing our ecobee to only call for heat for less than a second, and the 3 amp fuse on the furnace board to blow when contacting Rc and W1. Turns out one of the wires poking through a sharp hole in the cold air return got nicked, who knew?!

Thank you so much, you've saved me a bunch of trouble and money.

[eevalobo]

To keep from making one million trips wire a T-stat to carry w/ you for the amount of wiring you need. You can use 2H/1C T-Stats for furnaces if you wire the W to your Emergency Heat in your diagnoses T-Stat. If it’s a Heat Pump set then just continue as the wiring should be applied. Attic trips are a killer, don’t forget your fuse pop switch so you don’t burn through fuses.

[CaptainBobSVChimera]

Not sure how old this video is but it was tremendously helpful to let me today. While my problem turned out to be something unique (an unused wire from the contractor coil outside had lost the electrical tape that was shielding it and it was arcing on the cabinet) . using your guide, I was able to determine everything it was not which eventually led me outside to look at the contractor coil. Thank you!!!!

[grecomsiri]

Beautiful, this trade is becoming more easier watching you sir. Thank you!

[MrDmadness]

For boards I often find thermal imaging shows the blown component ( seek thermal pro for smartphone ) you can also usually spot the hot flash of the groundcshort asthe fuse trips... excellent video as always

[sgalford]

Wanted to give a big thanks. Had the dreaded 3amp fuse issue on a 4yr old carrier split system. Out of all the videos I watched yours by far was the easiest to follow and quickest to resolution. Thanks for sharing your knowledge.

[kitchenratt]

I’ve done refrigeration for 30 years, I don’t get much practice on home units. Very informative! Thanks for sharing!!

[Phemsdasla]

it is the best channel for HAVC systems ... welldone man

[dillonchalk]

Your vids are top notch and have helped me become a better tech for my customers and business partners! Thanks a million sir.

[Falcon-ehtq]

This is great, helps narrow down the search to 1 run. Thank you.

[romarro]

As always thank you for sharing your thoughts and knowledge

[gillcorona]

You are a Great! teacher for that reason i purchased your books.

[JoseTorres-ouue]

Very knowledgeable and straightforward thank you.

[cutabove]

Want to find a short even faster than my suggested method using current jaws? First, use the technique explained in my previous post by adding serial resistance with a 24 volt bulb in place of the fuse or in series with it. This will prevent the circuit from blowing the fuse while allowing it to remain active drawing somewhere around 2.5 amps. Next drag out a Thermal Imaging Camera and look over the wires and control board (remember all wires whether from the thermostat or outside units terminate at the control board). The shorted circuit will be obvious. Thermal imaging cameras can be had pretty cheap these days and worth adding to your tool kit. Hope this suggestion helps in your troubleshooting.

[paulklingele]

Fantastic explanation! This helped me isolate my yellow wire which was shorting -- it was wrapped over the edge of a housing where the access door would rub on it every time the door was opened, slowly fraying the wire until it finally made contact with the housing creating a short.

[TaddyDigest]

Great video I love the set up the app it's a great learning