No its the tool that measures electricity you are gonna need one this fluke is a quality one thats not crazy money. https://smile.amazon.com/dp/B00JT5RUUU/ref=cm_sw_r_cp_apa_fabt1_ELYQFb6NK3JYC?_encoding=UTF8&psc=1 Learn how to use one. It will help you in all kind of things. I would also check that something didn't kill the battery while it sat and that all of your ground connections are good.
Honestly Fluke has a 40$ one that doesn’t check ampacity, and that’s fine for the majority of commercial work. Small / lightweight / portable, all things that I’d value if I was needing to have tools on me constantly.
Fluke 101 Basic Digital Multimeter Pocket Portable Meter Equipment Industrial https://www.amazon.com/dp/B00JT5RUUU/ref=cm_sw_r_cp_api_glt_fabc_PP5KYJ2HRJSZ5N6RARHS
If you need the amp clamp and amps on leads then get this, but most of the time it’s not really applicable
Fluke 323 True-RMS Clamp Meter https://www.amazon.com/dp/B00AQKIEXY/ref=cm_sw_r_cp_api_glt_fabc_E8Q6KNZCBBNJZPR0STZT?_encoding=UTF8&psc=1
Fluke 101. https://www.amazon.com/Fluke-101-Multimeter-Equipment-Industrial/dp/B00JT5RUUU It's not loaded with functions, but it has the important features and do them well.
The plug in the picture doesn't look like mains, that's too small for that. It looks very much like a standard 0.1" pitch pin header. Most likely some low voltage control circuit. A multimeter to check continuity of the wire and then to measure presence of any voltage on the plug would be best to check this. I recommend this Fluke:
https://www.amazon.co.uk/Fluke-101-Multimeter-Equipment-Industrial/dp/B00JT5RUUU
It is safe even for mains (there are cheaper meters but none are safe to use on mains!) and pretty much idiot/mistake proof so you won't blow anything up even if you are really hamfisted with it.
OTOH, if you are really not sure what you are doing, call an electrician and don't mess with the wiring yourself. You could easily kill yourself or someone else and/or set the house on fire. And I am pretty sure the insurance will refuse to cover any damage that would result from such DIY "repair", because it is not legal to work on it unless you are a certified electrician.
I have one of these. It's pretty basic, but solid.
https://www.amazon.com/Fluke-101-Multimeter-Equipment-Industrial/dp/B00JT5RUUU/
The Klein non-contact tester is fine, and will detect voltage reliably. I own one myself.
If you are looking for a digital multi-meter that can be used to help troubleshoot the Fluke 101 is a good meter to start of with http://www.amazon.com/Fluke-101-Multimeter-Equipment-Industrial/dp/B00JT5RUUU/ref=sr_1_6?ie=UTF8&qid=1455012823&sr=8-6&keywords=fluke+multimeter
The Fluke 87 is the Granddaddy - top of the line http://www.amazon.com/Fluke-FLUKE-87-V-Digital-Multimeter/dp/B0002YFD1K/ref=sr_1_1?ie=UTF8&qid=1455012998&sr=8-1&keywords=fluke+87
and anything in between should work.