Jumper King, Multi-Jumper with Selector

Product works well. Has every imaginable adapter combination. Comes in a nice sturdy case with elastic holders for all the adapters. Still has room for your personal jumpers and/or some wire. The over all size is bigger then expected, definitely not a pocket tool. Like the built in circuit breaker, allows for tracing issues on equipment with 3 amp blown fuses.

The good: This is an extremely useful tool to bypass the thermostat and safely test all low voltage functions on HVAC appliances. Its has every tool you could need to tap into control wiring, and it has enough extra space in its zipup tool pouch that you can carry lots of minutia you may want to carry along, such as 3a and 5a fuses for the RTU control board you may find has been blown once you get on the roof thereby saving you a trip back to your truck, tips and probes for your multimeter, and other such electrical accessories. Overall it has been very useful for troubleshooting and even for just regular preventative maintenance operations checks. It is worth the space it takes up over a regular jumper wire. The bad: Quality control is lacking on this product. During my first month using it, bare wire slipped out of the plugged portion on one of my jumper leads. It took some time to figure out what went wrong, but basically behind the insulated rubber covering on the prong, the wire uses a simple flathead nut to secure the wire to the prong, and apparently this prong's nut was loose. I appreciate that this results in something that is field serviceable (it is difficult, but using a regular control screwdriver I was able to take off the rubber covering, access the nut, and tighten it up enough to hold the wire again), but this is poor engineering in my opinion. I am going to have to check and tighten all the prongs on this device myself, and make it a habit to give a tug test to each individual wire each time I make use of it, and frankly I don't feel like I should have to do this. When I purchase a dedicated tool that does exactly one thing, I expect it to do it very well. Wires straight up tugging loose after such light usage bodes ill for the long term quality of this device, and as such I can only give a hesitant recommendation for other HVAC/R service technicians. Were it easier to access and tighten the screws that secure the wires, I'd rate it higher.