Bucket Truck Testing: The Importance of Having Your Upper Controller Tested

If you’re a bucket truck owner, and you were asked whether you have your upper controller tested, would you know what they were talking about? What if they called it the “joystick”, or “ISO-Grip”? Most individuals are not aware that most bucket trucks are equipped with, what ANSI A92.2 calls “Upper Controls with High Electric Resistance Components”. This is the upper control located at the platform (bucket), that operators use to easily maneuver the boom into position, with the ease of one hand. FYI, “ISO-Grip” is the registered trademark name of Altec’s Upper Controller, but is commonly used by end users when talking about this component, for all makes and models.

Anyway, no matter what it’s called, if the upper controller is considered to be “insulating”, it must be tested. ANSI A92.2-2021 (the nationally recognized standard for the manufacture and testing of Aerial Lift Devices) States in section 8.2.4(17):

If the aerial lift device has upper controls equipped with high electrical resistance components and the manufacturer so indicates, they shall be maintained as high electrical resistance components and shall be electrically tested per section”

Underneath the external coverings of these controllers, you’ll find fiberglass parts that provide insulation to the operator, if the platform comes in contact with an energized component. We have included some pictures below to hep you find these fiberglass components.

Upper Controller with dust boot covering in place


Upper Controller with dust boot pulled back, exposing fiberglass insulating components


Recently in conducting the required periodic inspection and testing for one of our customers, JM recognized one of these handles to be failing our tests. We notified the customer, and luckily, they were able to overnight receive a replacement from the manufacturer. They installed the assembly onto the unit, and we were able to test and pass the overall truck while still on the customer’s site. The end result being a safe, fully compliant, piece of equipment for them to put back into service.

Our customer was gracious enough to allow us to have the failing assembly, and upon return to our Baton Rouge facility, we were able to inspect further. Upon our inspection, we noticed the reason for its failure. The pictures that follow illustrate the cause of failure.

In a nut shell, the handle came into contact with an energized component. The electricity from that component punctured the fiberglass, travelled underneath the fiberglass, and out to the metal structure that connects the handle assembly to the hydraulic manifold. This is an extreme case that we normally don’t come across, and wanted to share with all to help emphasize the importance of having this component tested. In the pictures you should be able to see a little black dot near the bottom of the piece, with what looks like a gouge mark. This is where we’ve dug into the fiberglass, to find out whether this was actually a carbon trail that was left due to the electricity.

Entrance and exit from the electric current. Notice the singed spot of fiberglass at the top, and the arching at the bottom. Just above the arching at the bottom was where we dug into the fiberglass.

Again, the entrance and exit points. The lightly shaded green line connecting the two points traces the path of electrical burning. May be a little harder to see in this picture, but once again you can see the spot where we’ve dug into the fiberglass.

Side profile picture of the component. In this picture you can really see the raised line of fiberglass, that connects entry to exit, where the electricity punctured the fiberglass, travelled down and out of the bottom.

This really is an amazing picture, and illustrates the dangers of high votlage!

            If you haven’t realized the importance of these insulators, obviously that being to protect the operator from suffering an electric shock while maneuvering the platform, then there…there it is. That’s the importance. Whether the operator is wearing gloves or not, there’s still some potential for an incident to occur. This is why ANSI states that these MUST be maintained as resistive components; cleaned, serviced, inspected, and tested. Inspection and cleaning shall be done on a frequent basis; and on a periodic basis, inspection, cleaning, and testing shall be performed. This should be done by your current testing provider.


JM conducts all dielectric tests on Bucket Trucks and Diggers, as required by ANSI A92.2 & ANSI A10.31.

The next time your testing service provider is at your facility, ask them whether they test the upper controls of these units. If they don’t……it may be best for you to think twice.

Brandon B. De Ramus