Lyall 37990 Electrical Disconnect Pliers Review: A Good Idea With One Flawed Detail

Introduction

Electrical disconnect pliers exist to solve one specific, frustrating job: releasing stubborn single and double electrical connectors on cars, trucks, and heavy-duty vehicles without breaking the plastic lock tabs. Lyall’s 37990 is a patent-pending entry in this category, and it comes with a feature list that looks right on paper. In practice, though, one design detail undercuts the whole tool on smaller connectors, and it is worth understanding before you spend money.

What the Lyall 37990 Promises

Lyall markets the 37990 as a tool that removes many single and double connectors found on cars, trucks, and heavy-duty vehicles. The selling point is a set of narrow, needle-like tips intended to provide extra grip when working connectors loose in tight spaces. The tips are genuinely slim, which helps them reach connectors buried behind other components, and the tool feels purpose-built rather than like a repurposed generic plier.

The Jaw Geometry Problem

Here is where the design falls short. The jaws are parallel only in their fully closed position. As soon as you open them to grab a connector, the jaw faces angle away from each other, which cuts down the contact area pressing against the connector. On a small connector with a lock tab that needs to be depressed, that means the pliers can only catch a thin edge of the connector body.

The result is predictable: when you squeeze to grip, the tool rolls around the connector instead of holding it. On a first attempt, the connector simply spun out of the jaws. Because the surfaces are only parallel at full closure, there is no way to get more than a tiny sliver of purchase on a small connector, no matter how you position the tips.

Testing a Workshop Fix

To confirm the diagnosis, the same behavior showed up on cheap generic disconnect pliers with identical parallel-at-closure jaw geometry, so this is not a Lyall-only flaw but a common shortcut in the category. The fix concept is simple: measure the jaw gap needed for a typical small connector, around 27mm in this test, and grind the jaw faces so they sit parallel at that working distance instead of only when fully closed.

After grinding the jaws flat to that opening width, the pliers gripped the same connector flush and solid, with no wobble or spin. That demonstrated the concept works: jaws that are parallel at a usable opening distance give a much better grip. Ideally, a manufacturer could design the jaws to be parallel at multiple connector sizes, or offer versions tuned for small and large connectors.

Who Should Still Consider It

The 37990 may still work acceptably on the larger connectors shown in Lyall’s own product materials, where the wider connector body fills the jaws more completely. If most of your disconnect work is on bigger automotive and heavy-duty connectors, the parallel-at-closure issue matters less. If you regularly fight small sensors and tight connector tabs, the grip problem will show up constantly.

Buying Advice

If you are shopping in this category, check the jaws with the pliers opened to the size of the connectors you actually work on. If the faces stay flat and parallel against the connector body, the tool will grip well; if they angle away and touch only at a corner, expect connectors to spin. On that test, the Lyall 37990 does not pass for small connectors, and a cheap generic pair with the same geometry performs no better. The underlying concept is sound and the narrow tips are genuinely useful, so a revised version with parallel jaws at a working opening would be a genuinely excellent tool.

Conclusion

The Lyall 37990 electrical disconnect pliers have the right idea, narrow tips for tight spaces and a focus on automotive connectors, but the jaw geometry gives up most of the grip on small connectors. Unless your work is mostly on larger connectors, it is worth comparing alternatives or checking jaw behavior at working width before buying.