Shop Press

Shop Press is the news and idea hub for everything related to working on cars and trucks, focusing on repair, technology, and wrenching lifestyle.

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Politics Ain’t Politic

Red, blue, or green? You’ve pieced together the point of this article by now, no doubt. This will not be a piece that risks raising the hackles of those who are deeply political. That’s not because you’re encouraged to avoid the topic, but instead, to do what makes...

Belt Noise – ASE Practice Question (VIDEO)

Description Technician A says that "chirp" is the most common type of noise complaint customers bring to the shop. Technician B says that EPDM belts can be worn out yet pass a visual inspection. Who is correct?A) Technician AB) Technician BC) Both Technician A and BD)...

Diagnosing a Prius Coolant Leak (VIDEO)

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A Crash Course on Modern Impact Sensors

We’ve come a long way since the automotive impact detector was developed decades ago. One clever design used a metal ball in a tube that would move to complete a circuit during a collision. This rudimentary accelerometer proved that the idea of detecting a collision...

Alignment and Inner Tie Rod Play – ASE Practice Question (VIDEO)

Description A vehicle equipped with a MacPherson strut suspension is in the shop for new tires and an alignment. The technician notes play in the left-side inner tie rod end. What should the technician tell the customer?A) The play will not affect the vehicle's...

Put the Second Floor to Work

Paying the mortgage (or the rent) on the bricks—the actual shop itself—is an expense. (A fixed cost, if you want to be particular.) But that building does more than keep your tools and techs dry. It provides room to work and house equipment. And if you’re like most...

Check Out This Hacky Diag Tool

by | Apr 3, 2025

Disclaimer: Dorman Products purchased this kit at full price.

In the interest of serious investigative reporting, I swiped the Shop Press credit card for $14.83 to try out a diag tool I thought looked super-cool: the relay bypass. What’s that? Short version: Imagine a relay-shaped manual SPST switch.

Longer version: A relay, at its core, is an electrically actuated switch. A relay bypass replaces that function with a manual switch. Some bright soul got the idea to take six common relays and fit them with on-off rocker switches, the end result possessing the common “footprints” for automotive (“ice cube style”) relays. They can then be swapped into a vehicle fuse box or power center to give a technician manual control of the item receiving power.

Brilliant.

Now I thought Andy’s find of resettable breakers in a fuse footprint was interesting, but I was a little dubious about how often I might reach for them as a tech. But these babies? I feel a little differently.

What do I love here? A few things. I can test a component and its controlling relay for function at the same time. I don’t have to look up pinouts for common relays that I forget every time. I don’t have to open up a relay and put power to it to see if it’s working. I don’t have to build/scrounge/dig for stuff to make jumper wires. These sort of turn diagging relays from a painful punishment into something super-fast.

There’s really only one downside I can see: some of these are fitted with 10A switches, and they’re not fused. So, y’know, ya gotta use ‘em with caution or you’ll blow up one of your new toys. But that doesn’t seem like a very expensive proposition to me.

You know when I’m gonna use these? The next time someone brings me in a full fuel tank on a job where it needs to come down. Fuel caddy. Hmmph!

Now I thought Andy’s find of resettable breakers in a fuse footprint was interesting, but I was a little dubious about how often I might reach for them as a tech. But these babies? I feel a little differently.

What do I love here? A few things. I can test a component and its controlling relay for function at the same time. I don’t have to look up pinouts for common relays that I forget every time. I don’t have to open up a relay and put power to it to see if it’s working. I don’t have to build/scrounge/dig for stuff to make jumper wires. These sort of turn diagging relays from a painful punishment into something super-fast.

There’s really only one downside I can see: some of these are fitted with 10A switches, and they’re not fused. So, y’know, ya gotta use ‘em with caution or you’ll blow up one of your new toys. But that doesn’t seem like a very expensive proposition to me.

You know when I’m gonna use these? The next time someone brings me in a full fuel tank on a job where it needs to come down. Fuel caddy. Hmmph!

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