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When Selling a Job, Get It In Writing (Not an Emoji)

This one’s for anyone who interacts with customers directly: service writers, small shop owners, and even techs who do some moonlighting or side work. Be careful when using text abbreviations, slang, or emojis with your customer, and that goes double when a customer...

The Stories Spark Plugs Have to Tell (VIDEO)

Description In the days of carbureted engines, mechanics would always take a moment to examine the spark plugs they were replacing as part of a routine tune-up. The plugs often provided valuable information as to how well the engine was performing and whether there...

Service Managers: Buy Brake Fluid by the Pint

If you’re in charge of ordering the supplies for your shop, volume discounts are great when they come along. Sniff them out where you can. But brake fluid is different! Buy it in bulk, but buy it in the smallest containers you can get away with. The reason? Brake...

Six Ways to Best Protect Yourself from Keyless Car Theft (For Now)

In 2023, a record number of vehicles were stolen in the United States; 1,020,729 vehicles to be exact. While that number has declined over the past couple of years (850,708 in 2024 and 659,880 in 2025), car thieves haven’t given up. In fact, they’re finding more...

Don’t Forget to Season the Automobiles, Mechanics!

I guess after you watch the following video, you won’t need much commentary. I thought this was common knowledge, but as I’ll explain in a moment, I may be wrong.I thought it necessary because a good friend at an independent repair facility recently bemoaned the fact...

Coolant Service – ASE Practice Question (VIDEO)

Description Technician A and Technician B are discussing proper cooling system maintenance. Technician A says that time and mileage should be considered but are not the only factors to consider when recommending a cooling system service to a customer. Technician B...

What are Frits? (And Why Does Almost Every Car Have Them?)

It’s a pretty safe bet that most younger techs haven’t heard of frits before. Not one single customer, ever, has come into your shop looking for some help with a frit problem. So while this article won’t help you turn bays faster or improve your diagnostic skills,...

Cat DTC Diagnosis (P0420) – ASE Practice Question (VIDEO)

Description Technician A and Technician B are discussing the troubleshooting procedure for a P0420 (Catalyst Efficiency Below Threshold) DTC. Technician A says that the presence of any other codes should be considered first before replacing the converter. Technician B...

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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