Marinucci: Spare fuses may result in happy customers

A spare fuse for a meter may mean the difference between a satisfied customer and a disgruntled one. Here’s the scoop.

For years, I have stressed the importance of meeting or exceeding motorists’ expectations at your tire dealership or service shop.

Typically, achieving these goals requires fixing the vehicle correctly the first time — not to mention repairing it on time. Obviously, there’s a long list of potential problems that may delay a job unexpectedly. 

I have reminded readers that savvy bosses evaluate their service departments, watching for ways to minimize the causes of delayed repairs. All too often, eliminating these problems requires awareness and shrewdness, rather than sheer time and money. 

Stocking spare fuses for automotive test meters is a prime example of a practical, cost-effective precaution. By far, the most popular of these devices is the multipurpose digital meter.

I don’t want to overwhelm non-technicians with technical jargon, but at this point, it’s extremely helpful to understand three common electrical measurements. 

The first is voltage, which is electrical pressure measured in volts on a voltmeter. 

The second is current, which is electrical volume measured in amps on an ammeter. (No, contrary to what many people think, there’s no “p” in the word ammeter.) 

The third is resistance, which is measured in ohms on an ohmmeter. Resistance is anything that opposes the flow of current through a connection, component or circuit. 

There are popular, professional-grade digital test meters that measure — among other values — volts, amps and ohms. Note that this multi-function test meter may be known as a DVOM (Digital Volt-Ohm Meter) or DMM (Digital Multimeter).

Features vary from one commercial-grade automotive meter to another, but many of these devices measure amps as well as milliamps. (A milliamp is one-thousandth of an amp.) 

What’s more, the meter manufacturer often protects the current-measuring circuitry with one — possibly two — specialized fuses. These relatively small, ceramic-style fuses are designed to pop promptly if the user subjects the meter to excessive current.

For instance, suppose the meter has a 10-amp scale; it’s designed to measure no more than 10 amps. Next, imagine that a careless, harried technician connects the meter to a circuit that’s carrying more than 10 amps. 

Predictably, current greater than 10 amps will blow the meter’s fuse. The bottom line is that a tech may not be able to complete a proper diagnosis because the blown fuse has knocked out his meter’s amps-measurement channel.

Based on my shop experience, it’s not difficult for a hurried tech to misjudge the volume of current flowing through a circuit. After all, to err is human, isn’t it?

There’s an old joke that there’s no good time for tools and equipment to fail out in the bays. Whenever a meter fuse blows, it seems to happen on a diagnosis that’s running very late. 

Of course, repairing a vehicle on time is a dicey proposition — at best — whenever the diagnosis isn’t finished. 

Worse yet, this particular job may involve a car owned by one of your crankiest, most cantankerous customers.

Due to the overall trends in automotive design, electrical testing has become commonplace on service-age vehicles rolling into tire dealerships and service shops. Therefore, reliable meters are vitally important.

Remember that many DVOM and DMM products are not sold with spare fuses. Rather, it’s up to the user to worry about spares. 

The first practical precaution owners and managers should take is assessing the needs of their particular service department. Namely, inventory the DVOMs and DMMs in use and identify which fuse or fuses these meters have.

The fuse type may be printed on a label on the back of the meter — sometimes it’s molded right into the tool’s housing. 

Usually, the fuse type is called out in the maintenance section of the meter’s operating manual.

The second sensible precaution is investing in a set of spare fuses for every meter in the service department. A proper, fast-acting fuse for a professional meter may be in the range of $7 to $10 or so. 

For one thing, I consider meter fuses to be consumables akin to shop towels, solvents, etc. Buy them and write them off! 

For another, spare fuses are cheap insurance against a delayed or improper diagnosis. For instance, suppose a tech slips up and pops a fuse during testing. He may be too embarrassed to admit this mistake. Instead, he simply guesses at the correct diagnosis on that problem.

Last but not least, remember that the proper, fast-acting (“fast-blow”) fuse is a key safety feature of a DVOM or DMM. In fact, that specialized fuse is an integral part of the meter’s UL (Underwriters Laboratory) rating. 

Don’t scrimp by installing a cheap substitute for the OEM-style, fast-blow fuse.

In my next column, I’ll discuss simple, inexpensive ways to prevent fuse failure in the first place and cite some sources of the proper fuses.

Dan can be reached via e-mail at [email protected] His previous columns are available at www.tirebusiness.com.