Deciding Whether to Repair or Replace an Aging Breath Tester

What's happening

Evidential breath testers are built to last years, and most of the time a fault is a straightforward repair. But like any instrument with mechanical and electronic parts — a sampling motor, a fuel cell, a circuit board — there's a point where age catches up with it. Older units can run into a specific problem: the manufacturer stops stocking replacement parts for models past a certain age, so a repair that would otherwise be routine isn't possible anymore. This guide walks through how to recognize that situation and think through the repair-versus-replace decision.

What a failed component actually means

A few different internal failures can all lead to the same outcome — a unit that can't be brought back into working order:

• Fuel cell that won't take calibration. The fuel cell is what actually measures alcohol concentration. If a new fuel cell is installed and the unit still won't calibrate against a known standard, the fuel cell isn't the whole story — something further down the sampling path is also out of spec.
• Sampling motor running below spec. The motor drives the air sample through the instrument at a controlled rate. A motor running slow throws off every reading downstream of it, and on older units, a replacement motor may not be available from the manufacturer at all.
• Sampling board failure. A failed sampling board can present a few different ways at the operator level — including the air-blank-won't-clear symptom covered in our air blank guide — and, like the motor, may not have an available replacement part on an older unit.

Any one of these needing replacement is routine on a newer unit. The complicating factor is age: manufacturers generally stop stocking parts for units built many years earlier, and once an older unit needs a part that's no longer available, it can't be brought back into service through a normal repair.

How to think about repair vs. replace

1. Send the unit in for evaluation before assuming either outcome. Age alone doesn't mean a unit is unrepairable — many older units still repair normally. The only way to know is to have the specific failed component evaluated.
2. If parts are available, it's a normal repair. The standard process: replace the failed part, run the instrument through its full calibration checks, and ship it back in service.
3. If parts aren't available, weigh replacement. At that point continued use of the unit isn't an option regardless of cost, so the practical question becomes timing and budget for a replacement rather than whether to repair the old one.
4. Factor in how the unit fits your program going forward, not just the immediate fault. A unit that's already had one major component fail is more likely to need another before long. If you're weighing a marginal repair against replacement on a unit that's been in service a long time, it's worth asking us what we're seeing on similar units of that age before deciding.

We won't promise a repair outcome or a turnaround time before we've actually had the unit on the bench — age and visible symptoms narrow down what's likely, but the evaluation is what confirms it.

Documentation for your DOT program

If a unit is retired or replaced, keep your program's paperwork consistent with what 49 CFR Part 40 expects of your evidential breath testing devices and your written procedures. A few things worth having on file:

• Records of the unit's calibration history up to the point it was taken out of service.
• Documentation of when and why a device was retired — for your own program records, not something we file on your behalf.
• Confirmation of the replacement device's initial calibration once it's in service, so there's a clean record of the transition.

Foster doesn't determine your program's compliance status — that's between your organization and your DOT-mandated procedures. We're glad to provide calibration and repair records for anything we've serviced to support your own documentation.

When to call us

• You want an evaluation before deciding whether a fault is repairable.
• You're weighing repair against replacement on an older unit and want to know what we're seeing on similar units.
• You need calibration or repair history for your program's records.

Call (513) 891-0868 or email service@fosterinstruments.com.