Intoxilyzer Won't Turn On, Won't Stay On, or Won't Hold the Date

Start here: which problem do you actually have?

"The unit is dead" covers three different faults with three different answers. Sorting yours before you do anything else saves a shipment.

• Won't turn on at all. Nothing on the display, no lights. Almost always the AA batteries or their contacts — and usually fixable where you are.
• Turns on but won't stay on, or drops power partway through registering a donor. Usually the battery pack's seating or connection rather than the cells themselves.
• Runs fine but loses the date and time between uses, or shows a message about an internal battery. This is a different battery than the ones you change, and it is not a user-replaceable part.

Safety first: batteries that get hot

If batteries in the instrument become hot, swell, leak, or show any sign of melting, stop immediately. Remove them if you can do so safely, put the unit somewhere it can't ignite anything, and don't install another set to "test" it. We have seen this in the field, and it means the instrument needs service — not another set of batteries.

The most common preventable cause is the wrong battery chemistry. CMI's Operator's Guide is explicit on this point: use only alkaline batteries. Rechargeables and lithium AAs are not equivalent in a five-cell pack, and substituting them is not a shortcut worth taking on an instrument your DOT program depends on.

Won't turn on at all

The Intoxilyzer 240 and 240D run on five AA batteries in a pack on the back of the unit. Work through these in order.

1. Fit a full set of fresh alkaline batteries. All five, all new, all the same brand and age. Mixing a fresh cell with four tired ones is a common cause of odd behavior that looks like a hardware fault.
2. Look inside the battery compartment before you install them. This is the single most common thing we find on a dead unit: corrosion. White or greenish crust, powder, or dark staining on the contacts means current isn't reaching the instrument no matter how new the batteries are. If you see active leakage, don't touch it with bare hands.
3. Confirm the pack is seated. Slide the compartment back on until it clicks into place. A pack sitting a millimeter proud will read as a completely dead instrument.
4. Press the On/Off switch gently. The manual makes a point of this — excessive force isn't required and doesn't help. A switch that needs to be mashed is itself a fault worth reporting.

If a full set of fresh alkalines in a clean, properly seated compartment produces nothing at all, the unit needs service.

Turns on but won't stay on

An instrument that powers up and then cuts out — particularly at a predictable moment, like when you start registering a donor — is usually not out of charge. Drawing more current is what exposes a marginal connection.

Check the same things as above, with attention to the pack's connector and its seating rather than the cells. Then note the pattern precisely: at switch-on, when registering the donor, during the blow, or at print. Where it drops out tells us a great deal, and it is the detail most often missing when a unit arrives.

Two messages are normal rather than faults, and worth knowing so you don't chase them. The instrument displays "Battery Low" when the batteries are nearing depletion, and a "Change Battery" message when a change is actually required — after which the unit powers itself off automatically. That shutdown is designed behavior, not a failure. Change the batteries as soon as possible after the first warning rather than waiting for the second.

The internal battery, and the habit that kills it

Separate from the AA batteries you change, the instrument has an internal lithium battery that backs up its computer circuitry. You do not replace this one; it is a service item. Its usual symptom is a unit that runs perfectly but won't hold the date and time between uses, or that reports an internal battery problem.

Here is the part worth internalizing, because it is the most preventable failure in this whole guide. CMI's guidance is to store the instrument either with batteries installed or with a power pack attached, precisely to avoid discharging that internal lithium battery. The common practice of pulling the AAs out before putting a unit away for the season does the opposite of protecting it — with no cells installed, the backup battery carries the load alone and drains.

What that costs you compounds. First the clock stops holding. Left long enough, loss of backed-up memory is also how calibration data goes missing, which the instrument reports as an E1 exception message — the code that means calibration data was lost and the configuration has reset to factory defaults. A unit stored empty over a long off-season can come back needing a full recalibration and setup rather than a set of batteries.

If you store instruments between testing seasons, store them with fresh alkalines installed, and note the date so the next person knows how old the cells are.

The printer is its own power system

If the instrument runs but the printer does nothing, that is a separate problem — the printer has its own rechargeable battery and its own charger. Confirm the printer is charged and switched on before concluding the instrument is at fault. Symptoms confined entirely to printing are covered in our printer troubleshooting guide.

What not to do

Don't open the instrument to attempt a repair. CMI states this directly in the Operator's Guide, and on an evidential breath tester it carries more weight than on ordinary equipment: an opened instrument raises questions about the integrity of every result it produces afterward. Battery compartment access is expected and fine. Anything past that is service work.

When to call us

• Batteries that get hot, swell, leak, or melt — stop using the unit and call.
• Corrosion in the battery compartment, especially if contacts look pitted or discolored after cleaning.
• No response at all with a fresh, full set of alkalines correctly seated.
• Power dropping at a repeatable point, such as during donor registration.
• Date and time not holding, or any internal battery message — this one needs service by design.

Call the office at 513-891-0868 with the serial number, and tell us exactly when the power drops. On an aging 240 or 240D it is also worth reading our guide on repairing versus replacing an aging breath tester before committing to a repair.