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May 20, 2025

KB - Comark Handheld Thermometers including Bluetooth and KM20REF Technical Support

Handheld Thermometers including Bluetooth and KM20REF Technical Support

Comark has a number of different Handheld Thermometers for multiple applications but the process to go through for each one before deciding if you need to return it is basically the same for each one.

Items to check before returning for Service

Before considering returning your Handheld Thermometer for Service make sure that the battery has been checked and is in good condition. When replacing the battery be careful not to over tighten the battery screws as this can lead to the case cracking.

Note – In the case of the N9094 and N9005 these both have a 10 year non-customer replaceable battery and therefore if the battery fails you have to return the Thermometer for battery replacement. Please contact Comark UK Service before returning your N9000 Thermometer to check that we can replace your battery.

Troubleshooting

Please check this list for your model or similar. If your model is not listed please contact your Local Distributor or Reseller or Comark Direct for more information or search for the particular model on the Comark Instruments Website. If the Thermometer is not listed here or on the Comark website then it is likely that it has been out of production for some years and therefore we may not be able to repair it.

For two pronged Thermocouple Thermometers you can if you do not have another probe to hand, use a Paper Clip to short out the probe input to record an ambient reading on the LCD of the Thermometer. This will generally confirm that the probe is the issue not the Thermometer and therefore you just need to replace the Probe which are generally considered disposable and not replaceable. Please Click Here for Technical Support on Probes.

KM221 / DT15

Once the battery has been replaced if the Temperature is not displayed then the probe is probably at fault. Unfortunately we no longer carry spares of the probe and therefore replacement will be of both the Thermometer and the Probe. The KM221 / DT15 is generally considered as disposable when it comes to repair due to it’s low cost so you may want to consider just replacing it rather than returning it. Please however recycle responsibly.

Note that the older KM220 is no longer available for Service repair.

Click Here to visit the KM221 Page (ROW)

Click Here to visit the DT15 Page (USA Only)

KM20REF

The KM20REF Reference Thermometer should be returned to a Calibration House Annually for checking and if required adjustment to the Calibration. As soon as the Low Battery warning is displayed the Battery should be changed with a new Alkaline Battery as the readings may not be accurate. Always keep the KM20REF in its protective case.

In the UK you can return the KM20REF to our UKAS Laboratory in Norwich for Annual Calibration, please click here and follow the instructions.

Click Here to visit the KM20REF Page

DT33

The DT33 Water Resistant Digital Thermometer is a compact hand-held unit with a range of interchangeable probes available. Troubleshooting includes checking that the probe is not faulty and confirming that the battery is good.

Click Here to visit the DT33 Page (USA only)

C42C/F, C46 and C48C/F Models (For C22 and C28 the Troubleshooting is similar)

When diagnosing the C20 or C40 Series thermometers the faults can include ‘- – – -‘ which is usually the probe or ‘OPEn’ which means that the battery cover is not fitted or not tightened down. Check the alignment of the Battery Cover and the 'pip' on the battery cover which can get worn or damaged over time causing this to fail. In this case the Thermometer may need to be replaced.

If the case gets damaged water ingress can occur which can lead to the instrument not working and misuse of the keypad (operation with the probe tip) can cause the keypad to fail.

The older C20 series models can no longer be serviced and if you choose to return these for repair you will be offered the equivalent C40 Series Instruments instead.

Click Here to visit the C42 Page (ROW Only)

Click Here to visit the C42F Page (USA Only)

Click Here to visit the C46 Page (ROW Only)

Click Here to visit the C48 Page (ROW Only)

Click Here to visit the C48 Page (USA Only)

Bluetooth BT42C/F and BT48C/F

Faults as per C42 plus the Bluetooth can fail occasionally. If your Bluetooth Unit fails to connect to your App please remove the battery and wait for 1 minute before re-fitting and trying again. If this fails to resolve the issue then return for investigation and repair.

Click Here to visit the BT42 Page (ROW Only)

Click Here to visit the BT42 Page (USA Only)

Click Here to visit the BT48 Page (ROW Only)

Click Here to visit the BT48 Page (USA Only)

Comark Bluetooth API

The Comark APIs enable a User Interface (App) to extract data such as temperature and humidity from the Pocketherm Bluetooth Thermometer and have it sent to the User Interface (App) to be displayed as results. The benefit of this approach is that you can bring large amounts of HACCP critical data from various devices, into a single platform, using a third-party program or software suite. This enables you to monitor manual tasks from product delivery to food storage, food preparation and foodservice. You can also incorporate real-time monitoring data for periodic checks of your storage and display units, thus freeing up valuable staff time to concentrate on more operational and quality tasks.

In order to use the Comark API’s you will of course need a User Interface (App) or Software Suite. Please Click Here to download a copy. 

KM330 / KM340

The KM330 and KM340 have few faults. ‘OL’ on the LCD just means open circuit probe so please check that your probe is OK before returning. You can test the probe by removing it slightly from the connector and shorting out the two pins using a paper clip. In this case the Thermometer will read ambient temperature to indicate that the Thermometer is reading OK.

Click Here to visit the KM330 Page

Click Here to visit the KM340 Page

N9005

Industrial Thermometer Sealed for Life 10 Year Battery which can be replaced by Service.  When diagnosing the N9005 Thermometers the faults can include ‘- - - -‘ which is usually the probe. Test the probe by shorting out the inputs to the Thermometer with a paperclip and the Thermometer will read ambient if all is well. If the keypad becomes damage due to misuse with the probe then water ingress into the Thermometer is possible and this will damage the Thermometer leading to premature failure, but it is often hard to check for keypad failure as the damage can be difficult to see.

Click Here to visit the N9005 Page

N9094

Food Thermometer, Sealed for Life 10 Year Battery which can be replaced by Service. If the Thermometer is not displaying temperature please try another probe to check that it is not the probe that is at fault.

Click Here to visit the N9094 Page

KM28 and KM28B

The ‘OL’ message will appear if your KM28/KM28B Thermocouple Food Thermometer is turned on without a Probe connected via the device’s sub-miniature connection. If a suitable probe has been connected via the sub-miniature connection on the front of the device and the ‘OL’ error is still being displayed, then this can indicate a fault with the connected probe. In this instance we would recommend that the probe in question is disconnected from the device and a new or alternate probe is connected instead. Should the ‘OL’ error message persist, despite alternate probes being connected and tried, then the Thermometer(s) in question will need to be returned to our Service Department for repair.

Click Here to visit the KM28 Page (ROW)

Click Here to visit the KM28 Page (USA Only)

Pocketherm – P125 / P250

The Pocketherm Folding Thermometer can suffer with issues surrounding the swivel which can cause switch failure in early models. This was revised in later models. In addition the probe can go open circuit, ‘- – – -‘ on the LCD.

However, all models are now retired and Fluke no longer has any stock to repair these. Please accept our apologies.

Click Here to visit the P125 Page (ROW)

Click Here to visit the P125/82 Page (ROW)

Click Here to visit the P250F Page (USA Only)

Click Here to visit the P250FW Page (USA Only)

My Thermometer is not Listed

If your Thermometer is not listed above then it is likely that it is no longer manufactured or discontinued by Comark/Fluke or has been recently retired. In that case please use the above list to find something similar in the list as the Troubleshooting items are often very similar for recently discontinued items. For example, C22 and models in the C2X series model range have the same case design as the C4X series and therefore the troubleshooting items are very similar. Likewise older variants of the N9000 and N1000 range which all used the same case design. We no longer stock spares for older versions of the C2X series thermometers so if you return one of these for repair you will be offered the equivalent C4X series as a replacement.

Warranty

If you are claiming warranty for any product returned to Fluke Service please ensure that you include all the necessary proof of purchase.

My Product is Obsolete on the Website
If your product is obsolete on the Comark website do not worry we may still be able to offer support for it. Please continue to the section below Returning an Item for Repair or contact our service department on Comark UK Service for advice on whether we can repair your item.

Returning a Thermometer for Repair or Replacement (Or UKAS Calibration UK Only)

To return your Thermometer for repair or replacement is straightforward but please note the cost of returning it may out way the cost of the Thermometer and that it might be more cost effective to replace. Please take this into account before looking to return your Thermometer to us especially for out of warranty repairs.

Please select the most appropriate link below.....

UK / EU Customers - For customers in the UK and some EU Customers please Click Here to return product directly to our Service Centre in the UK. Please note this facility is only available to customers in the UK and EU.

USA Customers - For customers in the USA please Click Here to return product directly to out Service Centre in the USA. Please note this facility is only available to customers in the USA.

ROW Customers - For the ROW Customers your best option is to contact one of our Resellers/Distributors who can advise the best way to get the Instrument back to us for repair. This can be the one who sold you the Instrument or just one that serves your local region. Please Click Here to use our 'Where-to-Buy' section on the Comark Website to find a local Distributor/Reseller near you who will be able to assist you.

Contact Technical Support

If you still don’t find what you need here please contact Comark Instruments for additional support detailing the issue you have on the following e-mail Comark Tech Support and we’ll get back to you as soon as we can.