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Frequently Asked Questions

This FAQ page covers specific issues of the M216/ M500/ M700/ M900 Series of Thermometers as well as General and Repair Information. Use the subsequent links to skip directly to your particular model or for general/repair information.

For other questions, including anything not addressed below, please call (800) 346-1182 or email us at and a technician will be glad to answer your questions.

General Information
When was your thermometer manufactured?

M211 Thermometers:
1973 thru 1977
M212 Thermometers: 1977 thru 1979
M216 Thermometers: 1979 thru 1995
M500 Series thermometers: 1995 thru 2005
M700 Series Thermometers: 2005 thru 2017
M900 Series Thermometers: 2017 thru present

Can my probe be repaired?
There is a good possibility that we can repair your probe if it is damaged. It is almost always worth sending the probe in to be evaluated. We do not charge for estimates.

What do repairs cost?
Our basic service charge is $69.00. This will include an operation & calibration check. Parts are extra. We do not charge for estimates, and will gladly provide you with one before we perform any service, if you request an estimate.

Where do I send repairs & what information do I need?
Send your repairs to: GLA Agricultural Electronics Attn: Repair Department
3563 Sueldo Suite D
San Luis Obispo, CA 93401-7300
Please include: Thermometer / Probe / Charger
A detailed note describing the problem
A return shipping address
A billing address, and
A phone number to call with questions

How to reach us?
(805) 541-3758
(800) 346

How do I pay for repairs or new products?
GLA does accept Visa / MasterCard / American Express / Discover. 

What products have a warranty?
M900 Thermometers: Two (2) years from date of purchase
M207 Probes / One (1) year from date of purchase
C965 Chargers / Ninety (90) day
s from date of purchase
C725 Cha
rgers /Ninety (90) days from date of purchase
B601 Battery Pack /One (1) year from date of purchase

Can you explain the difference in C316 Chargers vs. C725 Chargers?
The C316 Charger is designed to work on the GLA M212 Series Thermometer and the M216 Series Thermometers. When a C316 charger is attached to either a M212 or M216 Thermometer you will see a (-) minus sign indicated on the left side of your LED Display. The C316 Charger will work on a M500HPDT Thermometer if necessary; however, it is not designed to power it properly. You may find that your battery does not take a full charge with a C316 when used on a M500HPDT. If you attach a C725 to your M212 or M216 Thermometer, you will NOT see a (-) minus sign indicating a charge. A C316 Charger will not work on the M700 Series Thermometers.

Is the C725 Charger designed to work on the M500HPDT and M700 Series of Thermometers?
A C316 Charger will NOT work on a M700 / M750 Thermometer. The LED screen will read Err2 indicating a low battery. A C316 does NOT have the correct output for a M700 Series Thermometer. Also you may notice when you take your M500HPDT Thermometer off charge, with the C725 Charger attached, the decimal points continue to appear on the screen. This is normal and is a function of the charger; they will stop after a few moments.

What happens if my thermometer gets wet?
Should your thermometer become wet inside, carefully remove the bottom four screws and bottom plate, (trying not to damage the bottom gasket). Next remove the six window screws (note: they are different sizes than the bottom screws), gently push the window down, firmly grasp the bezel of the unit and slide it out of the box. Let any water in the unit drain out and allow the unit to dry overnight in a warm dry location. You may also use compressed air to dry the unit. Carefully reassemble the unit in the reverse order of disassembly and your thermometer may continue to work properly if the water damage has not been too severe. If your thermometer does not work after these steps, please return your thermometer to GLA. NO OTHER DISASSEMBLY SHOULD BE ATTEMPTED. DUE TO THE MICROPROCESSOR OPERATION, IT IS IMPORTANT THAT ANY FURTHER REPAIR BE DONE ONLY BY A QUALIFIED ELECTRONICS TECHNICIAN, PREFERABLY A GLA REPAIR TECHNICIAN.

Why is my display screen only showing a partial number, or only partially lit?
This is usually the result of two problems. The unit may have gotten wet and there is a corrosion problem on the circuit board itself. The more common problem is that the thermometer has been dropped hard and the LED’s have come out of their retaining sockets. If this may be the case, loosen the six window screws; gently push down evenly on the window, pushing the LED’s back into place. Re-tighten the window screws, finger tight only and this should solve your problem. If it does not, you will need to send your thermometer to GLA for service.
M900 / M950 Series of Thermometers

I don’t see the charging indictor on the screen?
Turn the unit on, the charging indicator is only visible if the unit is on.

What does “Inside Temperature” mean?
The internal temperature is a diagnostic tool for GLA Technicians.

What does “Cal Number” mean?
This is a diagnostic tool for GLA Technicians.

What if my M900/ 950 shows “Not passed”?
  • A very discharged battery will show this message
  • If your probe is damaged it will show this message
  • The internal temperature is too hot.
  • If the calibration is out of tolerance due to water or corrosion damage

Why does my M900/M950 read “Probe Error Please Try Another Probe” if my probe is attached?
This indicates that probe is damaged and your thermometer is not reading the probe.

Do you offer a car charger?
No, but they are available, your thermometer requires the following specs – micro USB port, Input 100-240v 50/60Hz 0.18a Output 5.0v 1.0a

My battery does not show 100% even after charging overnight?
Due to the battery discharge rate and software designed to prevent overcharging, you may never see 100% even though the battery is fully charged.

Can I replace the battery in the M900/M950?
No, the lithium Ion battery has a propriety connector and must be replaced by a GLA technician.

Why is my screen completely blank?
External temperature, either too hot or too cold can cause the LCD screen to go blank. To solve this, please bring the M900/M950 to normal operating temperatures.

Can I open my M900/M950?
There are no user serviceable parts inside the M900/M950. Accessing the interior of the thermometer may void warranty.

How do I save a temperature in the M900?
When the desired temperature is reach, press the Save/Select button (Orange). This will save the temperature to your SAVED TEMPS Screen.

How do I clear the saved temperatures on my SAVED TEMPS screen?
You can store up to eight (8) temperatures in your M900. Saving the 9th (9) temperature will overwrite the oldest temperature.

How do I switch between “CONT” and “PEAK” temperature?
Press Mode/Scroll (Green) Button.
My LCD Display is scrambled and will not change.
Your M900 requires a hard reset. Please press and hold the Yellow Light button for five seconds. This will reset your thermometer to the correct operating mode.

My LCD display is blank and only the back light is operating.
Your M900 requires a hard reset. Please press and hold the Yellow Light button for five seconds. This will reset your thermometer to the correct operating mode.
Does the M950 come with a software program?
No. The M950 comes with a driver, allowing use of a Terminal Emulation Program for output. We recommend YAT 2.0 (Yet Another Terminal). It’s a free program you can securely download via SourceForge:
M900 / M950
M700 / M750 Series of Thermometers
My M700 / M750 does not turn ON when I push the button. How do I turn it on?
Unlike previous GLA Thermometers (M211 / M212 / M216 / M500 Series) the push button does not power the unit. The Control Knob is the power switch.

Why does my M700 / M750 read Err1 on the display?
Err1 in Position I or Position II indicates that you either do not have a probe attached to your thermometer, or that you have a damaged or shorted probe. To correct this reading, either attach a M207 Probe or replace your damaged probe. It is often worth your time to remove your probe and look at the “prongs” on the probe connector itself. If the probe has been over tightened onto the thermometer, the prongs often do not make proper contact with the thermometer’s probe connector. Gently spread the prongs out, this may solve the problem.

Why does my M700 / M750 read Err2 on the display?
Err2 indicates a low battery charge. This will be shown on your LED display. This will normally happen when your battery is discharged to 5.5 volts. To correct this, please charge your thermometer. It may take up to a minute of charging before you see any charger indicator lights.

Why is there no display on my M700 / M750?
If there is no display, turn the Control Knob to Position I. If you still do not have a display, attach the charger unit and plug it into a wall outlet. If the charging lights appear, allow it to charge fully. If the battery will not hold a charge and the charger appears to be working (indicated by the rotating LED segments), the battery is probably in need of replacement.

If there is no display when you attach the charger, please check your charger. Does it appear to be melted or is it hot to the touch when plugged into the wall? If so, you will need to replace your charger.

Why does my M700 / M750 not read 100.0(F) or 37.8(C) when I check calibration in Position 0?
If your probe is attached, the M700/ M750 will NOT read 100.0(F) or 37.8(C); the number on the display is irrelevant and means nothing. Another probe may give you a completely different reading. Remove your probe and check calibration again. If your probe is not attached and it reads -40.5 on your display – your calibration check position is damaged and can be repaired, please send your M700/M750 in for repair. If you have any other reading than 100.0(F), 37.8(C) or -40.5, you have a damaged M700/M750; you must return it to GLA for repair.

Will my M700 / M750 read below freezing?
Yes, the M700/M750 Thermometer will read below freezing, however we cannot and do not guarantee the accuracy of the M700/M750 outside of the temperature range of 80° -120° Fahrenheit / 30° – 50° Celsius.

When I turn my M700 / M750 off, why does the display not always read OFF?
If you rapidly turn the M700/M750 ON or OFF, your display may not read OFF. The M700 requires that a temperature is “sensed” by the probe before the unit may read OFF. As long as the screen is blank, your unit is OFF.

Why does my M750 display shows FULL?
If FULL appears on your screen in either CO (I) or PH (II) mode, it indicates the memory is full in the thermometer and you must clear the memory of the M750 to continue to store additional information. To clear the memory, you must clear it through the menu steps when the M750 is connected to your computer.

Which terminal emulation program should I use with my M750?
We strongly suggest that you use a program called Tera Term which you can download at: Or you may use HyperTerminal which can be found as a program on Microsoft® Windows®

What is the reason that my M750 has reset the date to 01/01/1970 and the clock to 00.00.00?
This is usually caused by a completely dead battery or a software problem. You may reset your date and time via the menu options. If this occurs ID’s and temperature should not be lost as they are stored in EPROM rather than the processing chip. Please check your log.
M700 / M750
M500 / M525 / M550 Series of Thermometers
Why does my M500 Thermometer reads PrbE Err!?
PrbE Err! reading is shown when your M500 Series Thermometer can’t locate a signal from the probe. This can be due to your probe being damaged. If the probe does not appear damaged or broken, turn the unit on with the probe attached, pull & stretch the cord. Does this cause the display to fluctuate? If it does, it may indicate a damaged cord. If you have a spare probe available, put that probe on your thermometer, does it work properly now? If so, the problem is with your probe. You may also want to check the probe connector on the thermometer box, is it tight & secure? (If it is not secure – DO NOT open the unit from the top, call us and a technician will help you). You may also receive a reading of PrbE ERR!, if the ambient air temperature is below freezing. Inserting the probe into the animal will most likely correct this reading. Another place to check is the connector on the probe itself. Often when a probe is over-tightened, the “prongs”in the connector may need to be spread apart to make a proper connection. Look at the connector, and gently pry the prongs out, this may solve your PrbE ERR! reading.

Why is my M500 Thermometer not reading accurately?
You will probably need to contact GLA directly for this answer. We will ask you the following questions: Why do you think it is inaccurate? How is it operating differently than previous use? Please have the thermometer accessible when you call. We will most likely ask very specific questions, and it helps to have the thermometer available.

Why does my M500 Thermometer seem to be reading in Celsius?
Your M500 has been switched from Fahrenheit to Celsius. To switch it back to Fahrenheit, please follow these instructions: Put the Selector switch in the INST position, PRESS and HOLD your ON switch / Wait for the display to go blank, still holding down the ON switch / Then turn the Selector switch to the HOLD Position / The GLA initial display will appear, then the display will read SET, let go of the ON switch. / The Display will then read CELC / Putting the Selector switch back to the INST position selects Fahrenheit (FAHR) / Putting the Selector switch in the HOLD position selects Celsius (CELC) / Select temperature scale / PUSH the power switch, DONE will appear on the LED display / the unit is now in the temperature scale you selected.

Why does my M500 Thermometer always reads the same temperature?
You may have your M500 in the HOLD position. To reset the temperature simply depress the power switch once.
M500 / M525 / M550
M216 Series of Thermometers
Why does my M216 Thermometer reads OFL?
First, check to see which switch position your M216 is in. Is it the temperaturing position (green/left position)? Does the OFL reading change when you remove the probe? If it does, you most likely have a damaged probe. If the unit reads OFL in all positions, it usually indicates the unit may have gotten wet, or one of the IC’s has failed. In either case, you need to send the thermometer to the factory for repair.

Why does my M216 Thermometer reads the same in the temperaturing position as my battery check position?
If your M216 Thermometer is reading the same in both the far right & far left position this is an indication that your thermometer is not reading the probe. Check to make sure your probe is working properly or that the connector on your thermometer is tight.

Why will my M216 not stabilize; the display is running up or down?
If your M216 is; rapidly running numbers across the display, first check and see if it does this only in the green/temperaturing position. If it is just in the green position, it is most likely your cord. If you stretch the cord, you should notice a change. If it is running in two or more positions, the unit has probably gotten wet inside. You may remove the BOTTOM PLATE ONLY to check for moisture. If it is wet, allow it to dry overnight before replacing the bottom plate. Please be very careful not to damage the gasket on the bottom plate.

Why does my M216 Thermometer comes on, and then fades out?
Your thermometer is not charged. Please attach the charger and charge the unit overnight. If you have just done this and you had the charging indicator light come on when you hooked it up to the charger small dash (- sign) on the left of the display, then you most likely need a new battery pack. If you do not see the charging light, you may need a new charger. Please note only a C316 Charger will light the (-) on your M216. Please see the FAQ on chargers.

Why won’t my thermometer hold a charge?
Are you getting charging indication lights? Charging of M216/M212 Thermometers is indicated by a small dash or “-” sign on the left side of the display when the charger is attached and plugged in And using a C316 Charger. Scrolling decimal points running from left to right across the bottom of the display indicates M500 Series Thermometers, charging. A rotating or single lit LED segment, or the far right decimal point lit, indicates charging on the M700 Series Thermometers. If you do not see these charging indicators, you should check your charger for correct operation.

Can my thermometer be calibrated?
GLA Thermometers are calibrated at the factory; there is no calibration that can be performed by the consumer. M216 Thermometers may be slightly out of calibration if the battery is very discharged. M500HPDT Thermometers can only be checked for calibration at the factory. M700 Thermometers can be checked for calibration by using your calibration check position. Severe water or moisture damage will affect calibration of any GLA thermometer. If you doubt the accuracy of a GLA Thermometer, the first place to check is the probe for damage. Often inaccurate temperatures are caused by a damaged probe.
If you are experiencing problems not discussed here, or you need further information,
please call us at (800) 346-1182
or email us at
and a technician will be glad to answer your questions.

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