Accurate refrigerator thermometer?

The past week my Kenmore refrigerator freezer has been running about 15 over 0. It used to be 0 or a bit less on the Walmart freezer thermo. I tried another Walmart thermo that measures both refrig and freezer. Same reading. Called extended warranty service guy. His (expensive?) thermo read -5. He says freezer ok, my thermos bad. I had no grounds to argue with him about it.
So my question is, where can I get an accurate thermo a service guy will believe? Brand name? Source? Service guy says to buy from refig supplies co - he also says the only one in my city only sells to dealers, service guys, etc.
I also found out a previous service guy was wrong, my refrig does have cooling coils. They are in back at bottom-rear (not under) of refrig. He and I tried to pull refrig away from wall in it's little walled-off area but were unsuccessful. Any suggestions on how I (79 yrs old) can move it out to get at coils to clean them? Service guy suggested a leaf blower blowing under frig - says it will clear off rear coils. ???
TIA
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"Where there's smoke there's toast!" Anon






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Try to find a lab thermoter. High school would do.
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Not sure what that is, but when I measured lab equipment I had access to a few of my choice instruments. Radio shack $15 thermistor probe, fluke and triplet thermocouple probes. Fluke IR thermometer, as well as HF near field IR thermometer. Large mercury thermometer, I only used as a comparison.
Sometimes probes have to be right on top of each other, and stabilized, to get the same readings. Air flows can be deceiving. Even taking a reading of a beaker of water, needs high circulation to get equal readings. There is normally a high temperature differential of a still beaker of water.
Greg
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An IR Thermometer gives instant results and can be used for many other uses from catalytic converters to bad capacitors in a PC or TV. This was very handy I when I needed to test for a bad defrost heater. Often available for less than $20.

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On 12/9/2013 1:29 PM, John Keiser wrote:

Those point and read units are not accurate on shiny metal. Need to read the temp of the items in the freezer. Ice cubes, boxes of food, etc.
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Like anything else, one must shop carefully on eBay or Amazon. My unit seems very accurate when measured against ice and boiling water. I haven't thought if a standard for high temperature catalytic converters yet. :)
wrote:

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On 12/9/2013 3:46 PM, John Keiser wrote:

IR thermometers are notoriously inaccurate. They measure radiation, not temperature. Different surfaces have different emissivities. They give different readings for the same temperature. More expensive ones have adjustments for emissivity, you just have to know the exact number for that exact surface...
Another little-appreciated fact is that cheap ones have a wide field of view. Unless the item fills the field of view, you can't count on the numbers.
If you wanna measure the temperature in the fridge for cheap, go get a liquid thermometer. Those graduated on the glass are likely more accurate than those that can move against a calibrated holder.
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Ken,
freezer has been running about 15

It's really, really hard to believe that your thermometer suddenly failed unless you whacked it. Yours reads 15 deg and his reads -5? That's 20 deg. Something is most strange. Take your thermometer out of the fridge and park it near a room thermometer for half an hour. Is it 20 deg off? Any cheap fridge/freezor thermometer should be NSF intl certified. That means it's food safe and fairly accurate.

See above.

Ok, let's move the fridge. It's in an alcove and is glued down by years of kitchen crud. Turn off the fridge using the temp control inside the fridge. With the fridge door open look for and remove the bottom trim panel, often look like vents. With the trim off and the fridge door closed you should see the 2 front supports they should look like big bolts with rubber feet. Get a pry bar and a fulcrum. Find a spot near a foot and on the metal frame of the fridge. Pry there. We want to lift the fridge. Now do the other foot. This should "unglue" the front feet. Now carefully push the top of the fridge into the alcove. Then out. We want to rock the fridge to free up the 2 back feet. When all of the feet are free you should be able to rock the fridge from side to side and "walk" it out of the alcove. Now, unplug the fridge and vacuum the coils under and in back of the fridge. Get a mop and swab out the alcove floor. Plug the fridge back in. Walk the fridge back into the alcove. Open the door and reattach the bottom trim panel. Set the temp control and close the door.
Dave M.
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He may have been reading the C scale instead of the F scale. the -5 C is about 23 F.
To check the thermometer you can get a glass and put some ice and water in it. Stir it for a while and put in the thermometer. It should show 32 deg F or 0 deg C. Just don't have the thermometer on the ice ore side of the glass, but in the water.
If your old thermometer changed that much and another one agrees with it, looks like the service man may be wrong. Next time get him to try the ice water test.
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On 12/9/13, 11:17 AM, Ralph Mowery wrote:

Agreed.
Also, refrigerator & freezer temps continuously 'bounce' up and down all the time caused compressor cycling, defrost cycles, and door opening events.
It's the 'average' temperature that's important.
For the refrigerator side, put your thermometer in a glass of water; one where you can read it while still submerged. It's amazing how quickly some thermometers can react to room temperature air if pulled out for reading. Give it a day to normalize, then take and average multiple readings over a few days.
Same dance with the freezer, but sandwich the thermometer between something like bags of frozen vegetables, and read with the sensing bulb still sandwiched.
For the record, I've had pretty good luck with those bi-metallic analog refrigerator/freezer thermometers. Their 'capsule' isn't vented, so they retain an accurate reading for a short period. They can also be quickly/easily read in place... and I'm now in the habit of checking them every door opening
I've heard the best temps for maximizing food storage time with minimal energy use is 40°F in the refrigerator, and 0°F for the freezer.
As I recall, most if not all of the above is in my refrigerator owners manual... check yours, it's likely there as well.
Good luck!
Erik
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Looks like you tried two thermometers good show. Where it was placed and time of day might alter readings.
If you want to be safe, use one thermometer that measures closely to one or two others. I also often use an IR thermometer to verify another reading. Thermometers can drift off, or be off. Just know what Is what.
I don't have access to it anymore, but I used to also use a data logger to track 24 hours.
Greg
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Rent an air sled. Easy as pie.
Service guy suggested a leaf blower

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What's an air sled? Sounds better than my little hand truck.

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"Where there's smoke there's toast!" Anon






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I've found mercury thermometers are all over the place at freezer temperatures. 10C errors are easy to have. I put the unkown thermometer in a known good freezer running at -18C and mark the mercury level with a marker pen, then use it to check my unknown freezer temperature.
Even allegedly accurate thermocouple thermometers on a digital multimeter can be all over the place at -18C.
Having said that I do have some cheap mercury thermometers that do actually read correctly at -18C. Otoh I have two quite expensive refrigerator mercury thermometers that read fine at refrigerator temperatures, but are both quite wrong at freezer temperatures.
My experience is that it isn't easy to read freezer temperatures accurately. Even allergedly identical mercury thermometers can differ by 5C. (I've tried 30 or 40 mercury thermometers out btw.) Ditto bimetal strip thermometers.
Yeah, I know. It surprised me too!
Btw it makes quite a difference to freezer running cost if it is running too cold. 10C too cold is the same as making it 10C hotter ambient temperature. It can boost the daily running cost by 50%.
Ross
Ross
Ross
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In order for it to be a shield, the door would have to make electrical contact all the way around. Grounded hinge only, is an antenna.
Greg
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Bingo!
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