Tip & How-To about Heating & Cooling

Understanding the display on the programmable Theremostat & the 24 volt control.

Hi, I have seen this over and over, some people asking about the display on there thermostat, and getting a reply that is not at all true. This goes for all Air Conditioning and Heating systems using the programmable thermostat. I would like you to keep this in mind.Every unit has a control transformer that supplies 24 volts to there thermostat. What I am seeing a lot of is, they are told that some units are controlled by the batteries in the thermostat. No, as the unit will not function properly if the batteries are weak or dead yes, but the batteries are used for the digital display that tells the unit when to come on and what comfort zone you want. If you loose the display on a residential A/C or Heater thermostat, change out the batteries to get it back, but keep in mind that you must also have 24 volts from the control transformer for you're system to operate. To sum it all up is, the batteries are for the program only, and do not control you're unit alone. So, if you hear someone tell you that some units run on batteries and some do not, that is false as it requires both a transformer and batteries on the programmable thermostat.Thank you and Sincerely,
Shastalaker7
PS Once in a while, you will find a programmable stat that has no batteries and will use the 24 volts from transformer only. These stats are normally used on 10 ton to 75 ton commercial units, and require no batteries. For example the Honeywell T7300 stat with a non switching QE-1003 Sub-base for commercial use.If you do have a programmable stat and you are having a problem with it going through batteries very fast, and you have an extra wire in the sheathed cable like a blue one and a C terminal not being used and the same at your furnace where the T-stat wires connect, a C terminal, take and wire that blue wire to both C terminals. This will take care of this problem.

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I have a true GDM46 and I cannot get the thermostat to adjust to a temperture of 36-40 degrees. What number should it be set at and why does it goes below or above the set you are trying to get. I put a new thermostat on and it does the same thing. Cannot adjust to refrigerate not freezing.


Did you fit a manufacturers original or an after market model?
When the thermostat was replaced was it fitted to exactly where the original thermostat was fitted?
These things are tempremental and must be fitted just so.

Mar 30, 2011 | True GDM-7 Beverage Cooler

1 Answer

I have a True GDM 26HL, The compressor and fan if plud in the wall works but plud in the unit it don't


Hi,
If the compressor and fan together come on when you bypass the internal plug then, no power is going to the plug. I cannot find a manual for this fridge, but I will tell you what to look for in order to repair it.
I believe that the thermostat which controls the internal temperature is not working. This part controls the operation of the compressor and fan. Check the following things. Some of this may seem silly, but if you had called me out on a service all, I would be checking these things.
I would get a multimeter from Radio Shack, or Wal-mart Usually less than $20.00. Harbor Freight has excellent units for less than $10.00.
Follow this procedure:
1 Check to see that the unit is turned on. (Normally the thermostat also has the "off" switch built in to it.)
2 Unplug the entire unit from the wall.
3 Locate the thermostat control. Turn the control on (DON'T PLUG THE FRIDGE IN). Open up the compartment that covers the thermostat's wiring.
4 The thermostat will have two prongs sticking out of it with two wires attached to it. Remove the wires.
5 Turn the multimeter to the setting of RX1 or 200 Ohms (a unit of electrical resistance). Connect the red test lead of the meter to "V" and "mA" and the black test lead to "COM" Then turn the meter on. Touch the two test leads together. The number displayed on the meter face should go very close to zero. Like 0.2 or something like that or all the way to zero.(0.0) That means the meter is ready to use for testing the power function inside the thermostat and the fridge.
6 Take the two test leads to the meter and touch the two prongs of the thermostat. If the display goes close to zero, the thermostat is good. If the meter does not display anything or signifies out of range. Then the thermostat must be replaced.
7 Call a Refrigeration supply house and locate a thermostat. In refrigerator terminology it is called a "Cold Control" If you ask for that, they will know exactly what you are talking about.
If it is not the thermostat, Reassemble the thermostat/cold control completely.
Check for a defrost timer. This is a device that would probably be on the back of the fridge(but could be next to the cold control inside, or in another spot) with a VERY small knob on it or a slot to insert a screwdriver into.
When you find it follow this procedure:
1 Plug the compressor/fan assembly into the dead outlet inside the fridge cabinet.
2 Turn the cold control to it's highest number (coldest) setting
3 Rotate the knob or screw slot of the defrost timer slowly. The fridge may come one.
If the compressor comes on, you need a new defrost timer.
I hope this helps you.
Best Regards,
Mark

Jan 16, 2011 | True GDM-26 Refrigerator

1 Answer

T49F true freezer thermostat does have a hot + ground or does it not make a dif. Likr other frezzers


as a general rule, in ALMOST every case, the thermostat just breaks one side of power. Usually one wire in and one out. I've not seen a double pole, single throw in a True, ever.

May 10, 2010 | True 52 cu. ft. / 1472 liter Commercial...

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