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FIXED GDM 35 True Fridge won't cycle off

mendozer

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May 6, 2015
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35
Location
Seattle
Model Number
GDM 35
Age
6-10 years
I have a True fridge that just today won't seem to turn off. I have it plugged into a digital controller (Inkbird). It came that way to me as the previous owner removed the knob thermostat and used this. It's set to 34 and has a limit of 38. It normally kicks on and cools down in under two minutes. Today the alarm was triggered at 45 degrees and it's staying there. This is despite my internal thermometers showing 38 (metal fridge one you put on the shelf). I didn't change anything about the thermo controller. I was reading about low refrigerant, bad relays, etc. I've done the basics: coils are clean and dust free, all fans are working, no obviously failed or fried relay plugs. It's been on for several hours now. Part of me wants to try plugging it in directly to the wall, but there's no internal thermostat so I don't know what would happen. Other part of me wants to wait and see a day. thoughts? I know it's a true and not a consumer brand, but same principles apply. It's a full fridge, no freezer so it's just a condenser, fan assembly, and evaporator with another internal fan blowing from the top.

GDM 35 if that matters
 

Dan O.

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Is your complaint that it is running (compressor and fans) but not cooling properly?


Dan O.
 

mendozer

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Location
Seattle
well both. It runs and runs but barely chills and when it finally does, it turns off (so im thinking relay is fine). I even had to adjust the digital controller to artificially set the temp lower and it thinks it's 37 so itll shut off when really it's like 42 in there.
 

mendozer

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I also just learned yesterday while out renting a vacuum pump and AC manifold set (thinking i was going to recharge it) that Washington banned sales of 134a in january this year. Damn state gets more restrictive. So i can't even find 134a if i wanted to, unless i pay a commercial person to come out and do it = $$$. Is there a compatible substitute?
 

Dan O.

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If the refrigerator is running but not cooling sufficiently, the next step is usually to examine the frost pattern on the evaporator coil.

mendozer said:
I even had to adjust the digital controller to artificially set the temp lower and it thinks it's 37

If whatever controller you're using is not reading the correct temperature, I would say it is likely defective.

mendozer said:
Is there a compatible substitute?

I do not know that and I can't assist you with refrigeration system work. If you're not certain what you're doing, I'd suggest you not tamper with it.

JMO


Dan O.
 

mendozer

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Location
Seattle
when i mentioned the controller it is accurate to temp. I have a manual one in there as well. But it would not cool to my setting of 35 so I had to "calibrate" the controller lower so it thinks it's 35 when really it's barely getting to 40. What would I look at on the evap coil? I have the True service manual but it's not very specific. "inspect item and if defective replace" lol
 

mendozer

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did a little DIY and the evap coil was completely iced over! I'm trying to defrost it rapidly now
 

Dan O.

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mendozer said:
What would I look at on the evap coil?

The frost pattern. If you posted a photo we might be able to suggest professional opinions.

Evaporator frost pattern and their likely causes.
Frost Patterns.jpg

it would not cool to my setting of 35 so I had to "calibrate" the controller lower so it thinks it's 35 when really it's barely getting to 40.

I'm sorry but I still don't understand. What happened when you set it to 35 before "recalibrating"??

Dan O.
 

mendozer

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Pictures. I couldn't upload it earlier
 

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Dan O.

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If that is a picture of the evaporator coil totally solid with frost, that will be why it isn't cooking. Thoughtfully defrost it and let it run for 6-12 hours then take a photo of the evaporator again.

Do NOT attempt any tapering of the refrigeration system. It is NOT your problem.


Dan O.
 

mendozer

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I melted it all down and cycled it back on how the heck did it even get that cold. I've only had it for four weeks.
Also when I said calibrating the thermostat before I'm using an inkbird thermostat. It has a set temperature and display. When it wasn't cooling I had to artificially "lower" the temperature basically skewing the set temp so it would cycle off when it hit temps which is wasn't technically doing. I'm resetting it back to normal settings as we speak
 

mendozer

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seems like my next step is figuring out why the defrost timer isn't working. Reading through the manual i looked at the testing methods and looked under the front grille...no timer in sight. So that's odd
 

Dan O.

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I guess it's a good thing you didn't go mucking about with the refrigeration system.

There are other components in the defrost system besides just the timer. I do not know how that specific model was designed though so which exact components it uses in unknown to me.

How does a frost free refrigerator's defrost system work?


Dan O.
 

mendozer

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it's now 2.5 weeks later after manually defrosting it. I had it set to 34 originally. Maybe that was too cold causing it to ice over. So i set it to 36. today this was noticed as it wasn't turning off. so something's definitely wrong with the defrost setting. The evap coil tray (where things are supposed to melt into) is bone dry
 

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Dan O.

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You are operating it with a cover in place over that evaporator coil right?


Dan O.
 

Dan O.

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It's definitely not defrosting. I'm afraid I have no idea how that is accomplished on that model. I do not know what else to suggest, sorry.


Dan O.
 

Dan O.

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I did see this in one sales brochure for True refrigerators.

True brochure said:
There is not a defrost timer as the temperature control will initiate the off-cycle defrost during each refrigeration cycle.

a. At this time, the compressor will and the evaporator fan(s) may turn off. Defrost heaters are not installed on refrigerators and therefore will not be energized.

b. After the evaporator coil temperature has been reached, as determined by the temperature control, the compressor will restart.


I do not know if it pertains to your particular model however if it does, it may not function correctly with an external thermostat control system. The above describes the functioning of a 'cycle defrost' refrigeration system.

JMO

Dan O.
 

mendozer

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Location
Seattle
interesting. The previous owner swapped the original control for an inkbird stating it worked better. maybe he didn't know what he was doing
 

Dan O.

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maybe he didn't know what he was doing

Once you get a tech that is familiar with the system maybe you'll find out.

'Digital' is not always better and I myself try to avoid electronics whenever possible.

JMO

Dan O.
 
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