View Full Version : True 2 door freezer warm case

09-15-2011, 08:11 PM
Hi folks,

After reading markettech's post "Help Us Help You", let's give it a shot!

I own a few coffee shops, and was a slot machine technician for 9 years prior. So I have electrical knowledge, and a small amount of knowledge on refrigerators that I've picked up over the last few years.

We're opening a new location, and all the equipment has sat idle for.... I'd say around 2 years prior to us coming in, and I'm told that the equipment worked under the previous owners.

I have a True, upright 2 door freezer which won't get cold. The compressor seems to run, but it would appear the defrost heater is running also at the same time. The evaporator fans do not run at all. The door switches are functioning correctly

My initial thought was to investigate the klixon. Switching doesn't seem to make any difference - it clicks, but the freezer just remains in the same state.

I am suspecting that the defrost termination switch is defective, as the resistance is reading low across all terminals.

Does this sound feasible? It sounds odd to me that the switch can be conducting both ways.

I did disconnect the purple wire from the Klixon, which goes to the defrost termination switch, to verify that the low resistance wasn't a short in the klixon. The klixon was switching fine.

Normally I'd take a chance and just order the switch, but for $65, I prefer the odds at Mohegan Sun rather than wait 4 days for it, find I'm wrong, then be back at square one when we're only 2 weeks away from opening day.

Thanks in advance!

09-15-2011, 08:56 PM
the compressor runs, but if the coil never gets cold enough to let the kilxon make the fans, it will never cool.. have you even checked to make sure its not a dead charge

09-15-2011, 09:00 PM
the evap fans aren't running because there is a coil temp. switch that wont run them until coil is cold enough. why not try kicking your defrost timer in to refig. manually and watching to see if the case comes down in temp. before you start worrying about a defrost termination switch

09-15-2011, 09:01 PM
You refer to a defrost termination klixon. Is this what the schematic calls it or you? In most self containers I work on, there is a klixon that shuts the fans off if the coil is above X degrees. Usually the eval fans will not turn on until the eval coil is around 10 degrees.
Have you looked at or cleaned the condenser? What temp is the box pulling down to? What refrigerant is in it? Can you take a suction line temp reading approx 6" from the compressor and a liquid line reading where it leaves the condenser?

09-16-2011, 07:29 AM
the compressor runs, but if the coil never gets cold enough to let the kilxon make the fans, it will never cool.. have you even checked to make sure its not a dead charge


I haven't checked whether or not it's a dead charge. That's something I don't have the knowledge/tools of. That certainly sounds like a possibility. I don't think the coils are even cooling but I will verify that when I'm down there today.

I did clean the evaporator coils... there was a lot of dust in there. As for the temperature of the case, the needle on the thermometer doesn't move at all. We're getting absolutely no cooling

redcell, sorry for any confusion... I'm suspecting the defrost termination switch attached to the evaporator, but have been doing testing at the timer box / klixon. I don't think it's a Klixon brand device.

I'll try some further investigation today, temps etc and see what I can find. Yesterday my investigation was impared because I was likely high on degreaser and paint fumes.

09-16-2011, 08:18 AM
Here's a pic of the wiring schematic for a 3-door GDM-72F glass door True freezer. It's not the same box as you have there, but I believe the defrost circuitry is the same:


The "Defrost Termination Switch", as they call it, is usually located on a mounting plate near the front side of the evaporator coil and it must reach about 20F to energize the fans.

If you suspect the switch is OK, I suggest inserting a temperature probe under the switch and watch the temperature after firing up the compressor. If it drops well below 20F and the fans don't come on, then just order a new one.

Some folks will "temporarily" bypass the control by connecting the fans directly to common and capping off the terminator, but you'll note in the picture, there's no heater limit thermostat on this particular freezer. (Some models do have limiters.)

If for whatever reason it gets stuck in defrost, the heaters will remain energized until the resulting fire terminates everything...including opening day. :eek:

09-26-2011, 07:44 PM
grab the discharge line on start up and see if it is moving any heat. If it isn't call a tech to find out where the leak is at.