Micro Matic MDD-23 kegerator - compressor constantly cycles on & off.

[Smksignals]

Hello everyone,

I purchased a used Micro Matic MDD-23 kegerator and have a question. The compressor constantly cycles on and off, roughly every 2.30 minutes. 2.30 minutes on, 2.30 minutes off (give or take 5-10 seconds). Almost like it runs on a timer. I wonder if this is normal? I have some details below to help trouble shoot if not normal.

Unit is 12 years old
75 degree exterior room temp
T-stat set at 3 (where the yellow triangle is)
Interior fan/tower fan runs continuously
Single 1/6 keg in the kegerator (1/2 full)
Inkbird temp data logger shows a constant 39-40 degree temp inside
Put bright light in unit, closed door, turned off lights in room, no light seeping through the door seal.
Used a dollar bill in between the body and door. Slight resistance pulling the bill against the door seal.
Checked condenser coil, looks very clean. Hit it with some canned compressed air to blow of any residual dust.

FWIW the beer comes out great. I balanced the line and little to no foam comes out of the tap. It seems like the compressor is excessively running to me, but I don’t know if this is normal. Any help is appreciated.
Thanks.

 

[Smksignals]

Hi again. It's been a couple of weeks with no reply. Maybe my post being model specific is making it difficult to answer? I believe the BeverageAir BM-23 is the same model. I also found out both of these models are manufactured by Nordon Inc.

One more side note, I added 3 Corney kegs filled with water to fill up the void inside and add more mass. The compressor now runs 3:30-3:45 minutes, and remains not running 3:30-3:45 minutes. Darn near like it is on a timer. Inkbird temp logger still shows 1 degree fluctuation, between 39-40 degree's. I sent a note to Micro Matic with no response. Not surprising being the unit is 12 years old.

Any concensus on what normal cycle times are on a 1/2 barrel kegerator with a compressor? I did search compressor cycling here and couldn't find any posts on times cycling so quickly. Mostly of the posts are on long running times.


Thanks again, Kurt.

 

[NTexBrewer]

I’m not familiar with your kegerator but wonder if you can just use an Inkbird temp controller. Set the kegerator to the coldest setting and let the inkbird do the cycling for you.

 

[day_trippr]

The cycling does seem excessive - even nearly empty the period is so short it may actually be stressing the compressor. Makes me wonder if the seller knew something wasn't right and unloaded it.

I would contact Micromatic directly and see if they'll point to a resource that could help figure out what might be happening...

 

[Dr_Jeff]

It is the thermostat that controls the compressor turning on & off. The inside fan should stay running all the time.
You said that it gets cold and will maintain the temperature, so we know that the compressor and associated things are good.
It sounds to me like someone might have replaced the thermostat with one that is too sensitive or the one in there is starting to have issues. You can find them on Amazon for ~$20 and under. They are easy to replace, there are two thumb screws on either side of the evaporator tray and it comes right out, the fan is attached to the tray. Be careful with the capillary tube, it is usually routed into the coil via a tube specifically for it with it going in from the left. The thermostat is held in with two screws and has two wires going to it, usually slide on spade type connectors, occasionally they will be attached with screws. It's a simple 10 minute job.

My best guess.

I've bought and sold several BM-23 units and have two now.

 

[bkboiler]

Hmm...12 years is getting on in age...
I was looking into this recently and you can pickup a recharge kit for $30 for all the tools and gauge and $30 for a few cans of R-134...not too bad $60 for a DIY repair...
although chest freezers are on sale right now...

 

[day_trippr]

I don't think the symptoms point to any weakness in the compressor, evap or condenser, simply because it doesn't linger in the cold portion of this extraordinarily short cycling. On vs off seems to be pretty close to 50% wrt time, while the more classic end-of-life failure symptoms have the on period dwarfing the off period.

I think it's most likely the thermostat has gone hinky...

Cheers!

 

[bkboiler]

I don't think the symptoms point to any weakness in the compressor, evap or condenser, simply because it doesn't linger in the cold portion of this extraordinarily short cycling. On vs off seems to be pretty close to 50% wrt time, while the more classic end-of-life failure symptoms have the on period dwarfing the off period.

I think it's most likely the thermostat has gone hinky...

Cheers!

Ahhh...I think this spells end of life for my vertical side by side then...
Been running pretty much all day; thinking I may go get a 7.0 cf chest freezer tomorrow.

 

[sibelman]

The controller in my commercial Kegco kegerator allows config of the temp spread, 7 degrees by default to minimize the compressor stress @day_trippr mentioned. Dunno if the MDD-23 can be tweaked, though the previous owner may have wanted to minimize temp swings at some cost to compressor life span.

 

[Smksignals]

Thank you everyone for the posts so far...

I agree, I am leaning towards the t-stat. I am going to dig into that further. I also have an Inkbird connected to my ferm-chamber. I might hook that up to the kegerator and play around a bit.

I'll make sure to keep this thread updated with any changes.

 

[Gdubss31]

did you ever figure out the issue? I had a similar issue with a True TDB-24-48-1-G-1LD. I ended up replacing the thermostat, Capillary tube, even got a new compressor. It ended up running 2-3 minutes on and off. It took about 1 full week to get it to temperature and recently stopped cooling. My HVAC guy did the work and can't seem to find the issue, he wants to install a TXV valve to see if this helps.

 

[Smksignals]

I did not. Ended up selling it on the cheap and went the keezer route.

 

[Gdubss31]

I might have to do the same.

thanks