Hill Phoenix Wallmart Freezer blowing fuse in MR4 Temp Controller

[ronaldmaustin]

I have a Hill Phoenix Walmart commercial freezer. The Johnson Controls MR4 Temperature/Defrost Controller stopped lighting up so I replaced the unit with a direct replacement unit of the same make and model. The wiring was simple and done correctly. Upon plugging the $250 MR4 in, the temp indicator lit up and everything seemed to work. Then in about one minute of operation, I heard a pop, the MR4 unit was no longer lit, and I even smelled an odor as if some electrical part had burned up.

So that is two burned up MR4 control units. I cannot find where there is any fuse in the MR4 control unit, so maybe one of the relays burned up. In any event, does anyone have any idea of what the problem may be?

[al]

Check the voltage feeding the controller, check the fans, solenoid etc for shorts/burnouts. Is there a transformer feeding the controller?

al

[Grizzly]

Hi Ronald.
Just as soon as my Internet connection to mediafire stops playing up.
I will upload the 4 page pdf for the MR4 Controller.
Page 1 shows the input voltage as 24v AC.
So I would be checking your transformer voltages. Also your defrost switch rating is 8A as is all the others.

There is also a test function prior to connection to any sensors or other outputs.

At this stage I would assume the unit has fried, sorry!

You do need to verify your incoming voltages then prove any of the switched output functions.


Basically just as al has suggested.
Grizzly

[monkey spanners]

One of the questions to ask yourself when changing a faulty part is 'why did the part fail?'

[Grizzly]

One of the questions to ask yourself when changing a faulty part is 'why did the part fail?'

Wise words Monkey, sadly not asked often enough!
Grizzly