Is there a defrost switch or something in small Welbilt refrigerators?

SOURCE: Maytag MSD2356 Freezer frosts up quickly, fridge warm

If you jumped the defrost board and it went into defrost then that board is bad. I assume by "freezes up" you are talking about the evaporator is frosting up? That defrost board puts it into defrost automatically. If you have to jump it to get it go into defrost then the board is not doing its job.

SOURCE: Refrigerator Defrost Troubleshooting

you cannot do this
just check the defrost heater and the bi metal, if they check good then the adaptive defrost control is bad

SOURCE: Problem auto defrost refrigerator

i have a refr. G.e TFG27PF Profile and have some bad smell like a wire short. i looke all ever and it looks ok and the refri. is working ok. today sudenlly the DF light started to blink what is the problem/ thank you for a fast answer.

SOURCE: My freezer is running fine

HI. There are two causes here, in this situation. The most common will be a faulty defrost timer, or adaptive defrost control board. The defrost mechanism will vary form unit to unit. Most newer units will be equipped with an defrost control board. This will be located in the control housing, just above the heat shield, in the upper right had side. Older models will have a standard defrost timer mechanism. If this device fails, the evaporator heater Assembly will not receive the command to defrost the coil, on time. The easiest way to isolate the cause, will be to test the heater element. If the element is functional, the defrost timer/board, will be the culprit.

Defrost heater assembly test procedure:

The defrost heater is usually located at the back of a side by side freezer or under the floor of a top freezer. It will be necessary to remove obstructions such as the contents of the freezer, freezer shelves, ice-maker and the inside rear or bottom panel of the freezer, to access.

The panel may be held in place by retainer clips or screws. Remove the screws or depress the retainer clips with a small screwdriver. On some older top freezers it is necessary to remove the plastic molding to access the freezer floor. Removal of that molding can be tricky, so try not to force it, if possible. If you decide to remove it, you do so at your own risk. it will break, if forced. Warm it first with a warm towel, or hair dryer, set to low heat.

There are three primary types of defrost heater elements; exposed metal rod, metal rod covered with aluminum tape or a wire coil inside a glass tube. All three elements are tested in the same way.

The heater is connected by two wires. The wires are connected with slip on connectors. Firmly pull the connectors off of the terminals (do not pull on the wire). You may need to use a pair of needle-nose pliers to remove the connectors. Inspect the connectors and the terminals for corrosion. If the connectors are corroded they should be replaced.

Test the heating element for continuity using a multimeter. Set the multimeter to the ohms setting X1. Place a probe on each terminal. The multimeter should display a reading somewhere between zero and infinity. Because of the number of different elements we cannot tell what your reading should be, but we can be certain of what it shouldn't be. If the reading is zero or infinity the heating element is definitely faulty, and should be replaced.

SOURCE: Amana refrigerator with freezer on bottom frosts

NOTE: This
is a multi-solution answer since I don't have all the tech from your question to pinpoint your problem
But the solution is in here generically, if you read and study the solutions very,very carefully.
First I would check cold control. Thats where you turn it off, if your temp is not warm. it can
be defective and not shutting off. If your temp is warm proceed with the following.
I would check the fan in the freezer. Listen to see if it is running
It moves air to the ref from the freezer
Then check to see if FREEZER CONTROL is turned WARMER WHICH MAKES THE REF COLDER AND VICE-VERSA. SEE?
The ref. temp should be about 33-35
The Freezer temp should be 0 to 10 Any thing below these temps is overkill and a waste of elect
The higher the number you turn it up to is the coldest
But is probably a common defrost problem The ice build up
is not being melted by the defrost system.The fan can't blow through the coils into the fridge.
Take out back panel of freezer to check for ice buildup. The coils should be clean.
There are three components to a defrost system- a heater,heater thermostat, and a timer unless you have a defrost electronic card.
Its best handled by a Technician but you could possibly do it by taking your model number to the nearest appliance parts store and asking for the parts. They are mostly located in freezer ,behind back panel on freezer coils.except the card which is usually located in ref The parts store will have info
Also check fan undernearh Ref in the rear
Clean condenser coils underneath
Make sure back cover is on the fridge. Some take them off and throw them away.
make one out of cardboard if its gone, using the holes of the old one.
.I'm including my article on Refrigerator Repair for your help and convenience.;
Please click or copy and paste into browser for Article

http://www.fixya.com/support/r5816737-fix_refrigerator_psychologically

If you need more help go here:

http://www.applianceaid.com/procedures.html

MORE TIPS AND TRICKS:
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STOP PAYING FOR EXPENSIVE WATER FILTERS FOR YOUR REF. DO THIS====
http://www.fixya.com/support/r9962087-stop_paying_high_price_refrigerator
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WATER SPLASHING IN FREEZER AT ICEMAKER
THE FILL TUBE IN BACK OF REFRIGERATOR CAN SLIP
AGAINST THE FILL RESERVOIR CAUSING A PARTIAL BLOCKAGE
OR BECOME CLOGGED WITH ICE.
REMOVE THE ICEMAKER AND INSPECT THE FILL TUBE.
RUN WATER IN TUBE TO ELININATE BLOCKAGE AND CHECK
TEMP IN FREEZER. IF TEMP IS BELOW 0 DEGREES, THATS
OVERKILL AND USUALLY A WASTE OF ELECTRICITY TO KEEP IT THAT COLD, NOT TO MENTION THE FILL TUBE FREEZING UP
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Leo Ponder
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