I have no 220 coming out of the circuit board heat terminals when calling for heat. I jumped 220 to the heat wires and the element works. Will a broken thermistor keep the 220 from going to the heat terminals on the board?already switched boardout with a unit that was working. Same thing happens

Your heating coil is broken. IMHO. If it was working you would not get a voltage reading. Element is shorted to frame. Power flows through both wires the element is connected to. If the circuit is not interrupted their is no reading on a single line. You have an open heater element. Disconnect power from the machine. Remove the wires from the element and check continuity between the 2 terminals (no reading element no good). Check continuity between each terminal to chassis (should not get an ohms reading) If you get an ohms reading the element is shorted to the heater chamber. Sometimes an element will droop and touch when heated. You can sometimes free up the welded wire and reposition it. that is rare though.

If you need further help, reach me via phone at https://www.6ya.com/expert/dan_73bbd84fe1d95b61

Unplug hydro plug to fridge. Remove cover on circuit board. Follow wires from heating element, to terminals on circuit board. ( probably J7 and J8 ) . With an AC volt meter or multimeter set to AC voltage, turn fridge on hydro, and leave door open on fridge so that it calls for cooling. To be sure it's calling for cool, try gas first, when it's starts, you know it's calling for cool, then switch to AC operation. Now test for voltage at the 2 terminals that the heating element were/are attached to. If you get 100-120 VAC, then replace the heating element. If not get back to me and I'll walk you through a couple more tests.

To answer your question, "yes", replacing a heating element is a simple repair that you should be able to perform yourself. However, the problem may/may not be the heating element. There are several things that can cause a dryer no heat problem.

If the dryer runs, but does not heat, the first thing you need to check is the wall receptacle for the proper input voltage. A reading across the two hot leads (left and right slots) should read 220-240 VAC. If this reading is incorrect, check your breaker panel. Some homes have the dryer circuit on two breakers, vice one single 220 breaker. If the voltage at the receptacle is good, unplug the dryer and remove the cover on the terminal block in the back of the dryer. Plug the dryer back in and take the same voltage check at terminal block across the RED and BLACK wires. You should see 220-240 VAC if good. If the voltage is bad at the terminal block, but good at the wall receptacle, you have a bad power cord. If the voltage is good at the terminal block, then the problem is internal to the dryer.

NOTE: The reason a dryer will still run if the input voltage is incorrect is because the dryer drive motor only uses 110-120 VAC, while the heating circuits require the full 220 service. So, if you are missing a portion of your input voltage, the dryer may exhibit the symptoms you have.

If your problem is with the dryer heating circuits, the following link explains what to look for and how to troubleshoot:

http://www.fixya.com/support/r630242-dryer_runs_but_not_heat

Pay particular attention to the paragraph that discusses proper ventilation. The number one cause of dryer heat related problems are caused by poorly installed, kinked, or clogged dryer ventilation. Your heating circuits are located on the lower right side of the dryer cabinet under the drum. You will need to remove the lower kick panel under the door to access. The elment is inside the heater box while the Thermal Cut-Out (TCO) and Hi-Limit Thermstat is located on the outside of the heater box to the left of the element. The TCO is located in the rear, while the Hi-Limit Thermostat is located near the heating element terminals. NOTE: Make sure the dryer is unplugged while taking any resistance checks. Make sure you disconnect any terminal wires before measuring to ensure accurate readings. If you have any questions, please let me know. I hope you find this information helpful.

At most you may find a relay in a dryer. They're usually wired pretty simple. Keep in mind that 220 comes from both wires, and meets in the middle, the load. Be careful if you test live! A control may break just one wire. At a failed component, you'll have 220 on both legs, but no go. Jumping that component will make the unit run. Don't jump the elements!!! You can put a false load where the elements go, but it must be 220 volt, like two lite bulbs in series. I make my tester out of two lite bulb pigtail fixtures wired in series. At 110 they glow less bright then at 220.

Are you getting 120 vac or 220 vac at the unit? Check the voltage at the first terminals inside the unit as well as the breaker. You should have 220 vac at the elements and you are dropping a leg some where.

he prob. jumped the reversing valve wire (usualy marked "O" or "B" on the stat and terminal board
(defrost board)

Let's go over a few things: 

• Your unit uses 220 volts to provide heating.  Some elements are wired to one of the two 'legs' of the 220 giving you 'low'.  High uses 220

220 consists of three wires...two 'hot' (red and black) and a neutral which is white.  Neutral to hot will give you 110...hot to hot 220.  Measure accordingly and use care!  Neutral and the frame of the stove are effectively the same terminal...for safety.

• You say some of the wires are burnt or a fuse is blown.  They need to be replaced with proper wire...not just any kind.  There is high temp insulated wire available from many ACE and other home stores or parts shops.  It needs to be thick enough, too.  Make all connections carefully and fully onto clean terminals.  Tighten clockwise.
• Check the voltage coming to the element on various settings as above.  If you only get 110/120, you have an open supply issue which needs to be found.

Look for: loose wires, corrosion, burned insulation to ground.

Have you checked the voltage at the outlet? You're supposed to read 220-240 VAC at the heating element. Your dryer heating circuits require at least 220 VAC to work. The motor, however, only uses 120 VAC. That's why your dryer may be running, but the heating circuits aren't heating. I would go back and check your outlet. You may be missing one leg of the 220 service, or have a loose, burned, or broken wire in the plug or terminal block (on the back of the dryer). Let me know what you find. I hope this helps you.