The heater won't start.

It could be a fuse. They are small look kinda like a metal diode. Unplug heater, disconnect one side of power wire and do a continuity check on the heat strip circuit. You can also plug it in and do a voltage check on the two wires connected to the heat strip. Do this to see if you are getting voltage to the strips. Some heaters have safety switches that disconnect power when the heater falls over. It's a free swinging switch that might not have reset.

Your pressure switch may not be activating (ie closing and making contacts) This means you could have a blocked flue, clogged pressure switch tube or a bad pressure switch. The pressure switch is a safety feature to ensure your exhaust is not blocked and operating correctly. Find owners manual. Look at trouble shooting section. Open cabinet and look for error code light. If blinking 3 times, try "jumping" the pressure switch. To jump pressure switch you need to clear code be turning off power. When the unit/thermostat calls for heat the power vent fan starts first, this is when you need to jump the pressure switch. You need to do this in sequence. That is the unit first starts the power vent exhaust thus activating the pressure switch allowing the ignition cycle to the burners and heat. So the power vent fan needs to start first BEFORE you put the jumper on to bypass the pressure switch. Once the jumper is on it will call for ignition after approx 30 seconds. If ignites your problem is one of the 3 stated at the opening of this paragraph

If the switch is easy to access, you could simply replace it -- but finding the switch may be nearly impossible, because of the type of unit you are talking about. Also, some of these oil gel heaters have the electronics encased in a non-acessable area, meaning if one component goes bad, the unit is basically done. Your best bet to find the switch is to start with the manufactures website. if there are no diagrams or repair manuals, you should be able to find some contact information about repairs

see this causes and fix it. God bless you
User Control and Display Board If the washer won't start, the user control and display board may be defective. Check for power to the washer first.

Timer If the washer won't start the timer might be defective. This part is often misdiagnosed, check other components before replacing this timer.

Line Fuse If the washer won't start the line fuse might have blown.
Thermal Fuse If the washer won't start the thermal fuse may have blown. It can be tested for continuity. Watch our fuse testing video for more information.

Line Fuse and Holder If the washer won't start the line fuse might have blown, or the line fuse holder might be damaged and need to be replaced.

Main Control Board If the washer won't start the main control board might be defective. This is not common. Check other parts and causes first.

Door or Lid Latch Assembly If the washer won't start the lid switch assembly might be defective. This is a very common problem. The lid switch assembly can fail either mechanically or electrically. Test any electrical switches with an Ohm meter for continuity. The switches should have continuity according to their design.
Door Lock Motor and Switch Assembly If the washer won't start the door lock assembly should be checked. The door lock can fail either mechanically or electrically. Test any switches on the door lock with an Ohm meter. The switches should have continuity according to their design.

Incoming Power Problem If the washer won't start check to see if there is power at the electrical outlet which the washer is plugged into. Plug a lamp or radio into the outlet to check it. If the outlet is dead, check the circuit breakers or fuses for the home.

Power Cord If the washer won't start, check to be sure there is power to the electrical outlet for the home. If that is OK, the power cord itself might be defective. This is rare. You can check the power cord with an Ohm meter for continuity.

"LO" is simply informing you that the Heater is not sensing proper water flow through it! A Flow Problem.
A special sensor, called a pressure switch is this source. But... That does not mean it is bad - No, it is in most cases just doing its job!
Most common reason - Dirty Filter.
A good cleaning of the cartridges, or maybe a breakdown and recharge of a DE Filter, or a good cleansing backwash of your sand filter, will remedy this situation.
Or... Check for any OTHER reason or situations water flow may be reduced through the heater:

• enough water in pool or spa?
• If you have a weir gate in skimmer, is it stuck in the UP position?
• Are any valves closed?
• Do you have a bypass valve at the heater?
  • If open, this will reduce the amount of water going thru heater, close it to the point, LO goes away.
• Could be debris in front of Pressure Switch, in the copper tubing
  • Unscrew and remove pressure switch, turn pump on. But first, align end of tube so that when water squirts out it will shoot out from heater and not onto electronic heater components!
• If all above is good, you may have failed pressure switch?
• Etc

Good Luck - hope this helped.

do the following steps: God bless you
To start test program, press and hold both POWER SCRUB PLUS and RINSE & HOLD program buttons, then turn unit on by pressing ON/OFF button. When program buttons are released, lights above them will flash. To end test program, press ON/OFF button.To check program indicator lights (POWER SCRUB PLUS, REGULAR WASH and RINSE & HOLD), press and hold each program button. When REGULAR WASH program button is pressed, CLEAN light also comes on.
To start testing, press both POWER SCRUB PLUS and RINSE & HOLD buttons a second time. When testing has ended and a fault was detected, the following indicator lights will be lit:
POWER SCRUB PLUS = Heater fault
REGULAR WASH = Water filling fault (over or under filling)
RINSE & HOLD = NTC (temperature sensor) fault ? note circulation motor stops shortly after it started during an NTC fault
To check for heater, high limit or flow switch problems, start testing until heating starts. Using a meter with a current coil, measure current going into dishwasher. If current is ~ 11 A, then heater, high limit and flow switch are OK. If current stays at ~ 1.5-2 A, then heater, high limit or flow switch are faulty.
If water level switch (f1) has failed (opened), REGULAR WASH light will come on and unit will continually fill and drain where testing won't be completed. If flow switch (e5) has failed (opened), water won't heat (to 150?F) and water won?t stop circulating. If NTC probe (f2/f4) has failed (opened), RINSE & HOLD light will come on immediately and testing will end shortly after water has started circulating.
If more than one fault occurs, more than one light will be lit.

you might check your switch sounds like to me that your two lower speed sides of the switch maybe burnwed out.