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When I check any wiring, I always check the wires against themselves for a short and short to earth, also the resistance of the wires. All of the wires I’m question have 0.01 ohms. That is what I mean by checking the cables.
What else is in the circuit that controls heating. Flow through heater + thermostat, temperature/ turbity sensor, circulation motor + tacho sensor and wiring. The only thing I was unaware of is how the tacho sensor may have been an issue due to Dave informing me of it.
What can I say I enjoy a challenge in finding out how things work.
from what I can see you have covered all the bases and am now at a loss as to what to suggest
to be able to heat the machine has to determine sufficient water flow before it turns on the heater
that’s the basics anyway
Dave
Flow sensors normally work on 5v DC & would have 3 connections, usually the outer 2 connections are the 5v supply and the middle connection is a Square wave output back to the control pcb. The DC supply is easy enough for you to check with your meter, but to check the output you need a good analogue multimeter or preferably an oscilloscope. You would really need to check that at the control end for the Square wave and the sensor for the 5v. For reliable sensing the output needs to be at a stable 5v.
Forgot to ask earlier: Have you checked that You’ve got good water flow into the machine and through the inlet valve ?. Without good input then you won’t get a good signal from the flow sensor.
So the other day I put the dishwasher back together, powered up and entered diagnostic mode, cleared the faults and ran a cycle in diagnostic mode. The cycle lasted around 20- 25 minutes (not sure if this is normal for diagnostic mode) and I had a thermometer probe in dishwasher. Temperature got to 38 degrees Celsius (again not sure if this is normal for diagnostic cycle). When finished, I came out of diagnostic mode and loaded dishwasher up with a normal dirty load. Set it to “wash tablet” and set to “auto”. When I set it the dishwasher off normally, it takes a few minutes before starting, and when started I usually hear the drain pump first. This runs for around a minute, then stops for a few seconds then starts again just for a few seconds and then the fill starts. What actually happened when I started the dishwasher off this time, was that this cycle started and it started filling whilst the drain pump was still running. This cycle kept repeating and I left it running like this for around 10 minutes. Eventually I opened the door, no water inside, and closed it again. This time it ran the drain cycle as usual, and then filling started (with the drain pump this time not running whilst filling) and started to run as it should. The only thing was the temperature only got up to 29 degrees Celsius (manual says 40 – 75 degrees Celsius for an “auto” program”) part way through it drained all the water and refilled, temperature only 21 degrees Celsius.
Specialist01269 I did read something about the flow sensor being an issue if you have your machine draining and filling at the same time, but why would this stop the heating?
Very odd this is.
I’ll check the inlet pipe next then
If there isn’t enough water flowing through the heater when energised, then it will quickly overheat. The processor measures the flow of water by counting the square wave pulses from the flow sensor and comparing them to an internal map, if the pulses don’t match the map then the heater won’t get power. It protects the heater and machine.
Could be something as simple as low incoming water pressure, has the water been off for any reason ?. Is the water tap feeding the machine fully open ?, Is the filter on the inlet valve Dirty / Blocked ? etc.
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