Whirlpool WDT750SAHZ0 Dishwasher Heater Problem

[CovenStine]

Need a new dishwasher and took a gamble on a used one that runs great but doesn't heat.
It seems to be a pretty solid unit, but I don't see an included tech sheet for me to use.

I got her home & tipped her over and tested 2 things:
Heater Element Resistance: fluctuates between 12 and 15 ohms- note that I'm using a Fluke gauge and cheap alligator clips, so I'm not sure if it's the clips or the element causing the variation, but it's not the meter's fault.
Thermostat behavior. It's normally closed, so I put it against a piece of sheetmetal, and heated- after it 'opened' I removed the sheet metal- Thermostat face temp was 71 degrees, and fell to 67 before closing again.

What would you suggest?

Thermostat?

Thanks!

[16345Ed]

You need to test for voltage coming out of board to heater while in heating cycle. 

Your element and TCO seem ok. 

You got a good deal because the board is probably fried. 

Edited February 7, 2019 by 16345Ed

[CovenStine]

Will do!

I never would've thought the thermostat would be set to 70 degrees F, but I'll set'r up and see what shakes out.

Thanks!

[darren412]

Like Ed mentioned check the heating system . Put it in self diagnostics and put your meter leads on pin 3and 4 of the P4 connector at the main control. You should be  reading 120 volts at the heating part of diagnostic testing.  Watch your meter !  If during diagnostics you don’t receive a 120 volt reading during the heating element test of the diagnostics, then as Ed mentioned you will have a fried relay or something on the main control.?  The heating element has a good reading of between 8-30 ohms  and the t-stat opens around just over 200 Fahrenheit. By pass it during the test if your not sure it is operating properly, but it sounds like it is ok. If it’s closing for you.   Make sure the wiring from the main control harness all through the heating element system is good before any testing also

[CovenStine]

So, I don't have the Tech Sheet that should've come with the appliance, so I can't really use it as a go-by to put it in Test Mode...

I tried a cycle, and hooked hooked up  insulation-piercing probes to both wires for the heating circuit that come through the hinge.
I read 0 volts and 13+/- ohms with the unit off, which tells me that the thermostat is closed and the heating element is connected, correctly.

Th;t being said, I never registered any voltage across that pair of wires, so for sure there isn't enough power getting through the hinge to power the heater.

If anybody has access to the manual for this (or can tell me what I ought to be doing, exactly  It would be very helpful!

Regarding the board & self-diagnostic mode, is that something easy to describe, I'd e very much obliged.

Looks like the inner piece of the door unscrews from the front, and I'm assuming the board is in there.

If the thermostat is supposed to kick off at 200 and it's kicking off at 73, isn't something not quite right there?

Thanks for your help!!

[darren412]

you need to call a qualified tech to look at your machine. your into an area that is not easily explained to a novice.   the process you are using to check the thermostat is not right.  Use a griddle that you can set the temperature reading on it. Then take your temperature readings with the meter leads attached to the thermostat at the same time.  You will not get the proper readings the way you are describing it.  Get yourself a membership here at Appliantoligy and you can have access to all that material you are looking for. If not, try googling your information  the explanation of what your thermostat temperatures are when opening and closing are a little confusing and not quite making sense.        If you run a cycle and then during the washing cycle(15 to 20 min) into the start of the cycle, if the water is not steaming out of the dishwasher when opened, then its possible your not getting heat out of the heating element.   OR   during the end of the cycle while its drying, the heating element should be hot under a heat selected drying cycle.        If none of this is happening then you either have a bad heating element, bad wires or a fried control board (most likely) as ED had mentioned.     Check the wires when they are disconnected like I mention to you  and if the wires have complete continuity through out the heating element system from the heating element terminal end to the thermostat and then to the control board like I mentioned then the wiring is fine.   From what you are saying about your ohm measurement readings on the heating element , it sounds like that is fine.   replace the thermostat if you can't check it properly.   if after that and you still are not getting heat from the dishwasher during a heated and drying wash cycle selection ,  then you will have a fried board (most likely)  as  Ed had mentioned.   If you can't do theses procedures with confidence and are not comfortable with working with electricity , then I highly suggest you get a qualified person who can do this who will have the proper technical information and hands on experience. Qualified techs are out there. you just need to know where to find them.  good luck  ok   

[CovenStine]

Thanks, Darren.
I am more than comfortable working with electricity, and usually have very little trouble diagnosing mechanical or electrical problems in a number of settings, but I probably shouldn't have even signed up at this forum based on the requirements for actual membership; so thanks for taking the time to spell all of that out, and for your suggestions.

Best,
C