Weird heating issues w/WDF520PADM7 and FH error MFW9700SQ1

[ameritech]

Hey there,

1st unit is a Whirlpool dishwasher WDF520PADM7 "no heat poor wash" and found the relay closing and an open element, so ordered, returned, installed, and everything was fine for a week. Then customer says same thing. Was out yesterday and element was heating in test but had same 7-1 error. Besides the obvious causes, this error says in tech sheet that control is programmed to "disable" heating circuit if it "detects a problem". 

Just to make things complicated, I also got a new error for the wash motor (4-3). motor seems fine and water flow strong however. There was a bit of trash on the spray arms although I had cleaned out a good but the 1st visit. I went ahead and reseated the motor harness as I know some whirlpool motors had issues with the harness connection. Any thoughts?

At this point I'm leaning towards control. Could the relay be geting stuck causing the control to disable the circuit? What both these errors have in common is the control. Kinda grasping at straws here...

2nd problem:

Maytag frontloader MFW9700SQ1 FH error. First time out found reversed water lines. pressure switch and hose tested good via inspection and "blow test". Water pressure was good and strong. Checked "air pocket" press. hose @ tub is connected to. Drain pump was excellent. Only time it threw error was when I disconnected the flow meter harness. Besides that filled tumbled several times fine. 

Second time i came out I installed a flow meter customer had ordered off ebay. Only time saw  error was when I added detergent to a load of clothes. Now... he is using 10x concentrated and I told him this was a no go. I saw something about bad pressure switch causing this due to excess/non HE deterg. Do you think thats the case even though the error is so intermittent?

Many thanks,

Jared

[CrazyCarl]

Check your NTC thermistor. And look at the notes section for the service cycle. The control will check the thermistor at certain points and you can compare that with your manual check of the thermistor. These dishwashers are notorious for bad wash motors after just a few years also. I see a lot of pumps go bad and you’ll get the 7-1 along with 4-3. If the thermistor checks out and the board checks out and the issue persists, there’s a good chance the washpump is not running continuously during the cycle 

Bit of a long shot here, but next time on the front loader, fill it with water start the drain and then unplug the unit. If the water drains itself out at that point your drain hose is too far down the standpipe and the washer is siphoning the water out

 

 

[Vance R]

For dishwasher 

+1 for wash motor and thermistor. Clear the error codes and indicated in tech sheet. Run the diag cycle to force a sensor calibration for the next load.

For washer

If the customer has been using too mush detergent the pressure switch hose may need to be flushed to clear deterg residue. Recommend only using 2 table spoon of HE detergent max per load.

[ameritech]

Thanks guys. The NTC would be located on the board right? I'm just checking for decreased resistance as the wash motor circulates correct? I asked the customer if she ever noticed the dishwasher stop running during a cycle but she wasnt sure.

On 2/12/2021 at 9:04 PM, CrazyCarl said:

And look at the notes section for the service cycle. The control will check the thermistor at certain points and you can compare that with your manual check of the thermistor

 Carl...  when you say service cycle, is that the same as the 1-2-3 key dance? How do you see the thermistor checks made by control? (model has no display). I hope I'm following you...

Vance: what is your method to flush hose? I blew thru it and didnt seem like there was much of a clog. I also examined every inch of it for holes/wear.

Thanks!

 

[Vance R]

21 minutes ago, ameritech said:

The NTC would be located on the board right?

The NTC is in the OWI. spec from page 5 of tech sheet . 46k to 52k at 77deg f, 11k to 13k at 140 drg f.

26 minutes ago, ameritech said:

what is your method to flush hose?

Old zoom spout oil bottle or a ice surrender kit syringe. Flush from the pressure sensor end with water.

 

30 minutes ago, ameritech said:

when you say service cycle, is that the same as the 1-2-3 key dance? How do you see the thermistor checks made by control? (model has no display).

I'll try answering for @CrazyCarl Yes.   Watch the leds that are light up to determine which step your in of the daig cycle. Very hard to follow BTW. Clear the error codes in step 19 by pushing select button. At the end the board will report new error codes if any.

[ameritech]

Ok... So yesterday I applied all the good info from both you guys and dug in with some troubleshooting. So the NTC was at spec at 34 K ohm after running a few cycles. Both the NTC and the OWI passed with flying colors per the notes on the service cycle. I even removed the OWI harness @ board to see if control would catch it--it did.

 But here's something that was weird... the first interval on service cycle that the heater is supposed to be on (9 to be exact) wasn't activating it, the last interval however at the end the heater was piping hot. Not sure what to make of that,  but the heater obviously CAN function, and there were also no service errors at the end of the test. 

So, all that to say... we're most likely looking at a bad wash motor. Any additional thoughts?

 

[Vance R]

24 minutes ago, ameritech said:

Any additional thoughts?

Very possible to be a intermittent wash pump. Seems like alot of those get replaced.

[ameritech]

As an update, it has been over a month and the last I heard form the customer it was running fine. I forgot to mention that the notes said that after running the service cycle the next *normal cycle would be a calibration cycle. So maybe this whole time they just needed the heater but I also needed to calibrate it via tech sheet?? We may never know, but at least the is case is closed.

Jared

 

[philcheck]

NEW STUFF is too dam complicated