Hotpoint WD640 errors F-07 and F-08

[937carrera]

Bit of a long story.

My WD640 had an F-08 error, after reading around I checked the heaters, thermistors and all seemed to be OK on a resistance test, about 30ohm on the heaters, 25Kohm on the thermistors. Everything was pointing to the PCB.

I removed the PCB and inspected it, hoping to find a dry joint. Nothing was showing up so next was to identify the relay connections and check continuity on the board. Again all OK, so next was to check operation of the relay by using a 12v source. That was a mistake, there was some sort of feedback in the circuit and a small component failed. I have not been able to identify what, but the board is back in the machine it powers up and after a short time cycles on and off. So, I destroyed the board, not sure why unless the connections to the relay were polarity reversed to what was expected.

So, next I got a replacement board. I thought it was the same, but some of the connectors were different. I traced the circuits on the board and found the corresponding positions and made up a suitable edge connector block. Connected it all back up and still had F-08. Shame but it seems that a WD640G and WD640P are electrically the same

I then spotted that the water fill valve was permanently running as was the discharge pump. Was this a clue. I removed the water heater element for inspection and then the outlet from the drum. That was when I found the original problem. Coins & stuff in what I suppose is called a filter, with something stopping the plastic ball from dropping down.

Cleaned, reassembled put the machine into discharge mode and it completed the 2 minute cycle to the end without error. Great

Final check was to put a load through the washer. The cycle starts but after about one minute I now get an error F-07. As I understand it this also points to the water heater relay. Having checked for resistance I  then decided to do a live test. There was only 140v AC across the water heater element. 237V across the dryer element when it's in dry mode.

My conclusions are that:

F-08 can also be linked to a blocked drain valve filter - wish I had known that before, making this post partly so it might come up on a search

F-07 is an error for low voltage at the water heater element.

So. what to do next. I suspect the replacement board has a fault on it.

a, get another board, will that be OK ?
b, remove relay K2 and replace it. I did read somewhere that someone removed the top off the relay and cleaned the contacts, but that doesn't seem to be possible without destroying the casing
c, something else

Suggestions welcomed, everything else on the washer seems in great condition.

Thanks in advance for any help

 

 

 

 

 

 

 

 

 

[Whitegoodshelp (Andy)]

You could try sending your board to be checked, repaired, or replaced by a reconditioned one to QER repairs who specialise in washing machine PCBs

[937carrera]

Thanks for the reply Andy, sorry I didn't see it before so have now changed my settings so I see replies immediately.

I managed to get another board this week and fitted it this morning. This second board is behaving exactly the same. pump out fine, drying fine, put it on a wash cycle and after a minute error F-07 pops up and the dryer fan comes on. Only thing to do is switch off at the mains.

As before only 140v at the water heater.

So, either both replacement boards have the same problem, or something else is at fault. Hmm

I decided to retest the water heater element again as I had read one situation where there was in internal short to earth. Zero continuity between live to earth and neutral to earth.

Next I double checked the resistance on the heater element. Looks like it's gone open circuit now. Could I have damaged it when I removed / replaced to inspect it ?

Could that throw the F-07 error code

[Whitegoodshelp (Andy)]

An open circuit heater will definitely cause major issues. On some machines it can cause the entire washing machine to stop working. You can’t cause one to be open circuit unless maybe it was dropped from a great height.

[937carrera]

If the machine wasn't so heavy perhaps it would already have been dropped from a great height

I'll get a new one from you & see how that goes.

[937carrera]

A further update: She's alive

The water heating element arrived yesterday (good service from you & DPD as I only ordered Saturday PM) and was fitted this morning.

I put the meter on and the heater was showing 31 ohms, thermistor around 22k ohms. I did notice the element was 1700W rather than 1800W on the original, so the water heating will be a little slower. The thermistor was also on the other side of the earth, but no problem as the connecting wire is long enough.

Tried a pump out- all OK

Tried a quick wash program as a test. Got three minutes in without an error F-07 throwing, tested the voltage and was seeing a full 230 VAC

The machine has now completed two complete wash cycles and the backlog mountain of washing is coming down

It's really quite strange that the original F-08 was solved, but an F-07 remained. The original heater element was definitely showing around 30 ohms, and metered out OK so I am glad I rechecked my work and found the open circuit. I spent hours tracing and rechecking the circuit boards to adapt the edge connectors to a different configuration.

It appears that F-07 may not always refer to a failure of the heater relays, perhaps the output is limited by the board in some way to 140 VAC when the current flow is not what is expected, I'm not sure how clever the electronics on the board is ?

Posting for posterity to hopefully help others, but also in case there's further insight.

Curious how what seemed to be a blockage on the float was fixed and a second problem presented itself. Maybe the heater element was the issue all along, even though it checked out with a meter OK originally.

I think I now have a spare control board as the first replacement I bought showed the same F-07 error. I hope I never need it.