Fisher Paykel DD603 Heater Thermal Fuse Question

[deepsquatter804]

Hello, I have a DD603 that developed a huge leak in the top drawer. The heater plate melted the tub and the seal failed. Luckily the flood sensor worked and it shut off. I've had this thing for 15+ ears and have had a number of service calls so I'm used to the F1. I pulled the top drawer out and cleaned up/dried all the water. I then pulled the bottom drawer out and dried up/cleaned up the water. I've dealt with this probably 20 times over the  years. Split hose, failed top seal, crust build up on seal and so on.

This time however things went in a direction I wasn't used to. As I said, the tub melted as did the locking ring. The thermal fuse on the heater plate did not blow. I replaced the melted tub and locking plate. At the same time I replaced the pump/motor as well as the rotor. The rotor was chewed up and the pump had gotten noisy over time.

Anyway, I started the unit and it ran quietly for about 1/2 a cycle. Then it went dead. No power. No LCD. Nothing.
I had a spare controller so I plugged it in just to make sure. No change.

I took it apart and the thermal fuse on the heater plate was blown. I installed the original plate to confirm. Again it started right up and ran for a partial cycle and died again. No power. No LCD. I haven't taken it apart again but I'm sure the fuse one the plate has blown again.

What could cause the machine to blow the thermal fuse on two plates?

By the way, the bottom drawer has worked fine through all of this.

I read (on a q&a board - not here) that the main chassis circuit board could be the problem but that doesn't make sense to me. If that was the cause, it seems that the bottom drawer would be affected as well.

So, what could cause the top drawer to fail and blow two thermal fuses after getting hot enough to melt and deform a tub?  I'm at a loss and would appreciate some help here.
Thanks for any advice.

[hutchwilco]

Hi,

sadly my story is very similar - I've repaired and rebuilt my DD603 many times over the years. I have boxes of all the spares I might need. 

However, I my second heater plate fuse in a row just went pop, within minutes of me powering the tub back up.

I was running the motor in drain mode (P2) from the diagnostics menu. I stopped it running and was doing something else when I heard it go pop. I do understand if you leave it in Er (element) mode it'll burn out, but this was in P2 mode sitting idle.

I've tested the element relay on the control board, to see if that has failed closed/short but it hasn't.

So my only conclusion is that the logic part of the element control in the control board has gone bad.

Unfortunately I've also found that the fuses tend to be soldered on to the plate in such a bent way that when they blow, they also vapourise the neighbouring ceramic element, making it harder that just replacing the fuse wire.

I'll update if I find a solution/cause.

 

[J5*]

Afaik the heater plate also sheds load 

if you have a shorted componant elsewhere it can dump power through the heater , it then gets hot and pop it goes 

a trap for young players when replacing a heater plate due to open fuse 

i used to always put my hand on the heater plate in turn on , if it hot too warm then turn the power off 

it does get a littke bit warm at power up due to the leading design 

[hutchwilco]

Thanks, @J5*

I've just come back from actually disassembling again and finding it wasn't the fuse blown - it appears to have been the temperature sensor on the bottom of the PCB connector soldered to the heater plate. Seems a lot of magic smoke has come out based on the black blast marks. It's possible this was due to a small amount of residual water on the under side of the PCB, before I reinstalled.

I've repaired the fuse and tracks on my old heater plate (just scrape back ceramic coating on the heater tracks and solder a strip over the break) and reinstalled.

Indeed as you say, it warmed up very quick after I powered on, so I shut off just as quick. Attached comment on the same cautionary tale- 

Quote

 

AFTER REPLACING A BLOWN HEATER PLATE - ALWAYS CHECK THE PLATE FOR OVERHEATING IMMEDIATELY AFTER POWER ON. TURN OFF QUICKLY IF IT GETS HOT.

A small amount of heat and then cooling a few seconds later is normal at power on.

If it gets hot, you have a bad controller/control board.

 

 

Looks like I have a faulty controller.

 

 

[J5*]

Yep its been a while since ive done a 603 heater plate

dont really get the issue in the later ones

 

603 heater plates are nla well 240v ones are , you might still get them in usa 

but either way now they are pushing 14-20 years old and its not something you really want to get too involved with

 

the safer way with the heater plate would be put water in the tub before turn on as this will give you a lot more time if the controller is stuck on , but it not something i ever did , i always powered on and hand straight onto the plate and you would easily know when it got too hot  

Edited May 16, 2021 by J5*