Stoves Q900 GRF DO fan assisted gas double oven

I know it's been a while but I had the same problem with my one of these. I initially suspected the 2u2 capacitor on the main PCB as it forms part of a transformerless power supply for the board and this has been the cause of so many of our household appliances failing but as it turned out, not in this case.

For some reason my attention was drawn to the pressure differential switch assy. I blew air into the port open to the inside of the cabinet and I could hear it click but instead of a short circuit, the switch terminals showed a resistance of around 400 ohms.

I decided to remove the micro switch from the diaphragm unit (means drilling off the ends of the rivets) and the switch itself then came apart easily. The contacts could then be easily cleaned with a 'scotch cloth' and provided the rivets aren't too badly damaged they can be reused to remount the switch when put back together.

For me this dropped the resistance from around 400 ohms to about 0.5 ohms which is only just above the datasheet spec of 300 milli-ohms.

Once the oven cabinet was rebuilt (necessary to operate the pressure switch) the oven then worked perfectly (so far and fingers crossed) which considering we can't find a replacement LPG double oven to fill the 900mm high cavity the old one sits in, is a bit of a god-send.

I did find a supplier on aliexpress.com who could supply the microswitch (part no V5610R-041) but only in quantities of 5 for US$100 which means it's probably better all round to replace the entire differential pressure diaphragm assy.

I hope this helps someone else and I apologize if this has been abit of a ramble

SixFingersMike

Hi everyone, i hope this helps.
you may need to take the oven out and use a vacuum cleaner to **** out the dust from the back of the oven, i found that this is the cause for ovens not lighting and grill not working, its a simple thing to do, just pull the oven out and at the back you will see where all th dust has accumulated, just vacuum it out
and it should work. i have had so many problems that i am going to replace the whole piece of **** now that the fans have packed up !
stoves know that the ovens are rubbish and unreliable, but have done nothing to help (even the engineers know this)

Good answers, but vacuuming the inside is, I think, just a temporary fix, but does point to the differential pressure switch needing replacement due to stiffening of the internal diaphragm and/or (as pointed out earlier) trouble with the microswitch contacts. Cleaning out the dust and cleaning the fan blades probably leads to a slight increase in internal pressure causing the switch to work again for a while, but ultimately the switch will need replacing.

Looking at the circuit diagram for the oven, only two things can cause both ovens and the grill not to light; the differential pressure switch and the main circuit board. As a new main board costs over 500 pounds and the pressure switch costs about 50 pounds, try the pressure switch first :).

Be aware that spare parts are now difficult to get, but fortunately I bought a 2nd hand oven in a clearance sale for 90 pounds about 4 years ago, so should be OK for parts like fan motors, etc. and hopefully will keep the oven going for the next 20 years.