Hi
As this site has helped me keep my Vaillant VCW 242 Combi Boiler going for the last 20 plus years without an engineer callout, I thought I better share my latest fault and repair finding with anyone who still has one these comi's.
So here's what happened.
The boiler appeared to be working fine supplying hot water and heating as normal. However it didn't sound quite correct (sad, I know but I've had it a long time) It appeared to be making sort of sluggish hissing before the burner shut down each time, when I checked the temperature gauge on the unit I was a bit concerned to see it heading into the 90 degree plus area even with the boiler setting to number 6 which normally is about 70 to 75C.
Turning the controller down did not seem to have any effect at all, the flame stayed at maximum height and did not modulate down as it should have done when the knob was turned down.
As the domestic hot water was working fine I suspected the diverter valve was stuck in this position. Taking the boiler cover off and looking at the diverter diaphragm actuator rod (that pushes the micro switches) it was clear that the rod was sticking and it had some calcium around the valve. Stripping the micros witches off, the area was cleaned and some light release oil sprayed on. The rod was pushed in and allowed to spring back out a few times. Although the rod did feel somewhat lumpy when pushed back in, suggesting some internal wear.
Reassembly with the covers off, the boiler was fired up and with CH on the rod retracted in as it should do and turning down the temperature reduced the flame height until the it switched off. With CH on and killing the system with the on off switch on the boiler also operates the diverter valve from fully in to fully out which is a good test for the system.
So its now working and the diverter has gone from just failing probably to just working.
Next step is to order and fit a replacement diverter. This will be the first for this boiler so I can't complain.
Hopefully someone may find this useful in repairing their boiler.
As this site has helped me keep my Vaillant VCW 242 Combi Boiler going for the last 20 plus years without an engineer callout, I thought I better share my latest fault and repair finding with anyone who still has one these comi's.
So here's what happened.
The boiler appeared to be working fine supplying hot water and heating as normal. However it didn't sound quite correct (sad, I know but I've had it a long time) It appeared to be making sort of sluggish hissing before the burner shut down each time, when I checked the temperature gauge on the unit I was a bit concerned to see it heading into the 90 degree plus area even with the boiler setting to number 6 which normally is about 70 to 75C.
Turning the controller down did not seem to have any effect at all, the flame stayed at maximum height and did not modulate down as it should have done when the knob was turned down.
As the domestic hot water was working fine I suspected the diverter valve was stuck in this position. Taking the boiler cover off and looking at the diverter diaphragm actuator rod (that pushes the micro switches) it was clear that the rod was sticking and it had some calcium around the valve. Stripping the micros witches off, the area was cleaned and some light release oil sprayed on. The rod was pushed in and allowed to spring back out a few times. Although the rod did feel somewhat lumpy when pushed back in, suggesting some internal wear.
Reassembly with the covers off, the boiler was fired up and with CH on the rod retracted in as it should do and turning down the temperature reduced the flame height until the it switched off. With CH on and killing the system with the on off switch on the boiler also operates the diverter valve from fully in to fully out which is a good test for the system.
So its now working and the diverter has gone from just failing probably to just working.
Next step is to order and fit a replacement diverter. This will be the first for this boiler so I can't complain.
Hopefully someone may find this useful in repairing their boiler.
