Nope, the selector switch works perfectly.
Here's a load of other stuff I've tried to no avail:
Any advice would be greatly welcome.
I know that the central heating thermostat knob potentiometer thing on the front works because i've unsoldered it and the hot water one and tested them with a multimeter and they both work. I've even swapped them round (they are identical don't worry) and the hot water works fine, but still no central heating.
There is no roomstat. The timeclock works fine. I've checked it for power and continuity with a multimeter.
I've checked the resistance of the thermostats. They are both cold so the comparison is fair. Central Heating is at 23.83 k and hot water at 23.98 k. Also checked the safety thermostat that is just below the CH temp sensor and that measures 0.03 ohms.
Somebody on another forum suggested I check the microswitches and they work. Also I took them off and you can see the valve shafts going in and out when calling for hot water or when preheating hot water. Both microswitches work. Also when I poke the switches the hot water comes on, but again nothing as far as CH is concerned.
I swapped the thermistors like somebody on another forum suggested and still the same problem. I was going to say that the hot water thermistor must be ok, but I don't know if it is. I turned on the preheat on minimum (turned the potentiometer just enough so that it would switch on) and the temp kept going up to 70C and probably would have gone higher if I let it, but I switched it off at the point. Surely if it's at minimum, it should have only gone up to something like 30C or 40C?
Also something interesting has just happened. I've put the thermistors and everything else back how they were originally, switched the selector switch to hot water only, turned up the potentiometer to max, while the water was warming up I turned the central heating potentiometer up to max and switched the clock to always on, let it get up to 70C or so, then turned the preheat hot water potentiometer to minimum, the heating then stopped and then I turned the selector switch to both hot water and central heating. The pump kicked in, the CH light came on briefly for half a second, the pressure went up from 1 bar to 1.5 bar just like if the ch was working, and the temp went down wery quickly, so the cold water in the radiators must have been circulating through the boiler at that point because the temp went down v quicklly and cooled it down, and of course becayse the pressure went up. Still, no indicator light and no flame.
I've had to bring someone to look at it because it's getting pretty cold.
They said it's the diverter valve, and the diaphragm and that they need to replace the whole of the diverter valve assembly and that it would cost £250 with parts and labour.
Believe me when I say I don't like to cut corners. When I do something I'd rather pay a bit more and get it done right, you know? And I understand they need to make a living just like any of us, but, the problem is that I can't afford it. I though it would be expensive, and hence why I'm here asking for help and advice from you guys in order to try and get a fair price for the parts and labour by finding out what's wrong how much it should cost.
Would they really need to change the whole of the diverter valve part? Can't they take it apart and change the faulty part? Or if it is just the diaphragm (which they conveniently wouldn't say, and said 'it's both'). I've seen diverter valves for £87 (unsure if it's the complete assembly) and rubber diaphragms for £3 on ebay! Also he wouldn't say how much it was just for the labour, he would only give an all inclusive price.
I've done some deduction logic, and I don't think it's any of the diaphragms nor the diverter valve, and neither is the CH thermostat. Most likely the PCB.
My logic is this:
When the hot water taps come on, the diaphragm pushes the microswitch, and the circuit is completed.
When the preheat comes on, the other diaphragm puses the other microswitch and that circuit is completed, so surely that means that both diaphragms and microswitches work. I've tested them by pushing something in the microswitches and the same thing happens, no CH.
I've taken the operating head (the motor) off the top of the diverter valve. It works because I can see the metal pin going in and out. Also I've put my finger in the top of the diverter valve and pressed the pin in there. It moves, so it's not ceased.
After putting the operating head back on I've done the trick I mentioned earlier (I switched the selector switch to hot water only, turned up the potentiometer to max, while the water was warming up I turned the central heating potentiometer up to max and switched the clock to always on, then turned the preheat hot water potentiometer to minimum, the heating then stopped and then I turned the selector switch to both hot water AND central heating and the pump kicked in, the CH light came on briefly for half a second, the pressure went up from 1 bar to 2.0 bar just like if the CH was working, and the temp went down very quickly, so the cold water in the radiators must have been circulating through the boiler at that point because the temp went down v quicklly and cooled it down, and of course because the pressure went up and because when I do this with the operating head off I can see the pin moving to open the valve. So, the diverter valve defintely works!
Now, I've swapped the contacts of the CH and hot water thermostats around and the same thing happens. I know the hot water thermostat works because it turns the hot water off when it reaches temperature, so the thrmostats work, and besides, if they didn't, it would show up as a fault on the status lights.
Correct me if I'm wrong, but the only thing that is left, is the PCB.
What do you think guys?
