glow worm swift flow 80 no central heating now?

[typezero]

Hello people,
Basically combi boiler would not heat water up unless i had the c/h switch on,I had this problem for 6 months,then had the flow switch and room stat replaced which then everthing worked for a while.The engineer said I possibly might need a gas valve.Anyway the other day I went to run a bath so I turned the c/h switch on as normal,to get hot water,when all of a sudden rusty brown water came out off the tap,and the combi making some banging noises.What has happened in effect is the problem has reversed it self round,now I can get hot water witout having c/h on.Wondered if anyone out there could help me diagnose the problem.Checked pump spindle turning freeley must be working as I get hot water,But the sympton is every time I try to switch the c/h on,the pressure guage on the combi rises to 3 bar,and makes banging sounds and eventually cuts it self off,therefore no c/h.My question is also do I need a gas valve or is he trying to rip me off was quoted something like £170 for valve + labour.Also the fan unit is working.Cheers Tony

 

[corgiman]

Could still be the pump as the impellers (at the back) may have come off the motor so dont turn, very unlikley though

sounds more like the expansion vessel to me (pressure rising quick and banging then over heating)

I cannot see any reason for a gas valve unless he is totally unsure why this is happening!

Call Gloworm and ask for an approved engineers number and start again is my advice

 

[typezero]

Cheers corgiman,
He has not been out to me yet,he just said about this problem before,that my gas valve is causing the hot water and c/h problem will eventually fail if this makes any sense to you.Also had a new flow switch fitted aswell about 7mnths ago,and room stat.he does not no about this problem yet.Anyway all your advice is appreciated,if anymore please let me know cheers Tony.