Vaillant combi-boiler and no CH?

Hi, as John has said, LINKS 3&4 need to be linked, either via a room stat or a piece of wire.

Since you are getting hot water I would first of all rule faulty ntc's (boiler stats). What you are describing sounds like a faulty diverter valve, possibly stuck in hot water mode. Or it may be an electrical fault, such as a bad connection to the diverter valve for example or even the pcb. Try looking at this first. If this is not the fault then as the boiler is under warranty, since you say it is less than a year old,then get Vaillant to look at it.

Having said all this, you say there is no error code which is strange and suggests that there may not be any fault at all with the boiler and that there is no call for central heating. If the wireless stat is not connected, then check the terminal block where the mains cable is connected to the boiler. You should have live neutral and earth. Next to this you should see connections 3 & 4 which should have a link wire connecting them together. If there is no link wire install one. If there is a link wire check for lose connections.

On another note you say the pressure in the system is 3psi. Do you really mean 3 BAR. If so this is much to high and should be reduced to between 1 and 11/2 bar when cold.

Vaillant Boiler Not Working

Try turning the CH dial down. The influx of heat when it kicks in may trip any thermostats into shutting down because the temperature is too high.

Vaillants are good boilers, so if there is no error message then it's most likely a component fault like pumps or motorised valves.

The cold pressure is too high. Reduce it to 1.5 bar by either opening the safety valve or a bleed valve on a rad. If it is still under guarantee and the installer can't sort in straightaway ask Vaillant UK if they can send one of their own engineers. These big firms are usually very helpful when it comes to boilers under guarantee.

I've got the same boiler, (5 yrs old) but the opposite problem, water is leaking slowly out of the system and every few weeks we have to let more water in. Assuming you haven't had it serviced in a while, I think that's what you'd better do. Vaillant are quite good, they charge about £100, but you can check with them before you book the appt. I think you're right about it not being a good thing.

As there is no prob with HW. First test the CH system -motorised valves and pump(s).

If no luck then look at boiler.

If your boiler is under 1 year old it should still be under warranty. Contact the person who installed it or call Vaillant.

http://www.vaillant.co.uk/contact-1/