Vaillant ecotec plus 438 no heating or hot water

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Morning all,

Heating was left on last night, and hot water came on at 7 to 8 am and now I can't get either hot water or heating to work. The pump does work however as I have done the pump test from the boiler.

Can the 3 port valve be faulty? But in any case the heating or hot water should kick in.

Had a powerflush last month.
 
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More likely to be a boiler component ,or control issue. Can you measure voltages safely at the wiring centre ?
 
More likely to be a boiler component ,or control issue. Can you measure voltages safely at the wiring centre ?
Well I was about to, went to pick up a multimeter and a replacement valve head to save a second trip and when I came home the heating had been on an for an hour.

I've put it on to all day.

Heating was on all day and that's what the programmer was showing this morning.

Do you think it could be the programmer? It's 15 years old
 
It could be any number of things. When all is working its nigh on impossible to establish the reason it didn't work. When it stops working ,it's a process of elimination be establishing voltages present ( or rather a lack of them ) at given points.
 
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It could be any number of things. When all is working its nigh on impossible to establish the reason it didn't work. When it stops working ,it's a process of elimination be establishing voltages present ( or rather a lack of them ) at given points.
Many thanks.

Am I right in saying to test whether the programmer has live, this will be done by opening the programmer or will there be a live in the junction box in the loft where the wires for the pump and valve are?

Obviously to test whether the 3 port valve is getting 240v this will be done at the junction box.

Would you test for continuity between programmer and 3 port valve or does the receives 240v when the programmer is turned on?
 
Testing would be done at the wiring centre / junction box. You would need to study a wiring diagram for Y plan ( system with 3 port valve).
If you set programmer for domestic hot water only,the programmer sends voltage to hot water cylinders thermostat, which if not satisfied ( water isnt hot and needs heating),the stat sends voltage to the terminal that boilers switch wire connects to and energises the boiler to fire up. If boiler isn't firing ,you establish where the loss of voltage is.
It's a bit more complicated with the central heating part of the system.
 
Testing would be done at the wiring centre / junction box. You would need to study a wiring diagram for Y plan ( system with 3 port valve).
If you set programmer for domestic hot water only,the programmer sends voltage to hot water cylinders thermostat, which if not satisfied ( water isnt hot and needs heating),the stat sends voltage to the terminal that boilers switch wire connects to and energises the boiler to fire up. If boiler isn't firing ,you establish where the loss of voltage is.
It's a bit more complicated with the central heating part of the system.
Many thanks.

The problem happened again today and it worked again.

The boiler didn't fire up for neither heating or water.

Does the pump kick in first or do the relevant stat tells the pump to kick in / boiler fire up?
 
For instance , with Programmer selected heating only...
Programmer sends voltage to heating thermostat.if stat isn't satisfied it sends voltage to motorised valves motor. Motor turns and opens gate in pipework to allow water from boiler to flow to radiators,and triggers a microswitch within the valve. The microswitch sends voltage to boiler and pump which both spring into life.
In very basic terms that's the sequence.
 
For instance , with Programmer selected heating only...
Programmer sends voltage to heating thermostat.if stat isn't satisfied it sends voltage to motorised valves motor. Motor turns and opens gate in pipework to allow water from boiler to flow to radiators,and triggers a microswitch within the valve. The microswitch sends voltage to boiler and pump which both spring into life.
In very basic terms that's the sequence.

More games! Heating was on all day, put water on for an hour and heating gone off as well.

Now neither come on.

Getting 240v.

Changed the valve head and same problem persists
 
Last edited:
What programmer and central heating thermostat do you have ?
Getting 240 volts doesn't tell us anything unless we know where you are measuring ,and at what programmer setting etc
Show us pics of wiring at the wiring centres terminals.
 
At the grey and orange wire terminals at the valve (for the cylinder stat) was getting 170v rather than 240v. This was when the water was off.

The green cable from the valve to the white cable was getting 240v when heating was on.

Heating was set to permanent on.

Siemens RWB9 programmer and salus rt310 stat.
 

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With programmer set for central heating only to be on ( domestic hot water off),and the central heating thermostat set to maximum ( calling for heat) ,measure the voltage between the terminal that contains the orange wire ,and the earth terminal( far left hand terminal) You should get 230/240 volts. Do you ?
 
With programmer set for central heating only to be on ( domestic hot water off),and the central heating thermostat set to maximum ( calling for heat) ,measure the voltage between the terminal that contains the orange wire ,and the earth terminal( far left hand terminal) You should get 230/240 volts. Do you ?
Do you mean the earth and the red wire (above the brown)? The brown is for pump.

I did get 240v at the brown and one of the neutrals.

It has started working again with the new head installed. I may have put one of the wires inside a terminal too much and the sheeting got screwed in rather than the copper.
 
thermistor needs replacing. I'd take any bets on that being the fault
 
The orange wire from the motorised valve ( in the 5th terminal, from the right hand side) Is what sends voltage to the boiler via that terminal. So ,when only c/ heating is called for That orange wire should have 230/240 volts ,measuring between it and earth.
 

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