VAILLANT 20/1 T3 W WON’T SWITCH OFF

[gorselands]

Back plate on timer and continuity test on timer switch functions all appear good, so still at a loss. No breaks in wires from timer to control box and bridge between 1 & 2 is good.

Mike

 

[The831Bunny]

First of all thanks for staying with me. Tony, I have 2 timers for 2 boilers next to each other. The timer on boiler 1 works fine so I slid it off and swapped it with timer 2. Boiler 2 still did not work so ruled out timer.

The831Bunny I am about to remove the timer as you suggest and see if the boiler fires for heating and will let you know the result. I wasn't aware of a frost stat but have found it on the wiring diagram. Is it a separate box and where is it? I can see it's a switch, is it a relay that could be stuck?

Mike

This test involves being competent to test mains live voltage with a multimeter. The boiler will fire for heating when it receives 230V to T4 as mentioned. Disconnect the wire into T4, test for live at T4 to T5 (neutral) and then the wire end to T5. Each test should be with the heating switch on and clock removed. If T4 is live the fault is within the boiler, if the wire end is live then your external contol wiring is still giving the boiler a voltage to light.

Impossible to say where this voltage is coming from from this end of an iPad... You could have incorrect wiring, a zone valve you don't know about, or a frost stat. How many wires are into terminals 1&3 on the 103 backplate?

 

[The831Bunny]

Back plate on timer and continuity test on timer switch functions all appear good, so still at a loss. No breaks in wires from timer to control box and bridge between 1 & 2 is good.

Mike

Bridge between 1&2????

 

[gorselands]

iPad - that's nice, would save me running up and down the stairs to my steam driven PC.

On closer inspection not a bridge between 1 & 2, black wire feeds from behind top of terminal block into T3.

Cannot think it is incorrect wiring as nothing has been disturbed since working properly. Where is the frost stat and would my boiler have one? Can see it on wiring diag. but no reference to it in Manual.

Will get out the multimeter and write down your instructions to test. I will be back!

 

[gorselands]

Meant to say there is single blue into T1 and single brown into T3.

 

[gorselands]

Wiring into box:- I - 0, II - black, III - 0, 1 - blue, 2 - Brown, 3 - Brown, 4 - blue, 5 - 0, 6 - 0.

230v to 1, disconnected 4 blue zero V, 230v between 2 & 4. Not sure if I have done this right. If not do you have the time to be patient with me and take me through it step by step? T 5 is empty so not quite sure when you say 'test for live at T4 to T5 and then the wire end to T5.

Thanks Mike

 

[gorselands]

About the black wire it goes from top of (behind terminal block) into III, not T3. Sorry for confusing the issue.

 

[The831Bunny]

Ok looks like we are getting somewhere, sorry in the delay, I'm at my boys swimming gala in Thetford today. Lots of waiting around hence the iPad

The black wire at the top of the terminal block controls the pump operation. It should be in I NOT III. III makes the pump run all the time. Swap the wire to I and report back

 

[gorselands]

Thanks for getting back. I have to go out now won't be back till late. I don't think it is the black wire as the other boiler is wired the same and that's ok. What appears to be new is that with the HW switch down (red/white triangle) the boiler seems to flare up from time to time. I can hear it from upstairs. This is with the rad switch off. Maybe it should do. As a rule rad switch is always on. So maybe not noticed it.

Mike

 

[The831Bunny]

Not sure I can upload a schematic of the external controls layout fom my pad, but will do later. If you haven't got a roomstat then your terminal 1 on the 103 clock will go to T4 on the boiler.

Did you test the voltage at T4 at the boiler with the wire removed??? It's the only way to move on. Use one probe of your multimeter (set to Volts) on T4 (wire removed) and the probe to T5. It doesn't matter there's no wire in it, it's a Neutral to test to.

I can't really tell you much more until you return with facts. If you are fault finding its a process of logical ilimination, and proving what is and what is not! You can't rely on "didn't do it befores" or "the other ones the same"

 

[gorselands]

Thanks for getting back. Hope you enjoyed the gala. First apologies, the black wire goes to II not III as I previously said; this has not been disturbed.

Voltage from T4 (wire removed) to T5 is reading 228 volts.

Your help much appreciated. I have to go out again but will check in tomorrow. No room stat fitted.

Mike

 

[Bunnyman]

Hi mate 831 doin a good job as usual! If u have removed wire from t4 an tested from the tip of that wire to t5 an u have 240v then if the clock is still off it's backplate u have a voltage externally coming from somewhere u shouldn't have, if nothing has been altered u r looking for an external frost stat somewhere or if it's a big system have u a zone valve somewhere?
If however u have 240v at t4 (with wire removed ) then that's a boiler fault, have u had any water down the flue recently with the rain? This model suffered these probs if water ran down the front into where the switchers are

 

[The831Bunny]

Just a thought Bunnyman, like you said earlier, water section switches stuck on, flow switch rises, breaks S1. Boiler set to PPII, boiler sits there for a while with pump off, and thats when OP thinks its all OK. Makes more sense to me than a stray voltage to T4.

 

[gorselands]

Thanks both of you. Reading the posts have done voltage tests again with timer removed and from wire end.

T4 to T5 - 233 V

T4 (wire end) to T5 97 volts.


Rad switch on, HW r/w triangle down, boiler fires up with T4 removed.

Made a rapid 'tocking' sound for few secs on start up, stopped when boiler flamed. Heard it last night but maybe put it down to switching boiler on/off so often had confused something. Sounds a bit mechanical but then thought it could be air. Don't know. Had the stethascope out (long screwdriver to ear) seemed to be coming from control box.

Thanks Mike

 

[Bunnyman]

Definitely boiler prob then so reconnect timer etc, the machine gun sound ( as we call it) is a red herring change the red 3 tag micro switch on the solenoid right in front of u in the middle. That will stop that but that won't make the boiler stay on . I still think its the water section stuck