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Michael, Customer Service
Category: Appliance
Satisfied Customers: 9568
Experience:  I have been an appliance repair tech for over 30 years and will help you solve your problems.
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Got a siemens RCR 10/433 boiler control unit. At the moment,

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Got a siemens RCR 10/433 boiler control unit.

At the moment, does not seem to be working and therefore our heating is not working. We can get hot water, but no central heating :-(

Press the reset button and it flashes red for a few seconds, but no green light.

Have tried adjusting the thermostat unit to a low setting and then increasing it again in the hope of kick starting it - no joy
I am Tech Michael and I will be assisting you today.
Please be patient with us as these are technical questions and some testing may be required.
It may take a bit of back and forth conversation to be sure we have all the information in order to make a proper diagnosis.
How old is the control unit?
Also who installed it and did it work at all after installation?
Please let me know all about this in detail so I can help you.
Thank you
Tech Michael
Customer: replied 4 years ago.

Boiler installed Nov 08, and I think this unit was probably installed at the same time, so a bit over 5 years


Yes, been working reliably until last few weeks when it has been a bit temperamental. Since two days ago, nothing


Thank you for that information Andy.
This is one of two things here, either the boiler is in need of basic cleaning and maintenance. Especially if its been over 2 years since that was serviced.
If that hasn't happened then the control unit itself would need to be replaced.
I will stick with you until this is working as it should, please keep me informed;-)
Since this may take some time, if you will rate my service in a positive fashion thus far before you close this page, the system will allow me to schedule free follow ups with you and also ensure your question will NOT close or time out;-)
You will then be able to contact me at anytime at no additional cost until we have this fixed for you.
Thank you Andy.
Tech Michael

Customer: replied 4 years ago.

Boiler serviced a couple of weeks ago. Boiler working okay

Customer: replied 4 years ago.

What is the other thing you think it could be?


Thanks Andy,
This may very well be only the flame sensor.
That would definitely cause this and as for the control boards, they can always fail without warning, but they are usually very reliable with these. Also there really isn't much else that would cause this problem.
I would have the tech come back, as this could be a bad sensor or an air adjustment is all.
I will stick with you but please rate kindly so I can set up the free follow ups for you.
Thanks Andy.
Tech Michael
Customer: replied 4 years ago.

Are there any test buttons on the back of the transmitter that can be used to try and reactivate it?

Hi Andy unfortunately there are no rest buttons.
If your Thermostat has batteries, I would replace them with known good ones, but before doing that you should install them in the verse direction and let it sit 2 full minutes, then replace them correctly and try that.
Please let em know.
Thanks Andy.
Tech Michael
Customer: replied 4 years ago.

Tried that already... :-(


Are we looking at a unit replacement then?

Hi Andy of you already did all that, it sounds like its time for a new controller.
I wish I had better news for you I really do, but at least you know for sure what the problem is.
I wills tick with you so if you have any further questions please ask me.
If I have been helpful please rate kindly before closing this window, I will schedule free follow ups for you.
Also if you are a little handy and have some basic tools I can help you do this without the added cost of a Technician.
Thank you Andy.
Tech Michael
Customer: replied 4 years ago.

you are giving conflicting advice. Which should I do?


You say "I would have the tech come back, as this could be a bad sensor or an air adjustment is all".


You also say "it sounds like its time for a new controller.
I wish I had better news for you I really do, but at least you know for sure what the problem is".

Hi Andy,
no thats not what I am saying sorry for the confusion.
I said that , until you mentioned you already tried my suggestions.
In this case the controller does need to be replaced as there are no user serviceable parts inside, unfortunately they don't sell parts for the controller.
But you could make the replacement yourself, with my help if you have the basic tools and a bit of handiness.
Or, if you don't wish to do this repair yourself, just as a tech to come replace that part for you.
Either way I will work with you.
I hope that helps clear this up?
Thank you
Tech Michael

Customer: replied 4 years ago.

Mmm...what did we do to test for a bad (flame) sensor or air adjustment? How have you now ruled out these possibilities?


If you think the only option now (apart from a whole new unit) is to make a replacement part, what replacement would I need to make and with what materials?

Hi Andy, do you have a meter for testing?
If so we could go further in that direction.
But if you don't want to do all that, the part that needs to be replaced is either the flame sensor(very inexpensive) or the control board at the boiler, please let me know what you would like to do I will help any way I can.
Thank you
Tech Michael
Customer: replied 4 years ago.

The boiler was serviced a couple of weeks ago, so I don't suppose the control board at the boiler needs attention.


I don't know (and you have not said) where the flame sensor is - is this part of the siemens unit or part of the boiler? If part of the boiler, I suspect it should be okay (as boiler serviced recently). If part of the siemens unit, can you be precise about what I need, where I might get it and what I do with it once I've got it?


I simply do not understand what you mean when you ask, 'do you have a meter for testing?' Is that a piece of kit to test something on the boiler or the siemens unit?

Thanks Andy for your patience as this is a technical issue,
Just to be sure of whats going on with the flame sensor and the control board please do this first and let me know if it helps at all or what happens.
1. Make sure the thermostat unit has its vertical switch set to 'run' and the horizontal switch set to 'auto'.
2. Loosen the screw holding the thermostat to the wall (situated underneath, just loosen the screw don't take it all the way out). take the unit to the boiler.
3. On the wall unit/receiving unit next to your boiler there are two buttons 'Set' and 'Reset'. press and hold the reset button for 4 secs until orange light starts to flash
4. Then press the 'Set' button on the same unit (the light should flash again.)
5. Press the 'Learn button on the back of the thermostat unit try to be a good meter away from the wall unit /boiler. the lights should flash and then turn green
6. Press the 'test' button on the back of the thermostat. This sends a test signal to the boiler . the green light should come on again. when this has happened press the test button again to switch off the test signal.
This should now work
Customer: replied 4 years ago.

Right. Tried that.


Green light on Siemens unit now solid green. Yellow light gone out. But no sign of life from the boiler :-(


Please, what does this tell us?

Thanks Andy,
This tells me the board is bad and needs to be replaced, the main board.
Did you need a source for that or are you going to let a repair tech do this for you?

Tech Michael
Customer: replied 4 years ago.

Okay, so this is the control board that is part of the boiler, right?

If so, should the servicing guy have picked this up 2 weeks ago?

Does this mean that the siemens thermostat unit is okay and not in need of replacement?

How much should I expect to pay for a control board?

Are they easy to get hold of?

Is it easy to replace?

Could I do it myself, or should I get the servicing guy to come back and do it?

Hi Andy, he should have check this, but this could have just failed as all electronics can.
If you have some basic electrical knowledge and the tools I can help you get the part and assist you with the replacement.
I would contact Espares fro this part.
See if they still have one in stock, you will save money if you order the part even if you decide to have a tech install it. I don't recommend doing this if you don't have the appropriate experience as you could do more ham than good.Please call:

0844 9777 888

Monday to Friday 8am to 6pm, Saturday 9am to 4pm, or 10am to 4pm on Bank Holidays

For security and training purposes, telephone calls may be recorded or monitored.

Outside the UK? Call us on: +44 (0) 20 7717 5046.

Customer: replied 4 years ago.

Can you please tell me precisely what part I need to order (order ref or code?) and how much I should expect to pay for it? Thanks


I might well get the guy back to install it...


In case it is relevant, the boiler is a Ferroli Optimax HE31S

Hi I don't have the model code, espares can help you with that as different shops have different #'s and also it sounds like you would be better off having the tech back in, because I will bet the board is bad, it is called main control board. But it could be only the flame sensor, although I don't think so.
One last thing you could try is to be sure you do have power at the boiler controls on the boiler.
I wish I could be more help but I have told you the best option on this.
If you have a multimeter and want to do some testing I will surely help you there;-)
Thank you
Tech Michael

Customer: replied 4 years ago.

This is a boiler part, right (Ferroli)? Not a thermostat part (Siemens)?

Hi Andy thats correct.
Its a boiler part. But its the electronic control.
It supplies power to the boiler and the entire system;-)
Hopefully that helps!
Thank you Tech Mike

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