How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask bonzaco Your Own Question
Category: HVAC
Satisfied Customers: 1386
Experience:  Owner at Dales Electronic
Type Your HVAC Question Here...
bonzaco is online now
A new question is answered every 9 seconds

GB 142----Fault code 3C----217 ?????

Customer Question

GB 142----Fault code 3C----217 ?????
Submitted: 5 months ago.
Category: HVAC
Expert:  Phil replied 5 months ago.


Click here for the manual and error code / recommendation charts

They do not list a 3C--- or 217 code.... older model data does not always show up in current model literature.

That said, the chances that this is something you can repair yourself are in the 1 to 2% range, these are very sophisticated systems, even the less experienced or newer Buderus dealers have a great deal of trouble getting a diagnosis and repair.

If you can tell me how the system is behaving, working or not working and which direction and distance you are from the center of the nearest city I can be more specific.

Customer: replied 5 months ago.
The system will not come on---will not show a ignition...It shows in the display on the BC10----72 and when I push the rest it show P19 and the after a few minutes it shows 3C 217....I've checked the flu outside-it looks ok....I installed it myself and it has worked great for the last 12 years....This is the first real no work time....
Expert:  Phil replied 5 months ago.

Good work on the install!

Repairs of the electronics related items on board, can be a lot more complex however.

Lets do this test:

The boiler may be failing somewhere in the ignition sequence, this test will tell me where it is failing, and I will know from that what component we need to test.

Stand next to the furnace after the thermostat has been turned off for 5 minutes. Listen intently as someone else turns the thermostat to heat and sets it for 85F.

You should hear the small inducer fan start right away.. then a faint click after 1 to 3 seconds, that is the pressure switch closing.

....then in 15to 45 seconds you should hear 2 more faint clicks, that is the ignition relay and gas valve relay closing.

....then within 5seconds you should hear the main burner fire..

In about 30seconds the main blower should come on.


If the main burner goes off after 2 to 5 seconds or within a minute or so tell me about it and the number of seconds involved.

Repeat that a few times until you get familiar with the sounds, then tell me in detail how far the sequence goes before it stops.


Tell me please if this is identical to the wiring diagram glued to the inside service panel of your unit or not.

If it is, I can mark it up with trouble shooting instructions.

Customer: replied 5 months ago.
I'm going to hang it up for the night--have a beer and look at things tomorrow----Thanks---I'll do as you asked with the turning on and off....
Expert:  Phil replied 5 months ago.

Good idea, I will be here all day tomorrow as well.

Customer: replied 5 months ago.
Okay----I've found the error code on Bosch--has to do with the fan...So checked the fan--it turns and is not running as fast as I would think when the boiler is working.....When there is a demand for heat, the led on the BC 10 on the right side comes on--I look in the sight mirror and can see the glow in there--no flames....I checked the power to the gas value---no power to the 3 wires in the combo they talk about in the manual.....So I look at the UBA3---when I shut the furnace down--the red light in the corn comes on for a shot time--seconds....Pulled the UBA apart and check the little round transformer---primary has resistance---sec is open...So looks like it is the UBA??????
Expert:  Phil replied 5 months ago.

Superb work!

can you mark 'little round transformer' that you found in the UBA3 on the wiring diagram and tell me again if this is identical to the diagram glued inside the front panel on your boiler?

we can go from there.

Customer: replied 5 months ago.
The diagram is the same as in the book, and shows the transformer.....I had friends stop by, so have'nt screwed with the thing....Will look at the mess tomorrow....trying to find out more about the transformer, I would think the input would be 120 and the output would be 12 volts, no centertap and is bridged rectfied , so that would double the voltage to 24 and then filtered...I'm thinking about mounting a outboard transformer---12 volt and running the 4 leads in through the back and hooking them up....I don't feel like spending $500.00.......
Expert:  Phil replied 5 months ago.

confirm that we are talking about the same items please.

We can go from there.

Customer: replied 5 months ago.
I'm talking about the buderus gd142 that had a error code of 3c-217 that you didn't know anything about.....OKAY
Expert:  bonzaco replied 5 months ago.

Good day my name is ***** ***** Im here to help you today. Error 3C-217 is a bad tachometer in the combustion motor - from memory I think it comes as a new complete motor and tacho (I'm fairly sure it does). I would replace them both if they come seperately.

Would you now kindly rate the information given by selecting from the star rating at the top of the page. Thank you for using JA and have a great day.

Related HVAC Questions