Replacing the Fan on a Buderus GB142 boiler

Discussion in 'Tutorials' started by jadnashua, Oct 31, 2017.

  1. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    I awoke over the weekend with a boiler failure and trouble shot it to a failed fan was getting power, but not running. The display showed a 3L 214 error code, which meant that there was no fan (thus no gas to burn) and the system had gone into lockdown. My indirect is fairly large, and for the next two days was able to take a couple of quick, but only warm showers. Did my laundry in cold verses warm. On Monday, checked with the local supply houses, and they all said they could get one in a day...not being a pro, their prices retail were higher than I could find it on the web, and since I could get one cheaper, free shipping, for less, in a day, I opted to order it on the web. It showed up this morning, and it took only about 20-minutes to install. I'm waiting for the indirect to get hot, then take a long soaking bath that my back will appreciate. In the process, I found that the instructions in the maintenance manual left out a few steps that I had to figure out.

    1. The instructions call for removing a screw on the burner assembly to remove the fan...on mine, it was a 5/16" nut on a stud. No big deal (it might be metric, but a 5/16" socket worked).

    2. To remove the plug on the bottom, you have to press in on the latch so you can slide it out.

    3. You have to remove the control plug on the gas valve assembly in order to have enough freedom of motion to remove the fan assembly.

    4. The gas valve assembly is attached to the fan...the instructions don't say anything about removing that! There are three screws. Note, when replacing it on the new fan, do the end one first, then the two that are vertical, or it might be tipped enough so you can't get the end one in. I think that's because of the gasket needing to be compressed.

    5. The instructions say to turn the fan to the right, but what may be clearer, would be to rotate it clockwise when looking at the front of it. The left hand section has a taper on it so you can do that. That will allow the right-hand side to dip down enough to clear the alignment pins, so you can then slide it to the right and get the left-hand side clear.

    4. You have to remove the venturi assembly from the fan. It isn't (or wasn't to me!) obvious, but first, you slide the clips away from the end (I pried them off, and luckily, they didn't break). Then, you can pry lightly on the hooked shape arms that lock the thing into the fan, then pull it out. Replacement on the new fan is just the reverse...slide it in until the locking tabs are in place, then slide the clips back onto the fan to lock it in place.

    That's it. Doesn't take long - took me maybe 20-minutes. Turned the boiler back on, and it fired right up. Note, when trying to check the 120vac to the fan motor on the plug, the pins are quite small and narrow...a typical meter probe won't fit, so I used some common straight pins from the sewing room to slide in there so I could measure the voltage...when I found that was there and the motor didn't turn, that pretty much told me the fan was toast. In the process, sometimes, the error code was 3Y, which said the tachometer showed the fan was running too fast, but that stopped after awhile, and it only showed 3L. The tach is part of the fan assembly. I ended up using a small mirror to replace that plug, since it is on the bottom, and not that easy to see to get the plug aligned so you can slide it in and lock it.

    Hope this helps...if you're at least a little handy, this is an easy repair and got me heat and hot water back in a pinch. Since you're touching the gas valve, but not opening or adjusting it, there still is some potential for error. I take no responsibility if you damage something or yourself, but at least in my case, I found it quick and easy to do this task. I have the guys coming soon to do a tuneup/cleaning, so since the fan was changed, they might have to tweak the gas/air mixture, but that's all part of the service routine. In theory, it should be okay, but may not be optimum. I don't own an exhaust gas analyzer, so that's best left to a pro who does and knows how to use it! Maybe next time I'll buy one, but not sure about the cost/benefit for something I wouldn't use often, then, how to keep it in calibration...humm...I'll have to think about it.

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