HeaterMeter fan not working


 
N

Nick_B

New member
Now that I have some spare time I decided to make a couple microdampers. The problem came when I hooked the second one up to the heatermeter and the servo worked fine but the fan wasnt working, and then I noticed a slight burnt electrical smell coming from the heatermeter. I unplugged everything right away and luckily everything seems to be still working on the heatermeter except the fan, touching ground and blow on the board with a multimeter is 0 when I think it should have power. The burnt smell is coming from right around the rj45 plug the damper plugs into. I am looking for some advice on where to start trouble shooting the problem. The weird part is I wired this microdamper exactly the same as another one I have and a adapt a damper that both worked fine.

Fan/servo black to Blue
Fan red to blue/white
Servo red to green/white
Servo yellow to green
 
Did a little more testing, does power for the fan come from A or B in the picture? Or maybe neither? I have power at the arrows but not at the yellow x's. It looks like C and D is a capacitor, is it possible I fried that one, I feel like one side should have power? Is it possible to test a capacitor? I am hoping I don't have to replace the whole board.

hm2.jpg
 
The blower's power comes from the big MOSFET on the top, you should see 12V up there on the left two legs, and a lower voltage on the right leg (at 100% output). The voltage diagram might be helpful in debugging:
HeaterMeter434BaseV.png


If the left one has 12V, and the right one has some higher voltage, but nothing on the center pin, then your MOSFET is dead. If the left has 12V and the right has 12V, then the driver MOSFET Q1 is your likely culprit.
 
Thanks Bryan. Due to my clumsy hands I touched the wrong thing and now I have power nowhere. I will be ordering a new one when store reopens, and will leave the cover on next time.
 
Doh! If you start from the 12V input and follow the red line to the diode, then to the capacitor then to the 5V regulator module does it follow through? It might just be the diode is blown. The 5V regulator tends to be somewhat robust so it should shut down in case of a short and then come right back.

Also check the power supply without it being plugged in to make sure that's ok. If it gives 12V when not plugged into the HeaterMeter, and turns off when plugged in, that just means short circuit prevention is kicking in and there's just a component on the HeaterMeter shorted (which you can also check without power plugged in and measuring the resistance between the two GND and 12V pads on the power jack). Finally check between 5V and GND anywhere on the board and make sure there's no short circuit there too.
 
Thanks again for replying. So if I follow the red line up to what looks like D something and beyond I have nothing, but I do have 12V if I follow the red line to the right to what looks like JK and alarm.
 
Oh that's good news I think, because it sounds like you've just burned out that diode. If you're saying that following the red line, you get voltage at one side of the black diode but not the other, you can try just jumpering over it with a bit of wire to see if it gets you back in business. It is just a protection diode so you can run without it with the wire in place until you replace it, if you decide to replace it.
 
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