I recently replaced my Vortex single-speed vent fan with the Vortex II multi-speed reversible fan. While installing the fan, I accidentally dropped the fan on to a soft bed. I was surprised to find that the fan had broken where one of the resistors was mounted to the printed circuit board.
The problem is that the big, heavy ceramic resistors are just soldered to the circuit board with no support.
Luckily, I am in the aviation electronics business, so it was no problem to repair the broken solder joint on the resistor, but I also realized that preventing future failures was a simple matter of under-filling the resistors. Components in aviation electronics are usually under-filled with epoxy to provide structural support to improve reliability. Wherever you can eliminate movement between components, you eliminate the possibility of stress fracturing.
To help prevent future failures in my fan, I under-filled the resistors with silicone caulk. This should prevent movement that will lead to cracking. Epoxy might have been a better choice, but would have been much more difficult to install into such a large gap. Plus it might have been too brittle and cracked itself.
In my opinion, this failure mode is inexcusable. It would cost nothing to re-layout the printed circuit boards such that the resistors could be mounted against the board to prevent movement. It is obvious that having the mass of the big ceramic resistors supported by nothing but printed-circuit board foil won't work for long in the bouncing, swaying environment of an RV.
If you have a Vortex II vent fan, I recommend that you remove the printed circuit board and apply some type of support to the resistors to prevent future failures. You will have to remove the fan speed switch by loosening the set-screw on the knob, removing the knob, then the nut behind it. Then the circuit board with the resistors and selector switch should come out.
The problem is that the big, heavy ceramic resistors are just soldered to the circuit board with no support.
Luckily, I am in the aviation electronics business, so it was no problem to repair the broken solder joint on the resistor, but I also realized that preventing future failures was a simple matter of under-filling the resistors. Components in aviation electronics are usually under-filled with epoxy to provide structural support to improve reliability. Wherever you can eliminate movement between components, you eliminate the possibility of stress fracturing.
To help prevent future failures in my fan, I under-filled the resistors with silicone caulk. This should prevent movement that will lead to cracking. Epoxy might have been a better choice, but would have been much more difficult to install into such a large gap. Plus it might have been too brittle and cracked itself.
In my opinion, this failure mode is inexcusable. It would cost nothing to re-layout the printed circuit boards such that the resistors could be mounted against the board to prevent movement. It is obvious that having the mass of the big ceramic resistors supported by nothing but printed-circuit board foil won't work for long in the bouncing, swaying environment of an RV.
If you have a Vortex II vent fan, I recommend that you remove the printed circuit board and apply some type of support to the resistors to prevent future failures. You will have to remove the fan speed switch by loosening the set-screw on the knob, removing the knob, then the nut behind it. Then the circuit board with the resistors and selector switch should come out.
DD716TED wrote:Lynnmor wrote:
You could have added a PWM to the single speed fan and had variable speed forward and reverse. The cost would have been about $10. The resistors in the new switch waste power.
Where did you find a source for a PWM for $10.. Thanks
eBay, tons of them. I first tryed one that had a reversing already attached, but that one set up harmonics. If you get the really cheap one and a DPDT switch you should be good.
Lynnmor wrote:
You could have added a PWM to the single speed fan and had variable speed forward and reverse. The cost would have been about $10. The resistors in the new switch waste power.
Where did you find a source for a PWM for $10.. Thanks
You could have added a PWM to the single speed fan and had variable speed forward and reverse. The cost would have been about $10. The resistors in the new switch waste power.
