My Dacor raised vent RV36 (equipped with the CABP3 blower assembly) started malfunctioning. It was first installed in the house in 1999 but was seldom used until 2011, when we bought the house and moved in. The previous owners used to live far, far away and only came to this house once in a blue moon. The vent performed OK, though a little noisy, until now. The problem is with the blower motor. It stopped working on the high speed and was functioning noisily at lower speeds. I thought it may be a problem with the blower motor or capacitor and so took out the whole assembly, overhauled it and changed the three motor mounts as the old ones had gone sticky. I also checked the capacitor value using a Fluke multi-meter and it showed up as being 5 micro Farads - in other words, it was to spec.

Next, I connected the blower motor to the capacitor and to the 120 volts mains outlet directly (i.e., bypassing the RV36 assembly altogether). It ran like a charm, with no unusual noise of any sort - i.e., no problems with either the bearing or the windings. Smooth as silk.

However, when I installed the blower back into the RV36 and connected it to the logic board, it did not run properly. Here’s what happened:

At High speed setting – the motor hummed loudly and was taking about a minute to complete a single rotation. I got out of this hastily, as I felt it would burn out the windings.

At Medium speed setting – the motor ran, but it was noisy and slow. Gave me an uncomfortable feeling that the motor may burn out if I continued to run it at this setting for any length of time.

At Low speed setting – the blower ran at a high speed (much faster than it did earlier at this setting, but slower than at medium setting), but it was still a bit noisy. I am not comfortable about the noise and have a feeling something’s not quite right. I have a feeling the noise may be associated with the circuitry handling the speed control (thyristor drive ?).

The rest of the functions work OK, though I need to press the function buttons a little harder sometimes. The raised vent portion goes up and down smoothly (I had cleaned and re-lubricated the gear box) and the limit switches work as they should – no problem there.

I had a look at the circuit board and one of the components, immediately next to the glass fuse, looks like it is frosted over. Looks like a resistor to me (see attached photograph) But apart from that, it all seems to be OK. What could be wrong here and what else should I be checking out ?

I found this.......

https://www.electronicspoint.com...identifying-part.279128/