I generally just replace them, especially when the fan in question is the more inexpensive type.

I'm a bit confused by the "opening the ceiling' wording. An entire unit can usually be replaced by simply removing the old and installing the new---unless the exhaust piping has to be attached in the attic.

Generally, you purchase the whole fan, "like", assembly, and then you can quite easily remove the motor/impeller assembly from the existing housing, remove the impeller retaining clip (if it has one) remove the impeller from the defunct motor, place it on the new motor and reinstall into the housing and insert the balance of the remainder into the trash can.

Ok, thanks guys.

Handymac, if there's no access from above, I don't know how you change the housing without added work and cost. In these cases I just find (hopefully) the same model and dimensions, then swap out the inner plate with impeller. Otherwise, I assume some ceiling repair, repainting, etc., but try not to do that.

Snoonyb, that's about what I do, except that if go to the trouble to find the match, I install the inner assembly into the existing housing, plug it in, and be done with it.

" except that if go to the trouble to find the match, I install the inner assembly into the existing housing, plug it in, and be done with it."

Thats all well and good, except that as often as not the new impeller can be different in dia causing a loss of efficiency.

First of all, your wasting your time to look for parts in H.D., Lowes or any other big box home supply store.

Get the model number off your existing unit and to to a commercial appliance parts store and get the correct parts.

"Get the model number off your existing unit and to to a commercial appliance parts store and get the correct parts."

And pay more than a whole new unit (especially if you are paying a pro to do the work, he gets paid the same rate to drive around as to install things).

I start with model# and dimensions.

Might as well buy the whole unit from HD (if it's there) and harvest what you need. But for some of the old, small 50 cfm Nutones, I know of one old-fashioned hardware store that keeps two motor housings in stock. Occasionally, one of our HD's has ONE motor assembly on the shelf but it's such a cr@p shoot to even make the trip.

As for the appliance parts store route, that might be an idea from the perspective of time-saving. I will check if they (Tribles) actually keep any motor housings onhand. (probably not, but we'll see.)

sometimes you can find parts online for good prices. Of course, you then need to wait for it to arrive.

It's possible to get replacement bare motors sometimes. Broan are good about having replacement bases -fan/motor, that fit into the existing box. They have a plug/socket, so you don't have to do any wiring.

That being said, I just replaced one, and it turned into quite a big job because the replacement base was more than a whole new unit.

I put in a new one, which meant a bit of carpentry etc because the boxes were different sizes.

I had to cut the nails/screws holding the old one in, and insert the new box from below, which required a bigger hole, and careful saw cuts in addition to allow for the nailing tabs. The fan cover covers the repairs from it, in the ceiling.

The insulation around the duct had no vapour/air barrier so I used a mylar bubblewrap product and foil tape for it. Since the house was old enough to not have had an vapour bag around it, I built one with the mylar stuff and sprayfoamed it in. Lastly I decided the fan should have its own switch, so I could use one of those timer/humidity sensing ones.

It turned out well and I'm glad I did it, it works better and is much quieter.

But in most cases, just replace the fan motor and base.

I seem to recall ordering a motor from Broan or NuTone and it not being horribly expensive. Of course, for the really cheap ones, it might be easier to scavenge parts from a new one.