Bathroom exhaust fan replacement/repair

Hi all,
My bathroom fan is about 30 yo Nutone Model 8831 FWIW. It does not move a lot of air, as it's rated 76 CFM, but adequate, since it's 1/2 bath w/o a tub.
The falp valve spring has rusted out and it no longer closes, which in a winter caues a draft. The fan is mounted in wall. I would try to fashion a spring for it, if I could remove the fan, but it seems that I would have rip the wall apart (it's drywall).
Hate to thrash a working fan for a tiny spring, but there's no way to do anything with the fan in place.
Anyone been successful with a similar project?
Rich
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
egads, yes.....just went round n round over replacing a ceiling fan. It too was a NuTone 8 yrs old. The fan motor totally died. This story is tooo long to tell. But, can tell you this....Seattle Lighting could get another but 3 week wait and 100 dollars, Home Depot could do the same ...3 week wait 150 dollars. Got it at Platt Electric for $70. Had to buy the entire unit but all I had to do was unplug the bad fan with motor and put the grid back on. If I watch enough HGTV maybe could do something artistic with that new housing. LOL
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

The motor is easy :-) HD has some generic motors for these fans.

Hope I do not have to get artistic over a small spring. Been thinking about driving a couple of screws into the damper (flap) to serve as a counterblance, but this thing can flip too far and not comeback. Maybe put in something that will prevent it from flipping too far and use the counterbalance.
Since the old spring disintegrated completely, I don't even know how it was installed. It has to a very light spring, otherwise this thing will not open.
Rich
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.