Where can I find the existing Model number? Do I have to remove the fan?

I found the model number on my Broan model 688 fan by removing the face bezel and looking on the face of the motor mount frame. Use a flash light, because, on mine, it was stamped in ink that had faded somewhat.

It is pretty standard. And yes you have to remove the fan. But it is easy. You should want to use the new fan it comes with. Make sure you vacuum out the housing of any dirt or lint before installing new motor. You can replace the whole thing in about an hour.

The model number might be located on the inside housing. You will have to remove the grille to see the inside of the housing. Please note that over time, a sticker with the model number could wear off. If you have questions and would like to speak with a customer service person, dial 800-558-1711. We will be happy to assist you. Thank you.