Colin answer is not correct as "heat" does not affect CQ (Copy Quality) it affect adhesion of the toner to the paper.
If you are TXing and Copies are faint at the edges than its a scanner issue, most likely needs to be cleaned. Open the area where you load your documents to fax out and clean the glass area with a cotton towel with windex on it. Might need to do several times to get the CW back up to normal.
Joe
December 2007