My fan has started to make a high pitch whine.  A gentle (!) tap on the side of the fan usually cured it for the rest of the ride, but now it keep coming back every time the fan goes on.  I am about to order a new fan, but I wanted to know if this was a frequent problem and if there was an easy fix.

Thanks

Some temporary solutions but the motor bearings are probably shot. Here is possible interim solution

http://advrider.com/index.php?threads/quick-fix-fan-dry-bearing-squeal.1037356/

And a permanent fix which is what I did for my 2010 GG and it has worked great so far.

http://www.trialsnuts.com/GG_Fan_Motor.htm

This is an example of the quick fix:

Drill a small hole in the fan housing than drill another hole in alignment on the fan structure (be careful that you don't drill so far through to damage the motor shaft)

warm up your motor till the fan comes on then shut down. Insert the red straw from a lubricant spray can and with the tube try and feel for the fan motor shaft  - I would reccomend a dry type of lube and sparingly spray lube onto the shaft then restart the motor and let the let the fan come on to help blow the lube back on the shaft hopefully getting into the bushing.

not a for sure cure but may help in the short run.

be careful not to over do it and flood the fan motor with the wet oil otherwise you could damage it

This motors come from mabuchi. Just buy another and replace.

1 minute ago, cascao said:

This motors come from mabuchi. Just buy another and replace.

Thanks.  Do you have a link to the actual motor?  

Try looking for c2162-60006

https://www.ebay.com/itm/DC-motor-HP-Carriage-Motor-Assy-C2162-60006-DD5O5830/231203808665?hash=item35d4d22599:g:fJQAAOxycD9TSvMu