Commercial bunn brewer is making loud buzzing sound

Bunn switches if the rocker style as the looks like will have two leaves on the side of the switch that will need to be squeezed in order to get it past the square hole. These can be really tight but if your sure it's at fault then just crush it to remove the pieces. The new on should snap in if the hole was not damaged.
* Since your checking the brewer you should get the manual that may be available from Bunn.com (I haven't checked for this model but they usually post the manuals)
* This seems to be a home version of a VPR commercial brewer (but nicer). So expect the same parts for the fuse, thermal fuse, thermal disk (or thermostat).
* Note: If your not familiar with Bunn brewers then make sure you look at every piece of wire as some high limit fuses are inside plastic tubing or heater braiding.
* Thermal disks look like a metal button with a ceramic cap or button attached to it. This can be a high limit (reset-able) or a thermostat. * It may have a standard thermostat with bulb but it may be a thermsistor probe with a PC board to control the brew heat.
* Final; this is the 3d question on this particular brewer. All have similar problems with heating. It's the same with VPR's. If I set them up I know it works properly. It's when someone moves them to another office that's the problem as they dump out the water prior to the move then plug it in without refilling the tank. Thermal fuse blows. There is a link below showing how to set up this brewer.
Aloha, ukeboy57
https://www.bing.com/videos/search?q=bunn+grx-b&&view=detail&mid=E6D1ADD550DA3DA5B120E6D1ADD550DA3DA5B120&&FORM=VDRVRV

This is a common question for the BTX-B.
It's a commercial brewer that needs to be pre-filled prior to turning on.. It also needs to be filled again with a full carafe for it to brew properly. I have a link below that will explain how to set up and use this brewer.
Aloha, ukeboy57
https://www.bing.com/videos/search?q=bunn+grx-b&&view=detail&mid=E6D1ADD550DA3DA5B120E6D1ADD550DA3DA5B120&&FORM=VDRVRV

This is a common question for the BTX-B.
It's a commercial brewer that needs to be pre-filled prior to turning on.. It also needs to be filled again with a full carafe for it to brew properly. I have a link below that will explain how to set up and use this brewer.
Aloha, ukeboy57
https://www.bing.com/videos/search?q=bunn+grx-b&&view=detail&mid=E6D1ADD550DA3DA5B120E6D1ADD550DA3DA5B120&&FORM=VDRVRV

Sounds like the thermostat needs to be replaced adjusted or the probe to the thermostat is covered in scale, and it cannot read the temp correctly. Remove top panel and check probe, if fine no buildup, follow probe line to thermostat and set to a lower setting, if same problem replace thermostat.

BUNN G-3 IS A RETAIL COFFEE GRINDER and You are talking about a COFFEE BREWER Any way

It sounds like a bad thermostat and needs to be replaced.

What model of Bunn is this? If it is a bx-b or any of the other home models, what has happened is that the plastic pour-in tray has become brittle and cracked where it mounts onto the tank. The only repair for this is to replace the tray with one from another brewer (possibly your local bunn Dealer has an old brewer lying around). If it is a commercial brewer (VPR, VPS, Ect) there will be a sael leaking on the top of the tank.

You may have a thermostat problem.

Contact a Bunn service center and have the unit checked.

It is possible there is a problem with the tank heater. Please get the model and date code located on the bottom of the machine. Then contact customer service with this information. The brewer contains a 3 year warranty and if your brewer is 3 years or less will be replaced at no cost. If it is over 3 years, then it will be replaced at a reduced cost.

Have you tried to brew without coffee to see how long it takes? If yes then use a pair of channel locke to remove sprayhead and then use the deliming sprding that came with your bunn and clean the brew line then try again, if you still get the ame result, the brewer needs to be descaled.

There is no one diagram that will show you how to change all of the seals in your brewer. The manual for this brewer with the instructions to replace them can be found at this link: http://www.bunn.com/pdfs/commercial/manuals