The right rear speaker in the cargo compartment has a loud static noise with the radio on or off. Tried disconnecting and reconnecting the battery but diidn't change anything

 

Likely bad ground or speaker, IMO. Could also be a short somewhere.

 

What year is your Equinox and what engine does it have?

 

2005 3.5 litre engine

 

I'll assume that you have a 2005 Equinox which only came with a 3.4L. You could have a wiring issue somewhere, but the fault is most likely with the amplifier located under the rear seat on the passenger side. Unplug the harnesses from the amp and inspect them for damage or corrosion. If you don't see anything wrong, the amp is probably bad. The amp does fail a bit more often on the 2005 models compared to later years. Although, the 2006 Equinox is nearly identical to the 2005 model, they use different amplifiers that are not interchangeable.