Need assistance with Wiring for Nest Learning Thermostat

[FinnleyDolfin]

I just bought a house and wanted to upgrade the Trane TCONT802AS32DAA. Outside is a Trane 4TTX6024E-60E. In the attic crawl space is the blower and gas furnace, model unknown. 

Here's how the existing thermostat is wired. 
Red wire - R, jumped to RC

Blue wire - Y2
Orange wire - W1 or W2
White wire - W2 or O
Yellow wire - Y
Green wire - G
Brown wire - B

The back of the thermostat is labeled Heat Pump or Heat/Cool. Anything after "or" is for the Heat/Cool configuration. 

I was told we have a heat pump but not 100% certain. 

After hooking it up to the Nest thermostat and trying to cool it just made the compressor clunk loudly over and over. I watched a few YouTube videos and didn't see anything which matched exactly to what I have, especially with the brown wire. 

So, how do I hook it up to get it working?

[zoeuvre]

Hi FinnleyDolfin, 

Thanks for posting here in the Community forum and for showing interest in our Nest Thermostats.

Are you located in North America or Europe? What type of Nest Thermostat do you have? And could you post a screenshot of your how you connected the wires to the Nest Thermostat so we can take a deeper look?

I'll look forward to your response. 

Best,

Zoe