I have a 2008 MDX, I have a noise in the dash I believe caused by electrical relays making a crackling noise. The noise continues even if the car is not running but the key is turned on. Any ideas?

 

Try checking anti-freeze level. See if it's topped-off. I have same problem on 2003 Mdx. Possible air pockets in heater core system. Turn on heat to circulate fluid. Make sure to top off when engine is cold. Then if it continues try flushing it.

 

No that is not it, you can feel the green relays clicking

 

Sorry if I am reposting what smashn.kev posted but I can't get those links to work. I would suggest pulling the fuse for the HFL and seeing if that might be it. The HFL units have been known to cause a parasitic draw on the batteries on the TL. You don't mention whether or not you are having any issues with your battery or not. We had an 07 MDX and didn't exhibit the symptom you mention but did have it fail completely on us.
I guess my point is that HFL is active with the key on.
Also sounds like you may have narrowed it down to the "green relays." Have you identified what these are via your owners manual and/or are they marked on the fuse box cover??