My 1992 Honda accord has been sitting for a few months in my backyard. I recently got it out on the road when I turned it back on the heater was not turning on it was not blowing any air at all none of the buttons are lighting up either.
The D4 light is also blinking.
I replaced the blower motor relay and it is still not working. After doing so the turning signals stopped working as well. Anyone know what this could be?

 

I would initially diagnose these as individual problems that aren't related.

For the blower relay, try reinstalling the original relay to see if the turn signals start working. Do the hazard lights work?

For the blower, I'd unplug the electrical connetor to the blower motor and use a test light to see if your blower motor is getting 12V on one of the wires.

Since the D4 light is on, you have some transmission codes. You can see the writeup in the common diy thread on top of the gen tech help forum for how to checkf or codes.

 

Not sure where you live , you stated that car has been parked in your back yard for a few months , you might want to look for pack rats issues chewed up some wires ?