I have a 2005 FEH (65k miles) and have been having a starting issue the past week or so (not starting with a/c running, not starting on first key turn) and last night it died completely (dim to no dash/dome lights, no horn on door lock, constant clicking of some relay even the morning after the car sitting there all night). I believe I have the original 12v battery and am getting a replacement today, and also considering replacing some m/e relays.

I will also schedule a dealership service soon, but am wondering if there are things I should specifically ask them to check,? What else tends to go wrong, especially those that seem tough for them to diagnose? Which are easy enough for a rookie to fix at home?

M/E Relays
Blend Door Actuator
ABS Tone Ring
330V battery fan
??


PS: my OEM battery was replaced and seems to have everything running fine now.

 

That's the thing with most new cars these days. Lots of weird things can happen if the battery isn't up to par. I'd guess you might not need any other work right now.