Multi meter? That's not a ohm checker?
Have a look at this:
https://learn.sparkfun.com/tutorials/how-to-use-a-multimeter
How ever, you may be able to accomplish the same thing by putting your deck with coil attached in your ohm checker and wiggling the coil and screws whilst watching the meter. Eventually you`ll touch it just right, and the meter, either the ohm checker or a MM will bounce, or fluctuate so that you know you have found the spot of bad connectivity. With the multi meter you could just go from connection to connection and find where the drop off occurs, If the deck and coil check out and you cant find anything amiss with them you would want to start checking out the 510 at the mod to make sure its grounding good, but that would require a MM.