To layout my situation, I have a 12V DC pump with a built in float switch that I don't want to try to crack open and possibly compromise the waterproof of. The pump draws around 6-7 amps. I would like for an alarm to sound when the pump is running, and was thinking of trying to use a relay to trigger this. However, from what I can tell most relays have very high resistance coils that likely aren't meant to be run in series with another load and I believe will limit the current to the pump too much. Is there any kind of low coil resistance relay that is made for a purpose like this?
Alternatively I was looking at trying to use an inline current sensor to trigger activate a relay but don't have any experience w/ those and aren't quite sure they would work correctly. I was hoping I could find some kind of current sensor / relay combination but haven't have any luck so far.
Otherwise, any other ideas on how I could do this?