According to this, the resistance should be 4.5 ohms. As MenaceFire said, if it measure much lower than that, replace it. And you do need a plunger.:
The schematic is available at ipdb.org - maybe this snippet will help you. If you know where it was mounted, you should be able to see where the two loose wires were connected - they're not too long - you won't have many options. The replay unit must be somewhere close by.