The Stovebolt Site Forums The Shop Area The Electrical Bay Basic relay diagnosis and test.

rasman,

To my knowledge, most automotive relays would have four 'prongs'.

I am wondering if your three terminal relay is actually a horn relay. The power would be applied to either of the terminals that had no continuity with each other or the case. When the terminal with continuity to the case was momentarily connected to battery ground, the relay would close.

There are three terminals.

Terminal 1 and 2 are the normally open contacts.

Terminal 3 is the ground for the coil (pull-in).

Power is supplied to the coil from a internal jumper from terminal 1 or 2. You can't see it as it's inside. Power must be present on the terminal that is internally jumpered...the other becomes energized when the relay closes.

If you apply power to one of the terminals NOT common with the case and touch the terminal that is common with the case to battery ground the relay should click. If it doesn't, try applying power to the other terminal NOT common with the case.

If the whole things blows up, blame your neighbor. Good luck.

Stuart