How To Bench Test A Ford Relay (Large Relay)

Testing The Relay

Since your Ford vehicle uses quite a few of the exact same type of relay, you can swap them out and in this way test them. But if you're like me, sometimes you need a real test to make absolute sure that the relay is bad.

Well, you've come to the right place for such a test.

You'll need three very important things:

• A multimeter (analog or digital).
• Two jumper wires with alligator clips on the ends.
• Maybe a helper.

OK, to get this test going, this is what you'll need to do:

1. Place the relay you need to test close to the vehicle's battery (you'll need battery power and Ground for this test).
2. Using a jumper wire with alligator clips, connect terminal 85 of the relay to the battery's Ground (-) terminal
   • The photos in the image viewer are an exact representation of what goes where.
   • If you don't have such a jumper wire (with alligator clips), you can run down to your local Radio Shack (even Wal-Mart) and buy some and make your own jumper wire.
3. Activate the relay by connecting male spade terminal 86 to the battery's positive (+) terminal.
   • It's normal to hear a small clicking from the relay when this connection is made.

4. With your multimeter in Ohms mode: touch terminals 30 and 87 with the multimeter leads (as seen in the photo).
   • It doesn't matter which color lead goes where, since the polarity does not matter for this test.
   • You may need a helper for this operation, unless your multimeter leads have alligator clips on the end of the leads.
5. Once the last connection is made, your multimeter should show continuity. If it doesn't show continuity, recheck all your connections and retest.
6. Remove and reconnect the jumper wire to terminal 86 several times, as you eye-ball the multimeter.
   • When the jumper wire IS NOT connected to power, the multimeter should show NO CONTINUITY.
   • When the jumper wire is connected to power, the multimeter should show continuity.

OK, let's interpret your test results:

CASE 1: Your multimeter showed continuity. This tells you that the relay is OK and not the cause of the problem.

CASE 2: Your multimeter DID NOT show continuity. This tells you that the relay is bad and needs to be replaced.