Testing The Ford EEC Power Relay (Brown Relay)

TEST 2: Checking For Power (High Current Circuit)

In this test step, we're gonna' check that the wire that supplies power (10 to 12 Volts DC) to the EEC Power Relay's high current circuit is actually providing this juice.

The wire that provides this juice is the wire labeled with the number 4.

As before, in TEST 1, you can check for this voltage with the EEC Power Relay connected to its connector or not.

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

1. Place your multimeter in Volts DC mode.
2. With the red multimeter test lead, probe the wire labeled with the number 4.
   • This is where a wire piercing probe comes in handy (to see what this tool looks like, click here: Wire Piercing Probe).
   • NOTE: Avoid probing the front of the EEC Power Relay connector with the multimeter lead (yes, I know, it's the easiest way to go about checking this circuit), but the metal female terminal could get damaged and this is a nightmare you don't need or want.
3. Ground the black multimeter test lead directly on the battery negative (-) terminal or on a clean metal spot on the engine.
4. Your multimeter should register one of two things:
   • Battery voltage (10 to 12 Volts DC).
   • Or no voltage at all.
   NOTE: Voltage should be present at all times (whether the Key is On or not).

OK, let's interpret your test results:

CASE 1: Your multimeter showed battery power. This is the normal and expected test result.

We now know that the high current circuit of the EEC Power Relay is being fed power.

The next step is to check/confirm that the EEC Power Relay is sending voltage out from the wire labeled with the number 3. Go to: TEST 3: Testing The EEC Power Relay Voltage Output.

CASE 2: Your multimeter DID NOT show battery power. Recheck all of your multimeter connections and repeat the test one more time

If the multimeter still does not register battery voltage (10 to 12 Volts DC) this second or third time around, then you need to find out why this voltage is missing.

These 10 to 12 Volts are provided by an inline fusible link (on the starter motor solenoid) or by a mega fuse on the engine compartment fuse box.

The most common cause of this missing voltage will be that the inline fusible link or the mega fuse is blown.

TEST 3: Testing The EEC Power Relay Voltage Output

In this test section, you're gonna' check that the EEC Power Relay is outputting the voltage it gets from the wire labeled with the number 4.

The EEC Power Relay outputs this voltage thru' the wire labeled with the number 3.

NOTE: This test step requires that you test wire number 3 with the EEC Power Relay connected to its connector.

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

1. With the EEC Power Relay connected to its connector.
2. Set the multimeter to Volts DC mode:
   • Probe the wire labeled with the number 3 with the red multimeter test lead and an appropriate tool like a wire piercing probe (to see what this tool looks like, go here: Wire Piercing Probe).
   • Ground the black multimeter test lead to a good Ground point on the engine or directly on the battery negative (-) terminal.
3. Turn the Key to its On position.
4. Your multimeter should read 10 to 12 Volts.

OK, let's interpret your test results:

CASE 1: 10 to 12 Volts registered on your multimeter. This tells you that the EEC Power Relay is OK and doing its job.

This test result also indirectly tells you that the wire labeled with the number 1 is providing a good Ground for the EEC Power Relay (and thus you don't need to perform TEST 4).

So, to make the long story short, the EEC Power Relay is NOT the cause of your Ford's no-start problem.

CASE 2: 10 to 12 Volts DID NOT register on your multimeter. Make sure that you're testing the correct wire.

If you still don't get any voltage to register on your multimeter, then the next step is to check that the EEC Power Relay is getting a good Ground on the wire labeled with the number 1.

If after confirming that the EEC Power Relay is NOT getting Ground on wire 1, THEN we can condemn the EEC Power Relay as bad. For this test, go to: TEST 4: Checking The EEC Relay's Ground Circuit.

TEST 4: Checking The EEC Relay's Ground Circuit

As soon as the EEC Power Relay gets power (on circuit 2), the relay activates.

The EEC Power Relay activates because its low current circuit is Grounded 24/7 (all of the time) by wire 1.

In this test section, we're gonna' test circuit 1 but there are some very important precautions you have to take:

1. Never apply 12 Volts to this circuit (either intentionally or accidentally), or you'll fry the connector or the wiring.
2. Never jumper circuit numbers 1 and 2 together, or you'll blow the inline fusible link (this bad boy is located at the starter motor solenoid).

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

1. Disconnect the EEC Power Relay from its connector.
2. Connect your 12 Volt test light's alligator clip to the battery's positive (+) terminal.
3. With the metal probe point of the test light, probe the wire identified with the number 1.
   • What I recommend you do is to probe behind the EEC Power Relay connector or...
   • Probe the wire itself.
   • Avoid probing the front of the EEC Power Relay connector to avoid damaging the female terminal.
4. The 12 Volt test light should immediately come On and stay On the whole time you're probing wire 1.

OK, let's interpret your test results:

CASE 1: The 12 Volt test light came On. This is the normal and expected test result and it confirms that the low current circuit is getting Ground.

So far, if you started testing from the beginning, you have checked and confirmed that:

1. The EEC Power Relay's low current circuit (wire 2) is getting power (TEST 1).
2. The EEC Power Relay's high current circuit (wire 4) is getting power (TEST 2).
3. The EEC Power Relay IS NOT outputting voltage (wire 3) (TEST 3).
4. In this test, (TEST 4), you have confirmed that the wire labeled with the number 1 is providing Ground for the low current circuit of the EEC Power Relay.

Taking all of your test results into account and having confirmed (in this test step) that the EEC Power Relay does have a good Ground, then you now know that the EEC Power Relay is bad.

CASE 2: The 12 Volt test light DID NOT come On. Make sure that you're probing the correct wire and repeat the test one more time.

If your 12 Volt automotive test light still does not come On, this tells you that this wire has an 'open-circuit' problem.

In layman's terms, this means that the wire is cut somewhere between it and Ground. What I suggest you do, is to Ground this wire using a jumper cable (or wire) and repeat the test (with the jumper wire providing a Ground, you should be able to repeat TEST 3 and pass it successfully).

Repairing this missing Ground will get the EEC Power Relay back to work.

Ford EEC Relay Test Summary

Well, you've come to the end of the article. It's my sincere hope the info helped and you were able to either eliminate the EEC Power Relay as bad or that you were able to condemn it as bad!

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