Testing The Ford EEC Power Relay (Brown Relay)

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.
   • 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.
   • Avoid probing the front of the EEC Power Relay connector to avoid damaging the female terminal with the test light's metal probe.
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 the following:

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.

Whenever you're ready, here are two EEC Power Relays I personally recommend —from brands I've used in the field and had solid results with over the years:

• Standard Motor Products RY-71T PCM Relay (Amazon affiliate link)
• Standard Motor Products RY71 Relay (Amazon affiliate link)

Buying through these links helps support this site and keeps these free tutorials coming —at no extra cost to you. It's a small way to say thanks, and I truly appreciate it.

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

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 working again. To troubleshoot the wiring between the EEC relay and its Ground point, see this guide —it's based on the F-Series but applies to most other models with this relay setup:

• EEC Power Relay To PCM Circuit Tests (1985-1991 4.9L, 5.0L, 5.8L Ford F-Series Pickup).

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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Sharing your diagnostic and repair experience not only improves this article, but also helps anyone else with the same symptoms or problems.