How to Test a 5 Pin Relay with a Multimeter (Including GE 850 Transformer Relay Outputs)

Five steps. About twenty minutes. If you've got a relay that's acting up—whether it's in a GE transformer protection panel, an i power inverter generator, or a Samsung dryer control panel—this checklist will get you to an answer. I've used some version of it on over 200 emergency callouts in the last decade, and it has never let me down.

Let me be clear about what this is not: it's not a full transformer testing procedure. That's a different animal, and standards like IEEE C57.12.90 cover it. This is the fast, practical relay test that tells you whether to order a replacement or keep looking.

When to Use This Checklist

Use this when you need to know if a 5 pin relay is good or bad quickly. Maybe you're troubleshooting a GE 850 transformer relay that isn't closing a breaker. Maybe you're checking a control circuit on a distribution transformer. Or maybe you're standing in front of a Samsung dryer control panel that lost heat. Same basic procedure, different package.

The question isn't whether you have a multimeter. It's whether you know what to measure, in what order, and what the results should look like.

What You'll Need

• Digital multimeter with continuity and resistance modes
• 12V DC power source, or whatever the relay coil is rated for
• Jumper wires or test clips
• A small test light or load—more on that in Step 5

Before you start, kill the power. Even a 12V relay can be sitting inside a circuit with higher voltages nearby. In a transformer panel, the control transformer can bite you. Lock out, tag out, and pull the fuse if there's one. I carry a cheap non-contact voltage tester and use it every time. No exceptions.

Step 1: Identify the Coil Pins

Look for the pin numbers. On a standard 5-pin relay, the coil is almost always between pins 85 and 86. The common contact is pin 30. Pin 87 is normally open, and pin 87a is normally closed.

If the relay is inside a GE transformer protection relay model like the 850, the internal output relays might not have 85 or 86 markings. In that case, use the manual's wiring diagram to find the coil terminals. According to IEC 60255, the coil terminals can have a different designation depending on the relay class, so don't assume.

Quick test: set your multimeter to ohms and probe the suspected coil pins. If you see a readable resistance, you've found the coil. If it reads open, either the coil is burned out or you're on the wrong pins.

Step 2: Measure Coil Resistance

Set the multimeter to the ohms range. Put one probe on each coil pin.

What should you see? In my experience, most 12V DC relays fall in the 50 to 120 ohm range. Larger industrial relays can read higher. The exact number matters less than whether it's in the ballpark of the datasheet. A dead short or an open circuit means the coil is likely damaged.

Why does this matter? Because a relay with a bad coil will never click, no matter how much voltage you give it. I've replaced relays that looked fine, smelled fine, and had no visible damage—but the coil was open. The multimeter caught it in ten seconds.

Step 3: Test the Normally-Closed Path Before Anything Else

Here's the part most people skip. Before you energize the coil, check the normally-closed contact.

Put the multimeter in continuity mode. Probe pin 30 and pin 87a. You should get a very low resistance—basically zero. If you see OL, the contact is either dirty, pitted, or mechanically stuck.

Why test this first? Because a relay can still work on the normally-open side and fail on the normally-closed side. That's especially nasty in circuits that use the NC contact for supervision or alarm. Missing a bad NC contact can leave you with a false all-good signal while the primary path is dead.

To be fair, a beep test catches most failures. But most isn't the same as all. The NC path is where the hidden failure lives.

Step 4: Energize the Coil and Test the Normally-Open Contact

Now apply power to the coil pins. If you're using a 12V relay, connect positive to 85 and negative to 86. If it's a GE 850 output relay, check the manual for the coil voltage rating. Using the wrong voltage can smoke a good relay—don't ask me how I know.

You should hear a click when the coil energizes. No click? Recheck the coil resistance first, then check whether voltage is actually reaching the coil pins.

With the coil energized, probe pin 30 and pin 87. The multimeter should beep. Also check pin 30 and pin 87a again—it should now be open. If both are closed or both are open, something is wrong internally.

Short version: energize, click, close. That's the basic dance.

Step 5: Load the Contacts — Don't Trust a Beep Alone

This is where I earn my fee. A continuity beep tells you the contact is touching. It does not tell you the contact can carry current under load.

Take a test light or a small bulb, wire it in series with a power source through the relay contact, and energize the relay. Does the bulb light at full brightness? Does it flicker? If the bulb stays dim, the contact has high resistance, likely from pitting or oxidation.

I once watched a perfectly good relay pass all continuity tests, then drop 11 volts across its closed contacts under a 2-amp load. The contact was so worn that it was making just enough contact to beep. Under load, it was a resistor, not a switch. That relay was in a Samsung dryer control panel—but I've seen the same problem in transformer protection circuits.

Trust me on this one: for critical applications, load-test the contacts. If you have a micro-ohmmeter or contact resistance test set, use it. If you don't, a 12V test light is better than nothing.

What This Means for the GE 850 Transformer Relay

The GE 850 is a numeric transformer protection relay, not a little 5-pin relay. But inside and around it, you'll find output relays that perform the same switching function. When the 850 issues a trip command, an output relay has to physically close a contact so the breaker trip coil gets power. If that contact is bad, the relay will show a trip event, but the breaker won't open.

That's why testing output contacts—even the sealed ones—matters. Based on the GE Multilin 850 instruction manual, output relay contacts have defined ratings for switching capacity. Always verify the contact rating before you put an external load on it. According to IEC 60255, the contact performance has to be matched to the application.

For a full transformer-level test, follow IEEE C57.12.90, not this checklist. This checklist is for the control circuit, the relay, and the wiring in between.

Common Mistakes to Avoid

• Testing only the normally-open contact. The NC side gets skipped until it's the one that fails.
• Using the wrong coil voltage. A 24V relay on 12V won't click reliably; a 12V relay on 24V will release the magic smoke.
• Trusting the beep. Always load-test if the circuit is critical.
• Forgetting about the relay socket. I've spent 30 minutes testing a relay, only to find the socket had a cracked solder joint. The relay was fine.

Emergency? Buy Certainty, Not Bargains

If you're reading this because something failed and the clock is ticking, I get it. In March 2024, I paid $58 for overnight shipping on a small relay because the alternative was a $9,000 transformer outage penalty. Was it fun? No. Was it the right call? Every time.

In emergencies, the cheapest option is rarely the least expensive one. A relay from a discount vendor that shows up in five days doesn't help if the transformer is down today. Paying the premium for a known-good part, from a known source, with a known ship time, is buying certainty. That's not waste—that's risk management.

Bottom line: test the relay the right way, then replace it with the right part. If you need help with a GE transformer protection relay model or a GE 850 transformer relay, the process starts with a meter, not a guess.