Okay, let's break down why you might be seeing an "Open Ground" indication on your GFCI tester even though you've verified continuity between the ground and neutral. This is a common troubleshooting scenario, and understanding the nuances is key.

Understanding the Tester and the Problem GFCI Tester Function

A GFCI tester primarily simulates a ground fault (a small current leak to ground). It does this by creating a deliberate, small current path from the hot wire to the ground wire. If the GFCI is working correctly, it should trip instantly (or within milliseconds) when it detects this imbalance between the current going out on the hot wire and returning on the neutral wire. The "Open Ground" indication means the tester isn't able to create that current path to ground.

Continuity vs. a Good Ground

Having continuity between neutral and ground is not the correct configuration and is dangerous. Ground and neutral should only be bonded at the main service panel. Bonding elsewhere can cause circulating ground currents, and nuisance tripping of GFCIs, and may be the cause of your problem.

The "Open Ground" Lie

In this case, your "Open Ground" indication doesn't necessarily mean the ground wire is completely disconnected. It could mean the resistance in the ground path is too high for the tester to function properly, or that current is flowing in your ground wire causing the tester to fail.

Possible Causes and Troubleshooting Steps

Here's a methodical approach to diagnosing the issue:1. Neutral-Ground Bond Location



Crucial

The only place the neutral and ground should be bonded together is at the

main service panel (where your power enters the house). Check for Accidental Bonding

Search for other locations where someone may have accidentally tied the neutral and ground together in a junction box, at another receptacle, or within a light fixture.

Testing

Turn off the breaker to the circuit in question. Disconnect the ground wire from the GFCI. Measure the resistance between the ground wire and the neutral wire at the GFCI location. This should be very high (ideally infinite). If you get a low resistance reading (close to zero), you have a neutral-ground bond somewhere other than the main panel.2.

Voltage Between Neutral and Ground

Using your multimeter, measure the AC voltage between the neutral wire and the ground wire at the GFCI receptacle. This should be very close to 0 volts. If you read more than a few volts, it indicates current flowing on the ground wire, which is a problem.3.

Loose Connections



Important

Turn off the breaker before doing any wiring work. Carefully inspect all wire connections within the GFCI box and in any junction boxes upstream (towards the main panel) on that circuit. Make sure the connections are tight and properly made. Look for loose wire nuts, screws that aren't tightened, or wires that are improperly inserted into push-in terminals.4.

Ground Wire Size and Quality

Is the ground wire the correct gauge (size) for the circuit? It should be the same size as the hot and neutral wires. If it's too small, it could create higher resistance. Check for corrosion or damage on the ground wire.5.

GFCI Receptacle Itself

Although less likely, the GFCI receptacle itself could be faulty. Try replacing the GFCI with a new one of good quality.6.

Shared Neutral Circuits (Multi-Wire Branch Circuits)

If you have a multi-wire branch circuit (where two hot wires share a common neutral), it's critical that the neutral connection is solid. A broken neutral in this configuration can cause dangerously high voltages on some outlets. It can also cause current to flow on the ground wire. This is complex and if you suspect this, consult an electrician.7.

Correct Wiring

Verify the the GFCI is wired correctly. The line and load side matter. Line side being the main service and load side going on down to the remaining devices on the circuit.

Important Safety Notes Always Turn Off the Breaker

Before working on any electrical wiring, turn off the circuit breaker that supplies power to the circuit you're working on. Verify the power is off with a non-contact voltage tester or multimeter.

If You're Not Comfortable

If you're not experienced with electrical work, please call a qualified electrician. Electricity can be dangerous, and mistakes can lead to shocks, fires, or damage to your home.*

Local Codes

Make sure all your electrical work complies with local electrical codes.

In Summary

The "Open Ground" indication, combined with the continuity between neutral and ground, strongly suggests a problem with how your grounding system is configured. Most likely, you have an unintentional neutral-ground bond somewhere other than the main service panel, or current is flowing on your ground wire due to some other issue. Carefully follow the troubleshooting steps above to identify the root cause. Flag for review