Generac generators are powerful machines that are sure to give you excellent performance. They are designed to deliver high power, reliability, and durability.
However, like anything mechanical, they also have issues.
Error 2780, “charger missing AC,” is one of the most common errors with these generators. In most cases, the user will panic when they see it.
But it’s mostly nothing to worry about. It could mean a false error, which should be easy to handle.
Keep reading this guide if you still don’t know what it means. We will explain the error and solutions.
Charger Missing AC Error Indicators
The missing charger error is indicated when it happens. You may wonder why you have a red or yellow light on the side of your Generac generator.
A yellow light indicates the missing charger error. Everything else might be working, but the light won’t go away because the computer in your generator is still noting that particular problem.
Green and yellow lights could still mean the same thing. So, even if you don’t see the exact missing AC message, understand something is wrong, and you need to deal with it as soon as possible.
The Significance
The light means that there is not enough power going into the battery charger of your generator.
As you may already know, the battery powers everything in your generator, and you must ensure it has enough power.
Under optimum working conditions, the built-in battery charger needs 120 volts to operate.
So, if an issue can’t get this power or comes in too low, you are bound to encounter such issues. Knowing what you are dealing with is vital before attempting any repair process.
How Does The Transfer Mechanism On The Generac Work?
To understand how the missing AC error happens, we need to discuss the basics of the switch. Here we have the transfer switch, which may have other names according to individuals.
When you search the internet on the power transfer mechanism in a Generac generator, you will come across the terms T1 and T2 in many descriptions.
Simply put, these are the load terminals of the ATS.
They are connected to the N1 and N2 terminals to transfer energy from the generator to the load, especially in a 240/120V single-phase system.
The transfer switch transfers electrical load from a utility or normal power source to the generator or standby power.
When a power source fails or a substantial reduction happens, the transfer of electrical energy happens automatically.
A disconnect circuit breaker fuses within the transfer switch that disconnects power transfer.
Imagine what happens if the switch/circuit breaker stops working effectively. That is when the electrical energy to the load is not enough.
That is where we get the charger missing error.
What Causes A “Missing AC” Error?
As stated above, the error means insufficient power is getting into the battery charger system.
Missing AC is simply saying there is a connection issue – the transfer mechanism above is not working, and you need to check it.
Here are the possible causes:
False Alarm Due To Power Outage
You are bound to meet this error sometime during your operation with the Generac generator.
No matter the model or age, prepare to deal with it because of the possible power outages experienced.
Every time the generator experiences a power failure, it will bring on the “missing AC” error. And the error will remain on until the generator starts and transfers enough power.
So, when there is a power outage, the generator will treat it as an error. The controller detects when there is not enough power to the charger.
However, you can treat this as a false alarm because you know what is happening. Although, it’s not advisable to treat all such errors are false and ignore them.
Sometimes even a power outage can lead to a more serious issue in the long run, which might require troubleshooting.
T1 Connection Problems
T1 is the connection to the load from the side of the transfer switch. It acts as a circuit breaker to protect the system against power outages.
It’s normal to do its job during the time described above.
A “charger missing AC” alarm comes on when the power from the T1 wire is not delivering the 120Vs to the generator.
Now, understand that there is a power loss to the charger input from the time it takes for the engine to start, run and transfer. Such a reading is not false.
This error could be due to a wiring problem that might have happened during installation. It could also be due to a blown T1 fuse in the transfer switch.
Since the work of a fuse is to break the circuit when there seems to be an abnormal power input, it does its job when the issue does occur, cutting any connection between the battery and the load.
Consider this; as long as the controller is powered up from the battery and there is no charger input from T1, the battery will die after a short period.
In the end, your generator will stop working altogether for the lack of enough voltage.
Such things might damage your battery, forcing you to buy a new one. It would therefore be good to disconnect it while figuring out the issue.
Dealing with the fuse is much easier than investing in a new battery.
How To Resolve A Generac Charger Missing AC?
If the charger AC missing error came on after an outage, you need to clear it by first checking the connection. Here are a few ways of handling it:
Check The T1
The T1 performs only one function on the Generac generator – connecting the harness under the controller. It is a 2-wire harness that quickly connects the plug on one end.
You should easily notice it because it’s the only wire out of the controller as a real wire. Others may come out as plug connectors, which should not be your concern now.
This wire will also be covered by a heat-shielding fiberglass sleeve, making it even easier to identify. Check if it’s broken or disconnected, and then reconnect it.
That should take care of the missing AC error.
Check The Circuit Breaker
Is the generator running but not providing power to your home? Check the circuit breaker.
It is still the T1. Only this time, the generator is not off.
Also check:
The factory side on the block for any unstripped wires connected to hot or neutral. Look for blacked-out terminals on either side of the plug-in connectors.
Continuity between the neutral and the main neutral plug. You can identify this part from the Genset.
For poor terminal contact inside the bulkhead connector. It could require a schematic and more advanced solutions like back-probing.
Whatever you do, any Generac charger missing AC error should not be ignored. You can verify if it’s serious by disconnecting the battery cable to see if the controller turns off.
Checking the circuit breaker is only effective if the generator runs during an outage but not powering the load.
The break could be located behind the cover on the side enclosure or under the main lid on the control board.
Make A Service Call
If the generator is not running and the DTE power is on for the load, you need to call in an expert. Except you are an expert, do not attempt fixing it yourself.
Conclusion
You might use your Generac generator for a long time without experiencing the charger missing AC error. That should be great, but it does not mean you won’t face it someday.
Having some knowledge of it will come in handy to resolve when the time comes.
And if you have faced the error, we hope this guide has been helpful. Also, you can find the information in your user manual if you are wondering what else is there.
