- Introduction
- The Most Common Cause
- Other common reasons
- Conclusion
Introduction
I recently had a customer call me after purchasing an RV equipped with a complete Victron Energy system. They were frustrated because every time they plugged the RV into a standard 15-amp household outlet, they heard a constant "click...click...click" coming from the inverter/charger.
Have you ever experienced the same thing with your RV, boat, cabin, or off-grid solar system?
If so, you're not alone. This is one of the most common troubleshooting questions I receive from customers.
The good news is that the problem usually isn't a faulty inverter. In most cases, your inverter/charger is doing exactly what it was designed to do, protect your electrical system. When the incoming AC power becomes overloaded, unstable, or falls outside the inverter's acceptable operating range, the transfer switch disconnects from shore power and switches back to battery power. Once the AC power appears stable again, it reconnects and tries again, resulting in the familiar "click...click...click" that many owners hear.
The Most Common Cause
One of the biggest mistakes people make is forgetting to change the AC Input Current Limit.
Imagine your inverter is programmed for a 30-amp RV pedestal because that's where it was last used. Now you arrive home and plug it into a standard 15-amp household outlet using an adapter.
As soon as the inverter begins charging the batteries, it may try to draw nearly 30 amps. The household circuit can only safely supply 15 amps, causing the voltage to sag.
The inverter detects the poor-quality AC power, disconnects from shore power, and switches back to battery operation. A few seconds later it checks the AC source again. If the voltage has recovered, it reconnects and starts charging once more.
If the overload still exists, the cycle repeats over and over. The clicking you hear is the internal transfer relay switching between shore power and inverter mode.
Many inverter/chargers let you limit the charging current.
If charging at 100 amps DC, the charger may require over 1,500 watts from the AC source.
On a small generator or household outlet, that's enough to overload it.
Fix:
- Reduce charger current
- Reduce AC input limit
Other common reasons
1. Weak generator
Small generators often cannot handle the initial charging surge.
The inverter accepts the AC...
...generator bogs down...
...voltage drops...
...transfer switch releases...
...generator recovers...
...cycle repeats.
2. Low AC voltage
A long extension cord or undersized wiring causes voltage drop.
Instead of seeing 120V, the inverter may only see 100–105V.
Many inverter/chargers reject AC below their programmed voltage window. With some inverters such as the Victron you can adjust this limit.
3. Frequency out of range
Older generators may produce unstable frequency.
Instead of 60 Hz they might swing between 56 and 64 Hz.
Many inverter/chargers disconnect when frequency moves outside acceptable limits.
4. Loose wiring
A loose neutral or loose hot conductor can make the inverter think shore power disappeared.
This is surprisingly common.
5. Bad pedestal or household outlet
A worn RV receptacle or loose household receptacle can intermittently lose contact.
6. Transfer relay failure
Less common.
After years of switching under heavy loads, the internal relay contacts may become pitted or worn.
7. Overloaded inverter output
Sometimes the inverter itself is overloaded.
It trips...
Recovers...
Tries again...
Looks like transfer switch chatter. I would try shutting off some loads or even all of them then see if that fixes it then start turning them on again one load at a time.
8. Incorrect inverter programming
Examples include:
- Wrong AC source type
- Wrong voltage range
- Wrong generator settings
- Wrong UPS mode
9. Sometimes the Easiest Fix Is a Reboot
I can't tell you how many service calls have been resolved with nothing more than a simple reboot. In fact, I believe I wrote an entire article on this topic because it solves more problems than most people realize.
Today's inverter/chargers are essentially sophisticated computers that monitor and control your entire power system. Just like your laptop or smartphone, they can occasionally experience software glitches or communication issues and simply need to be restarted.
Before you start replacing parts or assuming the inverter is faulty, try performing a reboot.
A soft reset can usually be done by turning the inverter/charger off and then switching off the main DC breaker that connects the batteries to the inverter. Leave the system powered down for a minute or two before restoring power and turning the inverter back on.
If the problem persists, a hard reset may be required. This involves safely disconnecting the positive battery cable from the system, waiting a few minutes, and then reconnecting it. This completely removes power from the inverter, allowing it to fully restart.
Always follow the manufacturer's recommended shutdown and startup procedures and use proper safety precautions when working around batteries and DC electrical systems.
It may sound too simple, but you'd be surprised how often a reboot restores normal operation and gets the system running properly again.
Conclusion
In my experience, nearly 80% of transfer-switch cycling problems are caused by an inverter trying to draw more power than the AC source can safely provide. A simple settings adjustment often solves the problem in minutes.
Understanding how your inverter charger manages shore power is one of the easiest ways to prevent nuisance shutdowns, protect your batteries, and keep your off-grid power system running reliably.
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