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RV Solar Works Sometimes But Not Always? Here’s What to Check

A common complaint I get is that an RV solar system seems to work perfectly sometimes, but other times it barely charges—or appears to stop charging completely.

That doesn’t automatically mean something has failed.

The important question is whether the solar system is reacting normally to changing conditions, or whether there is an intermittent problem somewhere in the system.

This article will help you tell the difference and narrow down where the problem may be.

If your main concern is poor solar performance specifically in shade or overcast conditions, see: Does Solar Work in Shade or Cloudy Weather?

Quick Check: Is the Solar Actually Failing?

Before troubleshooting anything, try to identify a pattern.

Pay attention to when the solar stops working.

Ask yourself:

  • Does it happen around the same time every day?
  • Does it happen when the battery is nearly full?
  • Does output return later without you doing anything?
  • Does it happen when certain RV appliances are running?
  • Does the controller still show panel voltage?
  • Does moving the RV or changing sunlight conditions affect it?
  • Does the system completely stop producing even in good direct sunlight?

Patterns are extremely useful when diagnosing an intermittent solar problem.

A system that changes output throughout the day may be behaving normally.

A system that randomly loses all solar input under otherwise identical conditions deserves a closer look.

Step 1: Check the Battery State of Charge

This is one of the easiest things to overlook.

A solar controller does not necessarily send maximum charging current to the battery whenever sunlight is available.

As the battery becomes charged, the controller reduces charging.

You might see:

  • High charging current earlier in the day
  • Much lower current later
  • Float mode
  • Very little apparent charging
  • Charging that seems to start and stop

That can be completely normal.

A Simple Test

Check the solar system when the battery actually needs charging.

If the battery is already nearly full, low solar charging current doesn’t tell you very much.

If possible, compare what the controller does with:

  • A partially discharged battery
  • Good direct sunlight
  • Minimal loads operating in the RV

If solar production increases significantly, the system may have been working normally all along.

Step 2: Check Whether RV Loads Are Hiding the Solar Output

This catches a lot of people.

Suppose the solar panels are producing 8 amps, but the RV is currently consuming 7 amps.

You may only see a small net increase at the battery.

Depending on how you’re monitoring the system, it can even look like the battery isn’t charging.

Loads that can affect what you see include:

  • Refrigerator controls
  • Furnace
  • Ventilation fans
  • Water pump
  • Lights
  • Inverter
  • USB chargers
  • Entertainment equipment
  • Other 12-volt accessories

Some of these loads cycle automatically.

That means solar may appear to work well one minute and poorly the next even though solar production itself hasn’t failed.

Try This

Turn off unnecessary 12-volt loads temporarily and check the solar readings again.

If battery charging suddenly looks much better, the solar system may simply have been keeping up with the RV’s electrical consumption.

Step 3: Look at Panel Input and Charging Output Separately

This is where troubleshooting becomes much easier.

Don’t look only at whether the battery says charging.

If your controller or monitor provides the information, look at:

  • Solar panel voltage
  • Solar input current
  • Controller output
  • Battery voltage
  • Charging stage

You’re trying to determine where the power disappears.

For example:

Panel voltage disappears when the problem occurs:
The problem may be on the panel/input side.

Panel voltage remains but charging stops:
Look more closely at the controller, battery condition, controller settings, or charging stage.

Controller is producing power but battery voltage isn’t responding as expected:
Battery condition, wiring, connections, or RV loads may need further investigation.

This is much more useful than simply looking at a charging icon.

Step 4: Check for Loose or Intermittent Connections

An intermittent connection can make an RV solar system particularly frustrating to diagnose.

The system may work perfectly while you’re checking it and fail again later.

Check accessible connections for:

  • Loose terminals
  • Corrosion
  • Damaged wiring
  • Poor crimps
  • Discoloured or overheated connections
  • Loose fuse connections
  • Loose breaker connections
  • Connectors that aren’t fully seated

Pay particular attention to connections between:

Solar panels → controller → battery

Movement while travelling can make a marginal connection become intermittent.

Safety Stop

Solar panels can produce electricity whenever they’re exposed to light, even if the RV is disconnected from shore power.

Do not disconnect, probe, or work on wiring unless you understand the system and can do so safely. Damaged, overheated, or high-current connections should be inspected by a qualified RV technician or electrician.

Step 5: Check Fuses and Breakers

Don’t assume a fuse is good simply because it looks good.

Depending on the installation, an RV solar system may have protection between:

  • Panels and controller
  • Controller and battery
  • Battery and distribution system

Also check any solar disconnects or breakers.

An overheated fuse holder, loose breaker connection, or poor terminal can sometimes work intermittently rather than failing completely.

Look for:

  • Heat damage
  • Discolouration
  • Melted plastic
  • Loose terminals
  • Corrosion

If something has obviously been overheating, don’t just keep resetting or replacing components. The cause of the overheating needs to be found.

Step 6: Does the Problem Appear After the System Gets Hot?

Temperature can provide another useful clue.

If solar consistently works when everything is cool but stops after operating for a while, pay attention to that pattern.

For example:

Works first thing in the morning → stops later → returns after cooling

That’s different from solar output simply declining because lighting conditions changed.

Possible causes can include:

  • Controller overheating
  • Poor electrical connection heating up
  • Protection circuitry activating
  • Component failure when warm

Check that the charge controller has adequate ventilation and isn’t surrounded by stored items that trap heat.

Don’t automatically replace the controller, though. Find the pattern first.

Step 7: Check the Charge Controller Settings

A controller that appears to stop charging may actually be doing exactly what it has been programmed to do.

Check that the controller is configured for the battery installed in the RV.

Battery types can include:

  • Flooded lead-acid
  • AGM
  • Gel
  • Lithium

Incorrect charging settings can cause confusing behaviour.

Also check whether the controller is showing:

  • Bulk
  • Absorption
  • Float
  • Standby
  • Fault or error indication

A controller entering float is very different from a controller losing solar input completely.

Step 8: Compare the System Under Similar Conditions

This is one of the best ways to troubleshoot an intermittent problem.

Instead of comparing:

8 AM yesterday to 3 PM today

try comparing the system under reasonably similar conditions.

For example:

Yesterday: clear sky, noon, battery at 70%, minimal RV loads
Today: clear sky, noon, battery at 70%, minimal RV loads

If output is reasonably similar, the large changes you’ve noticed at other times may simply be operating conditions.

But if the system produces normally one day and virtually nothing the next under similar conditions, you’ve learned something important.

Now there’s a reason to investigate the system itself.

What If the Problem Follows Shade or Weather?

Changing sunlight can cause dramatic changes in RV solar production, especially with permanently mounted panels.

But that’s a separate issue from an intermittent electrical fault.

If the system:

  • Drops when a shadow crosses the panels
  • Improves when the RV is moved into direct sunlight
  • Produces less during cloudy conditions
  • Changes considerably throughout the day

read Does Solar Work in Shade or Cloudy Weather?

That article explains how changing light affects solar production and why even relatively small shadows can make a surprisingly large difference.

What If the Controller Sometimes Says It Isn’t Charging?

Don’t condemn the controller based on the charging indicator alone.

First determine:

Is solar voltage reaching the controller?

Then:

Does the battery actually need charging?

And:

Is the controller deliberately reducing output because of battery voltage or charging stage?

If panel input is consistently available but controller output unexpectedly disappears when the battery needs charging, then the controller becomes a stronger suspect.

See: Solar Controller Says It Isn’t Charging the Battery? Here’s What It Means

When Intermittent RV Solar Is Probably Normal

Intermittent-looking charging is often normal when:

  • Battery state of charge changes
  • RV electrical loads turn on and off
  • Controller changes charging stages
  • Sunlight conditions change
  • The system enters float
  • You’re comparing readings taken under different conditions

Solar charging is dynamic.

You shouldn’t expect the same amperage every time you look at the controller.

When Intermittent RV Solar May Indicate a Real Problem

Investigate further if:

  • Solar input disappears in good direct sunlight
  • Output repeatedly drops to zero for no obvious reason
  • The problem occurs under repeatable conditions
  • Moving wiring or connectors changes the reading
  • A fuse holder or connection becomes hot
  • The controller repeatedly shows a fault
  • The system stops after warming up and returns after cooling
  • Panel voltage reaches the controller but expected charging repeatedly disappears
  • Solar performance suddenly changed and never returned to its previous behaviour

Those symptoms point more toward an actual system problem than normal solar variation.

A Technician Can Diagnose This Faster If You Record the Pattern

Intermittent problems are difficult when everything works normally by the time the RV reaches the shop.

Before booking service, take pictures of the controller or monitor when the problem occurs.

Record:

  • Time of day
  • Weather conditions
  • Battery voltage
  • Battery state of charge if available
  • Solar panel voltage
  • Solar current
  • Controller output
  • Controller charging stage
  • Any error codes
  • What major RV loads were operating

Then take another set of readings when the system starts working again.

That comparison can be extremely useful.

Instead of telling the technician:

“The solar works sometimes.”

you can say:

“At noon in full sun I still had 38 volts coming from the panels, but controller output dropped to zero while the battery was at 12.3 volts.”

That’s a much better starting point for diagnosis.

Bottom Line

If your RV solar works sometimes but not always, don’t start replacing parts until you’ve figured out what changes when the problem occurs.

Start with the battery state of charge and RV loads. Then determine whether solar input is reaching the controller and whether the controller is sending power toward the battery.

If the problem follows changes in sunlight, it may simply be normal solar behaviour.

If it happens under otherwise similar conditions—especially if panel input or controller output suddenly disappears—start looking for an intermittent connection, protection device, controller problem, or another electrical fault.

The goal isn’t just to prove that the solar system occasionally stops charging.

It’s to figure out where the power stops.

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Written by Dan Harvickson, RV troubleshooting specialist