How to Test an RV Air Conditioner Capacitor

Summertime RVing isn’t complete without a working air conditioner to keep you cool on hot days. But A/Cs can malfunction, often due to a failed capacitor. Learning how to test and replace this inexpensive part can save you from sweltering or paying for an expensive RV technician visit. Follow this guide to diagnose and repair AC issues related to the capacitor. Soon you’ll be chillin’ in your camper again!

Why the Capacitor is an Important Part of an RV Air Conditioner

The AC capacitor plays a crucial role in starting the air conditioning unit and keeping it running properly. Here’s a primer on what this small component does:

• Provides startup voltage to the motors – The capacitor gives the initial jolt of energy needed to get the compressor and fan motors spinning when the AC turns on. Without this extra voltage boost on startup, the motors would just strain and buzz but not actually begin operating.
• Stabilizes current for the motors – In addition to starting voltage, the capacitor helps stabilize the electrical current flow to the motors while running. This prevents them from overheating and drawing excessive amperage that can trip breakers or blow fuses.
• Prolongs motor life – By regulating voltage and current, the capacitor extends the lifespan of the compressor and fan motors. Fluctuating power supply and running over ampacity burns out windings prematurely.
• Acts as a voltage “reservoir” – The capacitor stores energy like a battery and releases it as needed to smooth out voltage fluctuations to the motors. It kind of acts like a shock absorber for the A/C’s electrical system.
• Reduces compressor cycling – With a capacitor supplying steady power, the compressor doesn’t have to turn on and off as frequently. This makes cooling more efficient and reduces wear.

So in summary, the capacitor is vital for proper starting, smooth running, and longevity of the air conditioner motors. When it fails, the whole A/C suffers.

Signs Your RV Air Conditioner Capacitor is Bad

How do you know if the capacitor is the culprit behind your non-working or underperforming RV AC? Here are key signs to watch for:

• AC doesn’t turn on – If the air conditioner is completely dead when you flip the switch, the capacitor could be to blame. The most obvious symptom of a bad capacitor is the unit not starting up.
• AC turns on but shuts off repeatedly – If the air conditioner starts up but then cycles on and off after running just a short time, the capacitor may be unable to provide consistent voltage to the motors. This intermittent operation points to capacitor failure.
• Fuse blows or breaker trips when AC runs – A bad capacitor that isn’t properly starting the motors can cause the air conditioner to draw extra current leading to blown fuses or tripped circuit breakers.
• Buzzing or humming noise from AC but won’t start – Ever flip on your AC and just hear an annoying buzzing sound? This typically means the capacitor is trying but failing to start the motors.
• Fan motor runs slowly – With inadequate voltage from a faulty capacitor, the fan motor can run slowly. This causes weak airflow from the vents. The compressor also strains to run due to low voltage.
• Minimal cooling or cold air from vents – Problems with refrigerant flow from a overworked compressor with a bad capacitor affects the AC’s ability to cool properly.
• Capacitor is bulged, leaking, or has corrosion – A visual inspection revealing physical damage like a bulging can, green crusty discharge around terminals, or split plastic case indicates it needs replacing.

Any of these glaring signs point to a capacitor that should be tested further and likely replaced. Catching the issue early prevents more extensive AC repairs down the road.

Step-By-Step Guide to Testing an RV AC Capacitor

Alright, those symptoms have convinced you the capacitor is faulty. But how exactly do you test it to confirm? Follow this straightforward process:

Gather Tools and Supplies

To thoroughly test an air conditioner capacitor, you’ll need:

• Digital multimeter – This is essential for checking capacitance, resistance and continuity. The inexpensive basic models work fine.
• Insulated (plastic handle) screwdriver – Required for safely discharging the capacitor before handling.
• Gloves and eye protection – For safety when working with electrical components.
• Replacement capacitor – Have a new unit matched to your AC’s specs on hand in case the old one fails testing.
• Camera or phone – To take photos of the wiring before disconnecting anything, for proper reassembly.

And of course, basic hand tools like pliers, wrenches, wire cutters, etc. With the right gear prepped, it’s go time!

Shut Off Power to AC Unit

This step is crucial for safely accessing the capacitor and electrical connections:

• Locate the circuit breaker powering the RV air conditioner and switch it OFF.
• On some models, also unplug the exterior AC unit from the power cord inlet.
• Use a non-contact voltage detector to double check power is off before proceeding.

De-energizing the capacitors before disconnecting wires significantly reduces shock risk. Don’t skip this step!

Discharge the Capacitor

Before removing the capacitor, discharge any remaining voltage stored in it:

• Use the insulated screwdriver to briefly “short” across the terminals, connecting positive and negative.
• This drains any charge and voltage present. You may hear a pop or see a spark when shorted.
• Verify no voltage remains with a multimeter prior to handling.

Discharging the capacitor helps prevent nasty shocks, sparks, and damage to your multimeter.

Remove Wires and Capacitor

Next, disconnect the capacitor so it can be tested:

• Label wires or take photos to remember where they connect.
• Remove each wire connecting to the capacitor terminals.
• Unmount the capacitor from the AC frame and take it out.
• Inspect for any signs of damage like bulging or leaks.

If replacing, the new capacitor must be wired exactly the same way. Taking notes avoids mix-ups.

Inspect Capacitor and Note Rating

Before breaking out the multimeter, inspect the capacitor:

• Find the capacitance rating printed on the side, typically expressed in microfarads or “uF”.
• Note the voltage rating also listed, such as 370VAC.
• Record the capacitor model number to aid sourcing a replacement.
• If markings are unreadable, the capacitor is likely toast and should be replaced.

Having the original rating and model number is extremely helpful for finding an exact replacement match.

Use Multimeter to Check Capacitance

Now to actually test the capacitor’s capacitance value:

• Set your multimeter to capacitance mode, usually in the nanoFarad/microFarad range.
• Place the probes across the capacitor terminals. Doesn’t matter which probe goes to which terminal.
• Note the capacitance reading on the multimeter display.
• The reading should be close (+/- 10%) to the uF rating printed on the capacitor.
• If much lower than the rated spec, the capacitor is not functioning properly and should be replaced.

The tested capacitance reveals if the capacitor is operating within normal parameters.

Use Multimeter to Check Internal Resistance

Testing the equivalent series resistance (ESR) also indicates capacitor health:

• Set your multimeter to resistance mode, signified by the Ohm symbol.
• Place probes on capacitor terminals and note resistance measurement.
• Check manufacturer’s guidelines for allowable ESR range.
• ESR value significantly higher than spec means the capacitor should be replaced.

High internal resistance causes excess heat and electrical “leaking”, reducing performance.

Use Multimeter to Check for Continuity

The continuity test detects internal shorts and leakage:

• Set multimeter to continuity or resistance mode again.
• Place probes on capacitor terminals.
• Good capacitor should show open circuit. Any tone or zero Ohms means it’s bad.
• Short circuit = immediate replacement needed. Danger of serious issues if installed.

Continuity confirms any breakdown of internal insulation that should prohibit use.

Visually Inspect Capacitor

Finally, take a good visual look at the capacitor:

• Damage like a bulging or split casing indicates failure.
• Dried out, bulky internals also a red flag.
• Any leaked oil or corrosive buildup warrants replacement.
• Heat damage like melted plastic a sure sign to toss it.

If it can’t pass the eye test, the capacitor is already toast regardless of probe measurements.

With all tests complete, you should have a definitive answer on whether that capacitor needs to be swapped out or not.

Time to put your results into action!

Replace Defective Capacitor

If testing conclusively finds the existing capacitor faulty, now is the time for replacement:

• Install new capacitor with identical capacitance and voltage ratings as original.
• Ensure wiring terminals match exactly to avoid reverse polarity damage.
• Use photos or labels to reconnect wires to proper terminals. Double check orientations.
• Securely mount replacement capacitor in same position as old one.
• Restore power and test operation. Monitor current draw if issues persist.

Installing the new component and verifying smooth operation wraps up the repair.

Reinstall Functional Capacitor

If the thorough testing deems the capacitor still functional, reinstall the original:

• Carefully discharge before reconnecting any wires.
• Attach all wires to proper terminals according to labels or photos.
• Secure capacitor mount. Don’t overtighten.
• Restore power supply to AC unit.
• Power up system and confirm normal operation.

Assuming it checks out fine electrically, a capacitor in good physical shape can be reused.

Following this capacitor testing process empowers you to make the right repair decision and take action to get your RV air conditioner running optimally again.

How to Safely Discharge and Dispose of Capacitors

Before testing or replacing a suspect capacitor, it’s imperative to safely discharge it. Capacitors hold dangerous voltage charges even when power is shut off. Here are proper procedures for draining and disposing of capacitors:

Discharge Capacitor Before Testing or Removal

As emphasized in the testing process, an insulated screwdriver should be used to “short” across the capacitor terminals to drain any remaining voltage before disconnecting wires or handling. This prevents shocks, sparks, and multimeter damage.

Discharging is also essential for safe capacitor disposal, covered next.

Allow Time for Self-Discharge After Removal

Once disconnected from power supply, a capacitor naturally “bleeds off” voltage over time. To ensure it fully self-discharges:

• Leave capacitor disconnected for at least 5 minutes after removal from AC unit.
• 20-30 minutes even safer if capacitor rating over 40uF. The bigger, the longer to discharge fully.
• Use a voltmeter to verify 0 voltage between terminals before handling.

This waiting period lets any remaining energy dissipate safely.

Insulate Terminals Before Disposal

Prior to discarding bad capacitors:

• Confirm zero volts with a meter before proceeding.
• Place damaged capacitor in thick plastic bag. -Alternatively, wrap bare terminals with electrical tape for insulation.
• This protects against accidental contact when discarding.

Bagging or taping caps provides a shield against surprise shocks.

Follow Proper Capacitor Waste Disposal Methods

Check local regulations regarding capacitor disposal. Recycle or discard appropriately:

• Some types of old capacitors contain hazardous materials requiring special waste handling. These may need to go to household hazardous waste collection sites.
• More recent AC capacitors are often non-PCB and can go in normal landfill-bound garbage.
• Many scrap metal recycling centers accept intact aluminum cased capacitors as scrap aluminum. Call yours to see if they take capacitors.
• Do not put old capacitors into fires or incinerators as toxic fumes may be released from burnings.

Following safety protocols for disposal ensures these electrical components don’t end up in the wrong place.

Handlingcapacitors with caution and using protective gear like gloves and eyewear is also wise. Take your time and put safety first!

What’s the Cost for Replacing an RV Air Conditioner Capacitor?

Okay, the verdict is in – that old capacitor definitely needs to be replaced. What’s the damage to your wallet going to be?

Here’s a look at typical costs:

Capacitor Part Cost

The replacement capacitor itself ranges from about $20-60 from RV parts suppliers. Higher voltage and capacitance ratings do cost more. But expect to pay less than $100 even for larger A/C unit capacitors.

You can sometimes save a few bucks with generic capacitors, but OEM is recommended for proper specifications.

DIY Labor Cost

One of the biggest advantages of replacing the capacitor yourself is avoiding high labor charges. Plan on 1-2 hours for the entire DIY process:

• Disassembling the AC shroud: 30-45 minutes.
• Testing and replacing capacitor: 15-30 minutes.
• Reassembly: 30-45 minutes.

With some experience, it may only take about an hour total.

HVAC Service Call Cost

If hiring an RV service tech to replace the AC capacitor, expect to pay around $125-250 for typical service call fees.

This covers the technician’s drive time, diagnosis, part cost, installation, and testing. You’re paying for their expertise and efficiency.

Total Replacement Cost Comparison

Replacing it yourself clearly costs significantly less than paying for professional service. But for some, the RV technician provides valuable peace of mind.

Either way, repairing a bad AC capacitor is a much cheaper fix than replacing the whole air conditioner unit!

Selecting the Correct Replacement Capacitor

Choosing the right replacement capacitor ensures proper operation of your RV air conditioner. Matching key specifications avoids damaging mismatch issues.

Here are the critical factors to consider when sourcing a new capacitor:

Match Capacitance Rating

The capacitance rating, valued in microfarads (uF), must be matched to the original part. This determines how much “load” the capacitor can handle. Too low results in insufficient voltage. Too high strains the electric system.

Match Voltage Rating

Similarly, the voltage rating on the new capacitor must equal the old one. Typical values are 370VAC or 440VAC. Insufficient voltage rating stresses the capacitor. Excessive voltage shortens its life.

Match Capacitor Frame Size

The replacement must fit properly in the allotted space. The frame size code gives the dimensions. Example 5MINM450VAC.

Verify Number of Terminals

Some RVs use dual run capacitors with 2 terminals, others use separate start and run caps with 3 terminals. Replace same style as original.

Use Identical Terminals and Mounting

Where wires connect and how it mounts also must align with the capacitor being replaced to work properly.

Consult the OEM Part Number

Ideally, source an exact OEM spec capacitor made specifically for your AC make and model. Cross-referencing against manufacturer’s part number when ordering prevents mismatches.

With the huge variety of capacitors, an accurate match is essential. Don’t skimp here!

Potential Issues Beyond a Bad Capacitor

While the capacitor is a frequent failure point, your RV air conditioner may have other underlying issues if replacing the capacitor alone doesn’t resolve problems.

Here are some possibilities to check out:

Power Supply Issues

• Low voltage from campground hookup to AC unit
• Tripping breaker or blown fuse from excessive current draw
• Faulty wiring connections causing voltage drop

Electrical Shorts

• Burnt or damaged internal wiring
• Compressor or fan motor windings shorted
• Defective starting components like relays or contactors

Refrigerant Problems

• Low refrigerant level leading to reduced cooling
• Restriction or leak in refrigerant flow path
• Compressor not pumping efficiently

Air Flow Obstructions

• Clogged or dirty air filter
• Blocked condenser or evaporator coils
• Stuck or failed condenser fan blade

Control Failures

• Faulty thermostat
• Failed pressure switches or sensors
• Bad control board or blown fuses

Mechanical Issues

• Seized, burned out, or damaged compressor
• Sticking fan motor bearings
• Broken fan blades or damaged shroud

An RV technician has the skills and tools to troubleshoot and diagnose issues extending beyond capacitor failure. Don’t hesitate to seek professional service if replacement doesn’t resolve lingering AC problems.

When It’s Time to Replace the Entire AC Unit

In some cases, the cost and hassle of repairing an old failing RV air conditioner reaches the point where investing in a new unit makes more sense.

Consider replacing rather than repairing if:

• You’ve already sunk money into repairs but problems return quickly. Don’t keep throwing money at an AC sinking fast.
• The compressor is mechanically locked up and won’t turn freely. Burnt windings also a goner.
• Significant refrigerant leaks make recharging cooling impossible. Major leaks mean corroded coils and other damage.
• Electrical shorts, burned wiring or components present fire hazards and can’t be rewired reliably.
• Parts like blower motors, capacitors, and control boards are obsolete and unavailable.