Most experienced RV travelers will tell you that air conditioning is an absolute necessity.

Unless you are traveling n the mountains or camping n the winter, chances are you won’t get a good night’s sleep without a properly functioning rooftop RV air conditioner. 

Unfortunately, RV rooftop air conditioners are all too easy to forget about. Right up the moment when you have a problem.

If the mercury is rising in your RV and you are in a desperate spot, or you are simply trying to be proactive about the problem, you might be wondering what you can do if your RV’s air compressor isn’t coming on?

Fortunately, there are a few common RV rooftop air conditioner problems that you might be able to diagnose and repair yourself. Though there are also a few that truly need the services of a highly trained professional.

This guide will help you troubleshoot whether or not you can fix a problem with your RV’s rooftop air conditioner, to determine if you truly can do-it-yourself, or if it’s time to call in an air conditioner mechanic. 

What Are Common Signs Or An RV Air Conditioner Problem?

Some RV air conditioners will give you signs of an imminent problem. Though there are certainly sometimes when they seem to die inexplicably. 

  • Fan Runs But Warm Air Comes Out – This is usually a sign that the thermostat has detected the temperature is rising in the RV and triggers the system to run normally. The fan itself continues to run, but since the compressor won’t move freon,  there is no real heat exchange.

  • The RV Air Conditioner Does Nothing – This could be a sign of a problem with the thermostat or a blown circuit breaker causing the entire system to not work correctly. Sometimes something as simple as a dead battery n the RV’s thermostat control can be the culprit preventing the system from firing.

  • The Air Coming Out Is Stale and Air Flow Is Weak – This could be a sign of a few different problems. The RV air conditioner might be low on freon or you have a badly clogged RV AC air filter

How Does An RV AC Compressor Work

How Does An RV AC Compressor Work

To help better diagnose the problem with an RV air conditioning system, it helps to have an idea of how the system works.

With most RV’s the air conditioner system shares many components with the RV’s heating system.

An RV rooftop air conditioner has two main components: The compressor and the fan. The compressor runs off the RV’s onboard 12-Volt current.

It works by circulating a compressed refrigerant, which is usually, Freon, through a series of coils and special cooling fins.

This essentially exchanges the heat and humidity inside the RV. Though to do it effectively the RV air conditioner’s compressor relies on the fan to blow the cool air across the RV.

The entire air conditioner system is coordinated by the thermostat, which keeps track of the temperature and triggers the system whenever the temperature inside the RV rises to the set degree.

At that point, the thermostat then triggers the compressor and fan to turn on and off. Most RV thermostats rely on one or more capacitors.

They can also be powered by the RV’s onboard 12-volt electrical system or a battery. 

My RV’s Air Conditioner Compressor Won’t Start 

One of the most common signs of an RV air conditioner compressor failure is the thermostat showing that the system is active and the fan is running, but only warm, stale air comes out.

One of the first things to look at in a situation like this is the RV air conditioner compressor’s capacitors.

It is entirely possible that one or more of them might have overloaded and blow.

This prevents the electricity from completing the circuit thus preventing the air conditioner compressor motor from turning on.

Symptoms Of A Bad AC Compressor Capacitor Problem

Symptoms Of A Bad AC Compressor Capacitor Problem

The following are some common symptoms of a bad RV air conditioner capacitor. Some of these you can spot in advance, though some are more challenging. 

  • The AC system hums as it attempts to start but can’t initiate.

  • The air conditioner system runs for a few minutes and then stops, but doesn’t trip a circuit breaker.

  • The fan blades need a little push to get them started. 

  • The Air conditioner blows warm, stale air but the compressor does not function.

What Does An Air Conditioner Capacitor Do? 

All capacitors are designed to store a small amount of electric charge to help boost more powerful devices.

In the case of an RV air conditioner system, both the compressor and fan motor rely on capacitors to help get them started.  

In some cases, a bad capacitor can potentially explode without damaging any other components in the RV’s air conditioner system.

This sort of thing is especially likely to happen if your RV has gone unused for a long period of time.

If you can open a panel to see the internal guts of your RV’s air conditioner system a capacitor loos like a small battery or button, and on a larger unit you might see multiple ones throughout the system. 

What Does A Bad Air Conditioner Capacitor Look Like

What Does A Bad Air Conditioner Capacitor Look Like?

Let’s say you can get at the electronic guts of your RV’s air conditioner system to hunt down a suspected bad capacitor.

Sometimes you will notice signs of a burned-out capacitor in obvious black marks or a clearly damaged component.

Though there are times when an internal fault in a capacitor simply isn’t visually obvious.

If you don’t see any immediate visual signs, but you suspect a bad capacitor, you will need to check the suspected bad capacitor with a multimeter.

This involves touching the probes to a good capacitor’s prongs. When you do, the display will show a value that gradually decreases over time. This doesn’t happen when the capacitor is defective.

To replace the capacitor, you will need to look for the small model number printed on the side or top of the capacitor.

Then replacing it is simply a matter of using a soldering iron to loosen and remove the old one, then carefully applying it with the correct replacement and two very small dobs of melted electrical solder. 

Checking Other Components Of Your RV’s Air Conditioning Compressor

While air conditioner system capacitors problems are the most common culprit in a compressor failure, they are not the only thing to check.

Check The Air Conditioner’s Start Relays

Start relays can sometimes fail, thus preventing the compressor from firing. You might notice signs of burnout or the relay coming loose.

Burns, smudges, or debris can sometimes build up on the connections, which prevents the current from flowing through.

When this happens the start relay can’t get the compressor to engage. This is a relatively cheap fix if you are near a well-stocked auto parts store.

You can simply take the relay out and bring it with you. The identification numbers will be printed on it.

Check The Circuit Breaker Or Fuse Panel

Sometimes a circuit breaker can trip or a fuse can burn out, and still look like everything is fine.

Then when you give it a closer look, it’s clear that the trigger is indeed flipped or the fuse is indeed bad.

This simple little fault can prevent necessary power from getting to the air conditioner’s compressor. 

Compromised Valves

Broken or stuck valves can directly affect the functionality of an RV air conditioner compressor.

When this happens the refrigerant gets to the compressor inlet as a liquid rather than a gas. 

This is one of those things that ride the line between something you can fix yourself or if you need to call in a professional. 

Check The Air Conditioner Filter

A lot of RV air conditioner systems have an air filter in the air return. If you haven’t cleaned it in a while or ever, there might not be sufficient airflow coming back into the system.

Try replacing the filter or thoroughly cleaning it, if it’s a reusable filter. Then reset the circuit breaker connecting the RV’s air conditioner system to the onboard 12-volt power. 

How To Tell If Your Compressor Is Bad?

If you have gone through and checked the capacitors, the startup relays, and made sure the filters are clear, then chances are the fault is inside the compressor itself.

This could be something like a burned-out bearing or another mechanical failure that is beyond your control.

This is usually the point where you need to call in a professional mechanic to diagnose the situation. 

Especially if the compressor feels alarmingly hot smokes or shows outward signs of burn damage. These are usually signs of a major internal mechanical failure.

Frequently Asked Questions

Can Low Refrigerant Levels Can The RV AC Compressor To Fail?

Technically, yes an RV AC system that is very low or out of refrigerant will not produce cold air.

Though this is usually not something that jumps up and catches you by surprise.

Usually, an RV air conditioning system that is low on refrigerant will gradually perform worse and worse over the course of weeks or even months. 

Can I Just Use The Motorhome’s AC To Keep The RV Interior Cool?

While the motorhome’s dash AC might be able to keep you cool while you drive down the road, it will likely not be sufficient to cool the entire RV through the course of a long day or a hot night.

Not to mention the fact that you would have to leave the motorhome’s engine running all night long.

In a pinch, you might be able to get by doing this, with the strategic placement of a fan or two, but it’s not an effective long-term solution to an RV air conditioner compressor problem. 


RV air conditioner compressor problems are certainly a headache that you don’t want to let ruin your RV vacation.

While preventive maintenance will certainly help, there are none-the-less times when your RV’s rooftop air conditioner is going to have a problem.

Keeping a multi-meter onboard your RV at all times and some other basic tools like a soldering iron will go a long way toward diagnosing a problem and perhaps even repairing it yourself. 

Start by checking the fuse or circuit breaker for signs of a problem. Then give the filters and the thermostat a good hard look.

These are simple non-intrusive things that are easy to eliminate. From there, you can check the capacitors and the start relays to see if they show any obvious signs of a fault.

With a little luck, you might be able to fix your RV’s air conditioner compressor, without having to shoulder a spendy mechanic bill.