Air Conditioner Only Works When Car is Moving   


Beating the summertime heat (and the humidity) with a perfectly climate controlled interior in your vehicle is one of life’s simple pleasures.

Unfortunately for a lot of car owners they find out – often in the middle of the summer’s worst heatwave – that their air conditioner isn’t behaving when they need it most.

It’s tough to think of anything more uncomfortable than sliding into a hot, sticky, humid car with an air conditioner that decides to only work when the vehicle is moving.

With a little bit of help – and this detailed guide – you won’t have to worry about that nightmare becoming your reality anytime soon, though.

Ready to get into it?

My Air Conditioner Only Works When Car is Moving – What’s Wrong?

Most of the time when your air conditioner is on the fritz it’s a simple and straightforward solution that will get you back up and running.

At the same time, though, you need to be able to quickly diagnose exactly why your air conditioner is misbehaving if you’re going to have any chance of fixing it in a hurry and beating the summertime heat.

We run through a couple of the most common reasons your air conditioner isn’t working unless your vehicle is in motion below to help you out.

Issues with Your AC Condenser Fans

One of the most common issues responsible for creating this problem is that your AC condenser fans just aren’t kicking on automatically the way they should be.

Condenser fans play a huge part in making sure that heat in the refrigerant system gets transferred into the exterior of your vehicle rather than leaving it inside of the engine compartment – or the AC system itself.

These condenser fans (generally) are designed to kick in as soon as the engine hits its optimum operating temperature. That’s usually somewhere between 195°F and 220°F (though it depends on the make and model of your car).

If there’s something screwy with your condenser fans, though, or the sensors responsible for detecting those temperature levels they might not kick on at all.

When that happens you’ll be lucky if your air conditioner works even just a little bit – while you’re driving or while you’re parked, it makes no difference!

Check the relays and the fuses for your condenser fan to see if something has gone sideways there. A quick fuse replacement might be all you need to get back up and running.

Not Even Coolant/Refrigerant in the System

Sometimes, though, the reason that your AC isn’t kicking on is because you have a low refrigerant charge in your air conditioning system.

Most manufacturers today take advantage of low pressure switches in the AC unit to guarantee your compressor doesn’t run all the time, especially if refrigerant levels are low.

Unfortunately, from time to time, the sensors and switches are a little more sensitive than they have been designed to be. You end up dealing with a malfunctioning AC unit that doesn’t want to turn on just because of a slight dip in refrigerant charge or coolant.

The quick fix here is to check your coolant levels, check your refrigerant charge, and make sure that your pressure switches and sensors are in fine working order. If anything needs to be replaced you’ll need to tackle that straightaway or your AC is going to continue to misbehave.

Compressor Clutch Issues Causing a Delay

Now we are getting into slightly more advanced problems that your AC system might be dealing with, the kinds of problems you’ll want mechanics to take a look at.

Compressor clutch components are responsible for engaging the compressor shaft in your AC unit, pumping refrigerant throughout the system and helping you enjoy perfectly cooled down air on demand.

A great test to figure out whether or not the clutch is operating the way it should be is to turn your air conditioning on full blast and then revved the engine a little bit.

If the compressor “follows” the revving engine – it kicks into gear as the RPMs accelerate but then starts to drop off as the RPMs decelerate – the chances are pretty good you’re dealing with a fault in the system.

Your clutch is probably going to need to be replaced and that’s not always something that vehicle owners are comfortable tackling.

By all means, watch a couple of YouTube videos to figure out if this is something you can handle all on your own. But if you feel like it’s outside of your realm of expertise or outside of your comfort zone there’s nothing wrong with having a mechanic fix it for you.

Compressor Needs to Be Cleaned or Maintained – Maybe Even Replaced

Of course, sometimes the compressor clutch (and the compressor itself) just needs to be deep cleaned, refreshed, or maybe even replaced altogether.

This is something every car owner can handle on their own with a quick Google search or after watching a few YouTube videos.

Replacing a whole compressor (not just the compressor clutch) is easy enough for almost anyone to tackle on their own, too.

You’ll know if your compressor has to be swapped out after cleaning it if you’re noticing any leaks on the AC line, near the actual condenser itself, or on any of the condenser coils.

Debris Could Be Gumming Up Your AC Vents

The last thing you want to be on the lookout for if your air conditioning won’t turn on until your vehicle is moving down the road is an obstruction in your AC vents.

It might be that there is something obstructing the airflow coming from your air conditioning system into the cabin, and all you need is a little bit of “extra pressure” powered by the revving engine to blow that obstruction free.

Sometimes, though, the obstruction is so entrenched that you actually have to go in yourself and fish it out. Luckily, obstructions like this are generally pretty easy to spot, even easier to locate, and pretty easy to pop out with a little bit of wire or a something similar.

Recent Posts