Tips For Working On Your RSX AC System (And Most Other Vehicles)
I've worked on a lot of AC systems, and it's a science and art of its own within car repair. Once you understand how it works, it can be much less intimidating and easier to find a problem you might be having. While you might have a car other than an Acura RSX, the information is still valid and will help you out. This is meant to compile information that I had trouble finding when I was new to the RSX's AC system.
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Prologue: AC Can Be Dangerous
AC refrigerant, also known as R-134A in modern cars (and Freon if you call tissues "Kleenex") is a gas kept at high pressures. It's also really bad for the environment, as sunlight converts it to chlorine and bromine gas, which is poisonous to you and depletes the ozone that protects you from radiation. You can also be fined up to $50,000 for releasing it into the atmostphere. If you're going to remove a component of your AC system, go to a local repair shop with an evacuation machine to remove the refrigerant. It only costs about $35-50 to have it done. There are also ways to reclaim your own refrigerant easily, but they start becoming worth it only if you're doing AC work as a side hustle due to expense.
1. Refrigerant Does Not Go Bad / You Do Not Need A Recharge
I've seen so many people assume that they need to go to the store and pick up an "AC Recharge Kit" from any number of retailers. It's an easy mistake to make, but in my opinion it's a predatory product that preys on people who are tired of not having AC and just want a chance at it working again while actually lowering the chances significantly that the AC will work correctly again.
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| Don't Use These |
The science behind these cans doesn't add up. Refrigerant doesn't go bad, so the reason your AC probably isn't feeling as cold as it used to be is that there's a leak at one of the o-rings in the system. The refrigerant recharge cans have leak sealer in them, but that can create more issues than it solves. The chemicals used to do this react to temperature differentials or moisture depending on design, so if you have a leak and moisture has probably gotten in, you may end up creating blockages in your AC system that will make the repair even more difficult. A lot of AC shops won't connect your AC up to their machines if you've used a leak sealer because it can break them.
You need to be able to watch both the low and high pressure side of the AC system to make a proper diagnosis. These cans connect up to the low pressure side only, so compressor and expansion valve issues can hide from you. When you add refrigerant through these, you're doing nothing about the moisture in the system that needs to be removed, and you don't know how much refrigerant is in the system. If you add too little, it won't turn on. If you add too much, it won't turn on, or it will damage the AC system.
These cans just aren't a good idea for so many reasons. Read on to find out how you can do it the right way!
2. Take Notes
AC system issues can be pretty complex, and span across different systems in the car. Take some notes on your phone, laptop, or a good old notepad to keep track of what you've done and what is ruled out. It can be easy to go down the wrong rabbit hole unless you keep impecable data, so start taking notes now!
3. Look For Clues
Luckily enough, there are some things you can check that don't require disassembling your car. The car should be turned on, running, and warmed up for all of these tests.
- Climate Controls - Do turning any of the knobs or pressing the buttons do anything? If not, you might have an issue with fuse 14, something unplugged behind the climate control panel, or wiring.
- Blower Motor - Turn on the fan in your climate control system. Does it blow air at you? If not, it could be a fuse, relay, blower motor transistor, or wiring.
- AC Condenser Fan - Turn on the fan in your climate control system to any value other than off, and then press the AC button. Open your hood, and look at the back of your radiator. One fan spins to cool off the radiator, the other one spins to cool it off when your AC is taxing the system. Do both fans come on? If not, you may have an issue with a fuse, relay, fan, or wiring.
- Compressor Clutch - Stand in front of your car with the hood open. Look to your left. Underneath the power steering pump and your alternator is your AC compressor. If you have someone in the car turn the AC on and off with the fans on any value except off, you'll hear the click of the relay and the compressor clutch engaging if everything is working properly. You'll see the AC compressor's pulley fully engage and disengage as they turn it on and off. Once you see it, it'll make sense. If it doesn't do this properly, or under certain conditions, you may need to rebuild your compressor clutch (budget option) or get a new AC compressor (expensive option), but check the fuses and relays associated with it (listed below) first.
- Cabin Air Filter - If you pop the rollers off your glovebox, behind it is the container with your cabin air filter. Carefully remove both of the filter media and check them for excessive dirt, rodent poop, leaves, or anything else nasty. They can make it harder for your AC and heating systems to blow the air through the car.
- AC Condenser - Your AC Condenser is the metal thing that looks like a small radiator in front of your radiator. You can get a good view by looking through the front bumper. Does it look undamaged? If not, it may be the source of a leak.
4. Check Your Fuses And Relays Before You Refill Your AC
While fuses generally don't blow for no reason, they can be an important diagnostic tools. Make sure they don't look burnt, and measure the resistance across them with a multimeter. They're easy to check and there's just a few of them (with #14 being the most important) so it's an easy thing to go through. You're going to want to check the following:
- Under-Dash Fuse 14 (10A) Most of Climate Control System 12V with key in on position
- Under-Hood Fuse 1 (30A) Compressor Clutch Relay, Condenser Fan Relay 12V at all times
- Under-Hood Fuse 12 (40A) Blower Motor Relay 12V at all times
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| Under-Dash Fuse Box |
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| Under-Hood Fuse Box |
Relays are physical switches in a plastic case. You can hear them physically click on or off depending on their power state. Like all moving parts, sometimes they can get stuck open or closed and not work as expected. Checking the relays is a little different than checking fuses, but you should be able to isolate the problem more after you've checked your fuses. All relays related to the AC are in the under-hood fusebox:
- Relay 2 (5R), AC Compressor Clutch
- Relay 4 (3R), Blower Motor
- Relay 9 (8R), Condenser Fan
To check relays, you can remove the one you think is applicable from the car, and check continuity (resistance) across the pairs. 1 and 2 should be open, and 3 and 4 should show continuity.
If you have a lab power supply, or you have some test leads you can use to connect the relay to the battery, you can switch the relay on and off by touching the test leads separately to 3 and 4.
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| Standard Relay Pinout Found On The Acura RSX |
You can also manually test the relay's circuits by using a relay test kit. It will allow you to manually turn on and off certain circuits in the car to see if they work.
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5. Get Some Manifold Gauges And An AC Vacuum Pump
These tools are the fork and knife of the AC technician. They'll allow you to measure what's going on in your AC system easily, vacuum out moisture, add oil and UV reactive dye for diagnosing leaks, and refill your car with refrigerant. Sometimes you can rent these items from a local autoparts store. I had multiple cars without working AC, so I just bought the kit.
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| Manifold Gauges |
The usual pressures you'll see are 25-55 PSI on the low side, and 135-345 PSI on the high side. This depends on temperature, but all car AC systems using R-134a should reflect this while working properly.
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6. Use UV Reactive Dye To Find A Leak
In order to find leaks in AC systems, the general process is to evacuate the system, put the correct amount of refrigerant in according to the service manual, and also add some UV-reactive dye. This type of dye will flouresce under a UV light (black light). You don't need much, and it will very clearly show you where a leak is if there is one. You can follow the path of the AC system and look for dye throughout at any of the connection points in the system, and on the surface of the AC condenser.
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| AC Line Leak |
Another method of finding a tiny leak is to use an AC leak sniffer. They're electronic devices that can detect the presence of refrigerant fumes in the air.
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7. How To Tell If Your Compressor Has Failed
Compressors only fail for a couple reasons. One of those is an issue with a fuse or relay related to the AC compressor or the AC compressor clutch, like I mentioned earlier.
The second reason is one of the safety switches are being tripped or broken. This can be the low-pressure cutoff switch or, the high-pressure cutoff switch generally. You can generally check the pressure in the system with manifold guages to determine if the pressures are too low, or if they're too high. If the sensor itself is broken, you might need to take it out of the compressor and test it.
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| AC Compressor Parts |
The last reason they fail is the clearance for the compressor clutch growing too large. The AC compressor clutch is an electromagnetic system that brings the pulley closer to the clutch. Over time this gap gets larger as there's wear on the system. You can buy a new compressor clutch and replace it instead of spending big money on a new compressor entirely.
Additionally, since compressors have seals they can become weaker if they fail, but usually that involves a catastrophic AC failure. Catastrophic failure includes a seized compressor, damaged bearings, or broken rotors.
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8. What To Replace When A Component In Your AC System Has Failed
Any time you open up your AC system, you're letting in moisture.Water can't be compressed, so it will make your AC system not work correctly, or at all. The way AC systems deal with moisture is with a refrigerant dryer. It's a cylindrical metal container in your engine bay with dessicant (like kitty litter or silica gel) that absorbs excess moisture. Any time you open up your AC to work on it and you don't immediately plug any open lines, you'll need to replace your AC dryer.
Additionally, if your compressor fails dramatically, you need to replace your AC dryer and your AC condenser. If any metal fragments are lodged in either one of these components, it can lead to a quick failure of your new AC compressor.
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9. When You Find The Leak
Congrats! You found a leak. Now, you should replace the o-ring that caused it. There's a couple o-ring types that are popular: Nitrile Butyl Rubber (NBR), Ethylene Propylene Diene Terpolymer (EPDM), and Hydrogenated Nitrile Butyl Rubber (HNBR). The only ones you should use in an AC system are HNBR o-rings, which can be identified by their green color. There's kits online of them which are really helpful so you don't have to keep ordering expensive OEM o-rings one at a time.
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10. So... Where's The Thermal Expansion Valve?
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| RSX Thermal Expansion Valve, Removed from Heater Core Assembly |
In an AC system, there's normally something called a thermal expansion valve (TXV). This part is responsible for regulating the flow of refrigerant through the system. Given that it's a valve (moving part) with a small oriface, it can be the cause of clogs if the system is contaminated. However, the service manual doesn't mention anything about it and it's not included in any parts diagrams. This is where it is:
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| Thermal Expansion Valve Location Circled In Yellow |
It's possible to remove this part without removing the dashboard with some tight maneuvering in the engine bay, but unfortunately it didn't seem possible to put a new one in without scratching the machined mating surface, so I recommend removing the dashboard if you diagnose it as the problem.
Acura Part Number: 80220-S6A-013
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I'll be writing an actual guide on how to fill and diagnose an AC system in depth, but this is a great way to check the easy stuff and get the tools you need to start making progress. I put it out because I've seen an incredibly large need for it in the RSX community, as well as other car communities, and I think just this info will be extremely valuable to them both. Good luck!
Disclaimer:
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