My wife’s car’s A/C is not cold, so as a first step I’m going to see if recharging the A/C fixes the problem.

‘Recharging’ the A/C refers to adding more refrigerant to the system. This is amazingly enough a service you can perform on your car by yourself. They sell the bottles of refrigerant at most car stores and also at Harbor Freight.

It must be noted that your A/C shouldn’t ever be low on refrigerant - it’s a closed system. If there’s a lack of refrigerant it means there’s a leak and even if you add refrigerant it will slowly continue to leak out and you’ll be in the same place again. Apparently though, the recharge canisters they sell have something in them that seals small leaks so there’s a chance you can get away with this by itself.

These steps are specific to my make and model of car but might provide some pointers to you for doing it yourself.

Parts Needed

Tools Needed

  • Gloves
  • Thermometer
  • Headlamp

Notes

The refrigerant in cars is R-134a since ~1993-1995. Freon was in use before but you can’t get that anymore.

They really don’t make this process easy, do they? My dad always threatened torture if he ever got his hands on the mechanical engineers who designed his tractors because maintenance was so difficult. It’s the same here. What are the issues?

  1. The low-pressure recharge port is stuck way down under the hood and it’s right next to the main fan AND it’s nestled among things that get really hot when the car is running. See the picture below. Considering that you have to recharge the refrigerant while the car is running, this is problematic for your hands. Indiana-Jones levels of danger
  2. Since the recharge port is so far down under the hood, there’s no room to rock the can back and forth as they recommend in the videos and there’s barely enough hose on the canister to reach the port anyway.
  3. For the life of me I couldn’t be 100% sure of which of the spinny things under the hood was the compressor. I saw lots of spinny things and saw spinny things near where the refrigerant lines went and I assume one of them was the compressor and it was spinny, but they were all spinny all the time so I was a bit lost.

Once you remove the protector tab from the refrigerant canister and put the gauge on it you CANNOT unscrew the gauge from the canister until the canister is empty because all of the remaining refrigerant will escape into the atmosphere (I’m told this is an illegal thing to do).

The gauge that comes with the canister can be reused - you can buy gauge-less cans of refrigerant at Harbor Freight and probably elsewhere.

Warnings

DO NOT OVERFILL THE A/C SYSTEM WITH REFRIGERANT - You’ll have to take the car to the mechanic to fix that for sure.

Lots of things under the hood of a car are hot! They’ll burn you! Other things are moving fast and may cut you/break your fingers. Please practice safety!

Pre-Steps

Pop your hood and identify the following:

  • Low pressure charging port - It’s on a coolant line (metal pipe) and has an ‘L’ on it.
  • Compressor - This is a belt-driven thingy that spins when the A/C is on. The coolant lines should converge on it in case you find the charging port.

Steps

  1. Take the gauge off of the recharge canister.
  2. Rotate the temperature dial around the gauge to match the outside temperature - this tells you the proper maximum pressure you can put in the system.
  3. Take the cap off of the low pressure charging port and connect the connector from the refrigerant canister: pull up the collar on the connector and push it down on the port down until you hear a ‘tsssht’ sound of pressurzied gas escaping, then let the collar lower.
  4. Turn the car on and let it get up to temperature. I was able do this with the car parked and it only took a minute or so.
  5. Turn the A/C on all the way, max blower and open the doors. The idea here is to get the A/C to run as much as possible to ensure that you can see the compressor running.
  6. Take a temperature reading right of the ‘cold’ air from the A/C for reference.
  7. Watch the pressure gauge: when the compressor is off, it should read very high pressure. When it’s on, the pressure goes down. You should see this very discrete on/off behavior on the pressure gauge. If the pressure when the compressor is not in the nominal range as show by the gauge, you need a recharge.
  8. If you need a recharge, shake the refrigerant canister vigorously and then thread it on to the gauge.
  9. While the compressor is running (low pressure reading), squeeze the trigger for ~5s at a time and monitor the pressure when you release the trigger. Rock the canister back and forth while you hold the trigger. Get it as close to 40psi (or whatever the temperature-adjusted range on the gauge tells you) as you can without going over (we’re following the Price is Right rules). Seriously, do NOT risk going over: if the system is overcharged with refrigerant the compressor will not run and you’ll have to take it to the shop to bleed off the excess refrigerant.
  10. When the pressure is near max, take another temperature reading of the air from the vents: it should be colder now.
  11. Turn the car off, disconnect the canister and put the cap back on the recharge port.

Notes/Observations/Difficulties

When I hooked the gauge up to the low pressure recharge port it read well below the nominal range for the given temperature and it did so consistently. This was problematic as everything I had read indicated that the pressure should read very high when the compressor was off and then go back down when it turned on, but this reading was consistent. That was concerning, but since I was fairly sure the compressor was runnining all the time it at least made sense. I started to add refrigerant to the system by holding the trigger for 5s at a time and then checking the pressure. What started to not make sense was that as I added refrigerant to the system, the pressure reading was not consistently rising: it would wiggle around near the 35psi mark (which was outside the nominal range for the ambient temperature) no matter how much I added.

At this point I feared I had not hooked the canister up to the recharge port correctly, so I turned off the car and worked to re-seat the connector on the port. I turned the car back on and then, strangely enough, began to see the high pressure/low pressure behavior of the compressor kicking on and off. The low pressure reading was still not near the max of nominal, so I continued adding refrigerant while seeing no significant improvement.

At some point I felt that I had put enough in (I feared over-filling the system) and the can was getting pretty light, so I stopped and assessed the temperature of the air coming out of the vents. It was cold - NICE and cold. After getting my wife to confirm it was to her liking I turned the car off, cleaned up and congratulated myself on a job well done.

Naw, just kidding. I still felt something was off so I took the car on a short drive with the A/C running full blast. It was NOT cold in the least. At this point I was sure that I had overfilled the system because if you do that, the compressor won’t turn on. I even thought I heard the compressor trying to click on to no avail. Dejected, I took the car back and decided to take it to the shop in the morning first thing for them to look at.

So when the morning rolls around I get it to the shop first thing and of course on the drive over the A/C was perfectly frigid. At this point I’ve pretty much confirmed in my head that there’s an intermittent problem (perhaps electrical?) with the compressor that prevents it from kicking on in certain circumstances. The difficulty with intermittent problems is getting them to occur consistently enough to be diagnosed: you almost never can. The guy at the shop confirmed that it would be a waste of time to try to diagnose such an issue while it wasn’t occurring, but offered to do a quick check of the system to make sure everything was nominal. Fearing that I had somehow abused the A/C, I agreed.

It turned out that despite my best efforts the night before, the system was still low on refrigerant! At least this was consistent with the last set of readings I was getting from the gauge, but it was still troubling. There were several possibilities:

  1. The A/C system was largely empty of refrigerant and I did a good thing by filling it up. The evidence in favor of this is that I (think) I emptied nearly a whole can of refrigerant into the system and it was still low coupled with the first set of inconsistent low pressure readings I saw. Apparently, if there’s not enough refrigerant in the system, the compressor won’t kick on. The directions on the canister of refrigerant say to dump half of the can into the A/C system to jump start the compressor (note: many people online say ‘Dear God under no circumstances do that!’). That sounds like something I did and then started seeing more consistent evidence of the compressor running, so score one for that theory. Of course, that theory kind of falls apart when you remember that nice cold air was coming out of the vents before I did any of that and that pretty much means that the compressor was running. I suppose it’s a remote possibility that the refrigerant was very low and the compressor was running all the time to some effect but the levels were too low to get a consistent reading, but given my lack of experience in this area I’m pretty much pulling theories out of nowhere at this point.
  2. I didn’t seat the connector correctly the first time and essentially emptied a whole can of R134a into the atmosphere before I re-seated it and started seeing more consistent pressure readings OR I wasn’t paying attention and no refrigerant was coming out of the can on the first try. I think it’s possible I emptied the can into the air (sorry Mother Earth) but I’m not convinced because I think I would have noticed. It’s possible that no refrigerant was coming out, but the can did get pretty light after the first pass filling the system, so I don’t know what to think.

Of course, neither of those theories explains why the A/C completely failed to work on the short drive I took it on after filling the refrigerant. It’s possible that the drive was simply too short - it took a couple of minutes during the morning drive for the system to really kick on - but that’s troubling by itself: when I turn the A/C on it should be cold and cold pretty darn quick. Having to wait five minutes for cold air is a symptom of a problem - especially when it seems to kick on pretty quickly in other circumstances.

It’s also troubling that the system was still low on refrigerant in the morning. Low refrigerant means a leak. Luckily, the shop put a UV dye into the system so if there is a leak they can use a black light to find the source quickly.

The canister of refrigerant was $30 and the A/C service from the shop was $60. That’s not an awful cost considering that now my wife has a car with working A/C and if there is a leak we can find it quickly.

All in all, this is a win.

UPDATE:

So it seems this is less of a win, maybe something of a vindication?

After all of this, my wife was driving her car today and the A/C didn’t work. Then she drove it again and it did work. Definitely intermittent, very likely something preventing the compressor from running. My vindication is that I didn’t break it when I added refrigerant.

UPDATE… UPDATE:

The final word on this was that there was a refrigerant leak. When they recharged the A/C they used refrigerant with a dye in it so they could track any leaks with a blacklight. When it stopped working, we took it back in, they fixed the leak, recharged it and charged us nothing for it. It worked consistently after this to my wife’s satisfaction and I was glad I didn’t have to pay any more for a final fix.

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