It’s summertime and everybody is writing into auto forums asking how to fix their A/C systems. And the answers people post are always the same—recharge it with a do it yourself )DIY) kit from the auto parts store, or (from professional shop owners) DON’T touch it because it’s not a DIY job. The real answer is this; if you want to fix your own A/C, you either need to invest in some equipment or take a chance with a recharge kit. If you try the kit, you may find that all the new refrigerant leaks out and then you’ll be out the $40 and still have to pay a shop to fix it. Not all leaks are created equal. For example, if you live in the cold North Country, it’s really common for seals and connectors to leak a small amount of refrigerant in the winter, The components get really cold and contract and poof, there’s goes some of your refrigerant. Next cooling season your A/C either blows warm air or barely chilled air because it’s low on refrigerant. However, if you take it to a shop in the summer when the connectors have expanded and resealed, it’s almost impossible to find the leak.

In this kind of case you may be better off recharging it in the spring rather than spend a small fortune paying a shop to find the mysterious leak. That’s where these do it yourself recharging kits come in real handy–for small leaks that are hard to trace. But be warned, they don’t work if you’ve got a large leak that isn’t caused by cold weather expansion.fujitsu air conditioning heating units But let’s not kid each other, there’s no guarantee a DIY kit will work. window unit ac compressor wont stay onFirst off, unless you have a professional gage set, you really don’t know how much refrigerant leaked out. sanyo air conditioner window unitThe system could be completely empty, in which case the leak MUST be repaired and the system evacuated by a vacuum pump before you refill it.

If you refill it with air already inside the system and it’ll never cool properly. Worse yet, the moisture in the air will form acids that destroy your compressor, evaporator, and condenser. So you end up with a system that’s totally destroyed. The part most DIYers miss is that you should set the system to MAX A?C and turn the blower motor its highest speed first. Then start adding refrigerant. If you read the directions on the DIY recharging kit can, it’ll tell you to charge the system a bit until you see the A/C compressor clutch spinning. That’s great, but what if you’ve emptied the entire can (about $40) and it still isn’t turning. Yeah, that’s right, you just wasted $40. On the other hand, if the compressor clutch does start spinning, that’s a sign that the system has enough pressure to override the low pressure cut-off switch. You can continue to fill the system until the recharge kit gage reads the recommend pressure. But you MUST avoid this common DIY mistake.

More is NOT better. The charging window on R-134a refrigerant is 2-3 OUNCES. Overcharge the system and you actually REDUCE cooling. Stop when the gauge reads the right pressure. Now, if the clutch doesn’t engage, that doesn’t automatically mean the system is empty or low on charge. It could mean that the magnetic clutch coil has failed. The coil creates a magnetic field that pulls the clutch plate into the pulley and that’s what operates the compressor. So if the coil bites the dust the compressor will never engage. You can test a clutch coil yourself. First, remove the electrical connector going to the coil. Using a digital multi-meter set on ohms, touch the two leads to the electrical contacts on the coil. You should get a continuity reading. If so, keep one lead on the electrical contact and the other on any metal part of the compressor. If you still get continuity, the coil is shorted to ground. Repeat the test using the other electrical contact on the coil. Got continuity but no short?

Great, that usually means the coil is good. What we don’t know is if it’s getting power from your vehicle. This is where it gets tricky. In the old days the A/C system would automatically power up the clutch coil any time the A/C was turned on and the key turned to the RUN position. But in late model cars, the computer wants to see idle RPMs at a certain level before it’ll power on the compressor clutch. So you may have to jury rig longer leads to your meter so you can move it out of the way and start the engine. This can be dangerous, so do it at your own risk. Tip #1 You can replace all the parts in your A/C system yourself for about $800That $2,500 quote you got from the shop—well if you just invest in some tools, you can redo the whole system AND own the tools for under $1,000. And you’ll be set for repairs on your friend’s cars too. Tip #2 Get a vacuum pump Everyone is afraid of using a vacuum pump. There’re not that expensive. Find one here for under $100.

If you have to replace parts in your A/C system, you MUST pull a vacuum for at least one hour after you’ve put it back together. You can OWN a pump for less that you’ll pay a shop. Tip #3 Get a manifold gauge set No pro ever refills the system through the low pressure port. They use a manifold gauge and connector the red hose connector to the high pressure port. They connect the yellow supply hose to a side can tap (see tools below). Then they charge the system with the liquid in the can. It goes much faster than using vapor charging. Bad Idea #1 Hotwire the low pressure cutoff switch Some people think they can place a jumper across the low pressure cutoff switch to hotwire the compressor so it spins while charging. This is a really BAD idea. If the system is empty, that hotwire job will start up the compressor DRY. Pretty soon you’ll have a molten mass of what used to be your compressor. You can add refrigerant to the system even if the compressor isn’t running.

It’ll take MUCH longer, but it’ll protect the compressor. So forget the hotwire job and fill the system one-half can at a time. Then try starting the engine to see if it kicks in. Bad Idea #2 Keep charging after the recommended pressure is reached. This is a repeat of what I said above. Just click on the link below to pull up a charging pressure/temp chart for R-134 refrigerant. Bad Idea #3 Recharge every few weeks so you don’t have to fix the system Every time the system loses refrigerant, it also loses oil. Lose enough oil and you’ll find up with Black Death. That’s what happens when a compressor starts to self destruct. The metal starts wearing away, mixes with the refrigerant to form a black muck and gets deposited throughout the system. If your system dies from black death and you just replace the compressor, you’ll be replacing the compressor again in a year. You must flush the entire system with a professional flushing kit, and even then you probably won’t get all the black muck out.

The only safe way to come back from black death is to replace the entire system. See how much trouble you can get into with those DIY recharging kits? If you want to kill your A/C system, go ahead and refill it with another type of refrigerant. I guarantee you it’ll be dead within a year. Different refrigerants do NOT mix. Bad Idea #5 Adding the wrong oil Each car maker recommends a particular oil and certain viscosity for their system. There is no One Size Fits All oil. Add the wrong one, and, you guessed, it—compressor failure. Bad Idea #6 Add refrigerant to a Hybrid vehicle The compressors in many hybrid vehicles are driven by electric motors. The coil windings of the motors are cooled by the flow of refrigerant and a non-conductive oil. If you add a DIY can of refrigerant that contains oil (and most of these kits do), you could wind up dead, as in, no longer breathing. I’m not kidding here. This is a job for a pro. Find this article useful? Posted on June 29, 2012 by Rick Muscoplat