DenLorsTools.com Summary: Motor vehicle air conditioning questions answered from all over the world by a master air conditioning technician in Florida. Simple to understand terms are used to resolve issues and to help the reader understand problems with their car’s Air con system (A/C system). Low gas (refrigerant) is the most common problem a car’s aircon system could have, but it’s not always the issue. One shouldn’t assume that the solution is always to top-up (top off) a system. A re-gas that adds too much R134A only causes more problems. Many garages will do a free pressure check. However, simply checking the pressure readings is not a foolproof test of the air conditioning system’s health. But, a knowledgeable motor vehicle technician can make a good evaluation of the A/C’s performance based on the readings and a visual inspection of the components. After evaluation, a ragas (recharge) may be done or a more accurate fill of refrigerant can be performed by removing the remaining refrigerant, vacuuming the system down and recharging with the vehicle’s specified amount of gas.

Question – The vehicle sat for 6 yrs but it was working when last used. It’s an R12 Freon system and the AC compressor turning but it wont take charge from my R12 can. Please help. Red.

Answer – Red, after the car has been sitting for 6 years the seals are likely to be dried up and will probably leak. Especially the front seal on the compressor. This doesn’t explain why the refrigerant won’t go in to begin with though. A little should go in without the compressor running. After some starts to go in, the front hub of the clutch should start to engage and disengage. This is called cycling. Since you are getting NO FREON to go out of the can at all, I’d say you are doing something incorrectly. If you are using a simple can tap, perhaps you’re not opening the piercing valve before trying to charge the system. Once you get refrigerant to go into the system, check for leaks, especially the front of the compressor. Good Luck.

Question – I am From India. I have Fiat Punto that is two years old. The issue is that when I am driving for long I see the ac blower pressure reduces after an hour or so. And when I switch the blower speed to 2 or the highest speed, after 2 mins the blower pressure volume comes back to normal. Other than that I am getting cold air but this issue has been present since I bought my car. The service guys at the garage have failed to rectify the issue. Can you help me in this? Yati.

Answer – Hello Yati. It’s possible that the evaporator is getting too cold on the low setting. The AC system on any car tends to get the coldest when on the lowest blower speed. When you switch the blower speed to a higher speed the ice melts and the air blows through the vents normally again. This would be difficult to duplicate for the guys at the garage, since the vehicle would need to be driven for a long period of time to get the problem to occur. Maybe you could suggest this possibility of the evaporator coils icing over, to the shop so they can make more of an effort to get the problem to occur. Good Luck.

Question – Topped the air con up on my Ford Fiesta. Was fine however when I revved the engine a little I noticed the compressor kept cutting in and out. Why is this? Cheers Dave.

Answer – Dave, It’s normal for some cycling to occur. But if it’s not cooling properly, it is also possible that it’s under or overcharged. I Â assist in diagnosing the problem without the high and low readings. The high pressure switch will turn the clutch coil off if the high side gets too high to protect the compressor from damage from excess pressure. The low side pressure switch will shut the coil power off also, because running the pump (compressor) with too little refrigerant can also cause damage. See our AC Gauge Readings Explained repair article for more insight. Cheers, Dennis.

Question – I have a 2006 Jaguar S-Type, with a 3.0 V6. I’m experiencing warm air from the AC vents after the engine is warm. It’s fairy cool when I first start up each morning. I had the Jaguar dealer replace the Climate Control Module (in the dash) in June of 2013 after having the exact same symptoms of warm air blowing from the vents. But of course to my luck, the $2,000 part/labor job went out of warranty June 4, 2014. I’m almost positive my AC is overcharged, as my readings show 55 on the low side (in the red) with the engine running and 98 with the engine off. My research says an overcharge situation can also affect the cooling. So should I take the car back to the dealership and pay $120 diagnostic fee for them to tell me what I already know and possible get the levels back in correct ranges or is there something I can do to bleed off the excess Freon? If the Control Module has gone bad again (after one year!!!) I certainly don’t want to shell out another $2,000 on this car. Any thoughts would be appreciated. Earnest.

Answer – Earnest, without knowing the high side reading, it’s not as easy to guess if it’s overcharged. If the high side readings are also too high, it could be overcharged. It’s also possible that there’s not enough air going through the condenser, or maybe the compressor isn’t pumping sufficiently etc. Whatever you do please don’t vent refrigerant into the atmosphere.

Follow-up from Earnest – Thanks for the response. If I can find my manifold gauges, I’ll be able to post a high and low side reading. Somewhere in garage. Still looking. And don’t worry, I will not vent the Freon into the air. Looks like a trip to the dealer with my checkbook is in the works.

Question – I have a 1999 Corolla re-charged system as directed and now the compressor keeps surging and air is not getting colder. I don’t know what is causing the surging. Please help.

Answer - Most likely over-charged. The compressor will shut off if the high side readings are too high (around 450-500 psi). Not knowing what the pressure readings were before adding Freon and now not knowing what the readings are after adding, makes diagnosing the problem anyone’s guess. Maybe it had a different problem to begin with other than low refrigerant. Adding Freon to an already full system causes more problems and can make the system actually blow warmer not colder. I just saw a commercial for a product called AC Pro sold at AutoZone. It’s a DIY Freon adding kit. The commercial shows a couple of guys adding refrigerant without any clue if low refrigerant was really the problem to begin with. It also has stop leak in it which can clog and restrict certain components in the car’s AC system and the repair shop’s expensive recycling equipment. I want to help people work on their systems the right way and when I see products like this marketed to the public as a safe easy fix for any AC problem it’s very frustrating. So my recommendation is to get the low and high side readings and see our AC Gauge Readings Explained article. Good Luck.