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.

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DenLorsTools.com Summary: Questions answered by a master tech, regarding a car’s AC system when the Freon just won’t leave the can. When the vehicle’s air conditioning system doesn’t accept a charge of refrigerant there can be many issues, or the problem could be solved easily. Understanding how the system works in easy to understand terms is the best place to start. This and other helpful A/C articles when it’s hot outside and it’s time to get the car’s air con working again.

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DenLorsTools.com Summary: So what’s the best refrigerant leak detector to use when looking for leaks on car air conditioning systems? I’ll answer that but first a little quick history. I originally used a propane leak detector when I started working on air conditioning on cars back at Goodyear in the 1980’s. The old propane leak detectors were very dependable. No false alarms. When Freon burns the flame turns a green and with very large leaks it turns into a bright purple. Problem is with burning Freon, toxic fumes are produced. It’s called Phosgene Gas. Very poisonous. I learned quickly that you don’t want to get a whiff of that. Obviously the propane leak detector was discontinued because of obvious reasons. As a side note. Refrigerant sucked up from the cars intake can burn in the engine and spew out Phosgene also. Once while working in an enclosed shop at CarMax, a tech working next to me had a huge Freon leak while the car was running. The Freon was immediately burned and spit out the exhaust. Not a pleasant thing to be around. Anyway, the point is; if you ever have a large refrigerant leak while working on a vehicle, make sure the engine is off until the area can be ventilated.

Refrigerant Leak Detectors

Refrigerant leak detectors need at least 50 psi of Freon in a system to be able to work. After-all they detect Freon and if there’s not enough in a system to leak out, how could it work? And check the system with a good electronic leak detector. I recommend that you don’t trust a leak detector every time it beeps, even with a good one. I’ve used leak detectors that would go off when sniffing an oak leaf, anti-freeze from the engine’s cooling system and even my breath! The best electronic leak detector that I’ve ever used was a Yokogawa/Bacharach. They are not cheap, but anyone doing a lot of AC work knows how expensive and time consuming it can be to misdiagnose leaks. So it’s important to have the best one you can afford. I first learned about the Yokogawa brand years ago (while working at CarMax) when I read a TSB (Technical Service Bulletin) from Nissan which named it as their only authorized leak detector for their warranty work. That’s when I purchased one. I paid way too much to the Snap On guy that had to special order it. He probably doubled his money on me. That’s a common practice for tool truck guys… That was way before I considered selling tools myself. No false alarms ever with my Yokogawa. We sell other brands but if anyone ever asks I always recommend the Yokogawa (also known as Bacharach).

 World’s Best Freon Leak Detector

So the Yokogawa leak detector that I purchased looked a little like an electronic device used in NASA from the 60’s or 70’s. It was made with metal and was stored in a vinyl case; an almost leather looking pouch. They look basically the same today. It plugged into an electrical outlet instead of running on batteries. While this makes it a little less convenient to use, it helps it to be more dependable because the power supply is constant. It also had to warm up before using it. But the greatest thing about it was- it never gave me a false alarm. If it alarmed, there was a leak. That’s saying a lot. It also works on all types of refrigerant including R12 and 134A. The TIF models that I had used prior to this always gave plenty of false alarms. The TIF and other battery operated leak detectors that I used, also tended to be even less dependable as the batteries faded.  So in my book, the best leak detector in the world is the H10 Yokogawa. See the AC Leak Detection Tools section.

Foggy car windshields are a real safety issue. Foggy windows make it hard to see out and therefore dangerous to drive. Particularly when it’s raining and the car windows have to be rolled up this can be a huge problem. The problem can be even worse if the haze on the windows has a filmy consistency preventing the view to be clear even after wiping the windows off. If there is a filmy residue it could be a sign that the heater core is leaking.

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Charging up a car’s A/C system by adding 134A will make it blow cold, won’t it? Sometimes is the correct answer. With some luck this might be just the ticket. But without knowing the gauge readings, topping off a system is just a guess. One of the most common causes of a car’s A/C not cooling is low refrigerant so there is actually a good chance that adding refrigerant is needed.

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Image above courtesy of Mastercool

©DenLorsTools.com Summary: This article has an excerpt from the Mastercool 69788-A pdf manual that outlines installing the replacement filters. Replacing the Dryer Filters is now necessary to meet the SAE J-2788 requirements for adequate moisture and contaminant removal. Keep in mind this is not something that the AC machine manufacturers are requiring, it is required to comply with the SAE J-2788 mandate. That’s why all the machines no matter which brand that are SAE J-2788 compliant, which includes all of them manufactured now, will require the replacement of filters every 150 pounds recycled. A code is required that helps ensure that the filters were actually replaced.

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© DenLorsTools.com Summary:  There are several things that can cause a bad odor inside the car. Spilled drinks can be an obvious source of a bad smell. Or, remnants of fast-food that has fallen to rest, in the infamous “black hole”. That’s the area between the console and the seat that dropped crumbs seem to be drawn to. With lack of cleanliness aside, there are less obvious causes of stale odors that come deep, from within the dash.

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Black vehicles never cool as easily as white ones, consider this on your next purchase.

© DenLorsTools.com Summary: ASE Florida Master auto technician answers questions from a reader in Pakistan. Pakistan’s temperatures exceed Florida’s which is normally considered one of the most demanding climates on a car’s AC system. Read on for several questions from Usman in Pakistan.

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© DenLorsTools.com Summary: Florida ASE Master Tech explains what automotive AC vacuum pumps are used for and answers frequently asked questions regarding their practical use when servicing car air conditioning.

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© DenLorsTools.com Summary: Suggestions of possible causes, when a car air conditioning system stops cooling after a few minutes. Reasons why the A/C can stop intermittently.

There are several possible causes of a vehicle’s air conditioning system to stop working after being on for only a few minutes. Basically the causes are either the A/C evaporator is getting too cold and icing up or there’s an electrical problem causing an open circuit.

My Parents Chevy Had this Problem

Long before I knew anything about A/C. When I was about sixteen or seventeen years old my family took a trip from Florida to Virginia. We drove my mother’s fairly new (at the time) 1980 Chevrolet Citation. It was actually considered an 80 and 1/2 because it came out so late in the year. Dad had purchased it because it was… well – cheap. It was one of Chevrolet’s first FWD (Front Wheel Drive) cars. It had a manual transmission and no air conditioning. Living in Florida, Dad soon realized Mom would benefit from having an aftermarket AC system installed. The AC worked great on the short trips Mom took to the store and to work. But, when we left for the 1,000 mile trip to see my relatives it was a different story.

The air would blow very cold for a few minutes, Then it would blow regular non-cooled air. If we turned the AC off for a few minutes it would again blow ice cubes out of the vents for a few minutes. We stopped several times to have the AC looked at. The service stations ALL did the same thing. An evacuate and recharge. Meaning they would take the refrigerant out, pull the system down into a vacuum and recharge or fill the system back up. The AC would cool great. Dad would pay and we would get back on the road with hopes that this time it would be fixed. It never was!

Why “evacuate and recharge” for this problem?

I didn’t understand why an evacuate and recharge might fix the AC. Now I do. If there is moisture inside the AC system it can freeze when the temperature gets low enough. Refrigerant has a much colder freezing point when compared to water/moisture. If the evaporator freezes up, the water that’s normally on the outside of the evaporator will freeze. The sheet of ice that forms will prevent air flow or at least reduces it. Without air flowing through the evaporator fins, the heat/cool exchange cannot take place.

That was the reasoning for the service stations doing an evacuate and recharge on my Mother’s Chevy Citation. When the system is being held in a state of vacuum, the moisture is removed. The boiling point under vacuum is at a much lower temp, allowing the moisture to boil off and be sucked out of the system. Therefore, if the freezing up of the evaporator is caused by moisture in the system, an evacuate and recharge may fix the problem. Keep in mind that there is also desiccant in the dryer that also absorbs moisture from the system. If dryer is more than a few years old or the system has been “opened” theoretically the drier should be changed because the desiccant may be saturated with moisture and no longer able to remove moisture from the system.

What about a bad expansion valve?

Since the Evacuate and Recharge NEVER fixed the problem we had in the Chevrolet, the most likely cause of the problem was a bad expansion valve. Since it was an aftermarket AC system, the expansion valve may have have even had it’s probe incorrectly positioned. In either case the expansion valve allowed the low side pressure to get too low. Lower refrigerant pressures equals colder temperatures. If the expansion valve allowed the evaporator to get too cold the condensation on the outside of the evaporator can freeze up, forming a sheet of ice and stop proper airflow through the evaporator coils and fins. That’s why turning the AC off for a few minutes would help return things to normal temporarily. Allowing the ice to melt would remove the air blockage until the system ran long enough to freeze the water on the evaporator again which would repeat the problem all over again. Most expansion valves today have no external probe and no adjustment. So if this problem occurs it’s most likely a faulty expansion valve.

Compressor not engaging? The AC compressor’s electromagnetic coil for the clutch could be going bad.

The AC compressor is engaged (turned on) by a clutch. The clutch consists of a plate, a hub and a coil. If the coil becomes weak, it may not have enough power from the electro-magnet to pull the clutch plate into the hub. Another possibility is that the air gap between the plate and the hub has increased too much due to wear. If the gap is too big the magnet will not be capable of pulling the plate, engaging it with the hub. If the plate and hub are not worn too badly, sometimes just the gap can be reduced by using a smaller shim (looks like a washer).

A bad coil can sometimes be detected by checking to see if the clutch plate is engaged when the AC problem is occurring. If the plate (disc) is not turning it’s NOT engaged. If power and ground are supplied to the coil (and it’s not engaged and turning) the coil most likely is weak or has an open circuit within.

No power at the coil? 

No power at the coil could mean anything between the switch and coil could have a problem. I’ve seen broken wires, bad control modules, faulty switches, relays etc. This diagnosis most likely means an auto repair manual is required with wiring diagrams and system component locators. That is unless you get lucky and find a wire that is damaged by doing a visual inspection.

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