Tech feature: Honda aircon how-to

Diagnosing and fixing the aircon on a 2003 Honda Civic

FINDING THE FAULT IS NICE BUT FINDING OUT HOW TO FIX THE FAULT IS EVEN BETTER

Tried and tested techniques provide comfort but in this article Brendan Steckler shows how more sophisticated tools and testing techniques can raise the game.

This quest started with a customer calling to complain that his Honda’s aircon system was not performing well. Apparently it ran wonderfully when it was working but at other times it wouldn’t work at all, which puts it in a different category from the usual weak performance.

Joe drives an immaculately maintained 2003 Honda Civic. It had an astonishing 400,000-plus km on the odometer, and the vehicle was still going strong. Joe was keen to keep the vehicle on the road and the aircon working properly, so I agreed to check it out.

According to Joe, the aircon blows ice cold at times but at some point each day, it simply fails. A few hours later, it will be working again. This process seems to repeat itself each day.

Imagine for a moment a list of 30 potential failures that could cause a specific symptom. Now imagine having to test every one of those components to prove their functionality. Obviously this would take a long time.

Now, what can we ask the customer that could cut that list of 30 in half? What if we could then ask a subsequent question that could reduce that list of remaining potential failures by half again? How much more effective would our actual applied diagnostic time be?

It all starts with having enough knowledge about the functionality of a particular system (and the components that make up that system) to create a bird’s-eye view or mental image of that system. If we have that in-depth knowledge, we can visualise what the symptoms may be if each key component was not functioning properly. All of this leads to effectively applied analyses and rapid, accurate diagnostics. Here are a few of the questions I asked Joe and his answers:

Q: So the aircon does blow cold air at times?

A: Yes, it blows cold every morning, at my lunch break, and every evening leaving work.

Q: Does the blower stop at all?

A: No, air always comes from the vent — it’s just warm air.

Q: During the failure, do you get any warning lights?

A: No, nothing unusual seems to occur — just the hot air blowing from the vents.

Q: Are there any notable noises/squealing heard during the failure?

A: No, the car seems to operate the same with no strange sounds.

Q: Is there a specific time/place the symptom is exhibited?

A: Yes, it always seems to fail after I stop for coffee in the morning.

A 2003 Honda Civic

Building a mental picture of the main components and their functions

A mental picture of Ohm’s law

Hopefully you can see that each question helps rule out some possibilities and helps to focus my diagnostic approach before I even sit in the vehicle.

The first answer tells me that the vehicle must have refrigerant in the system. It also tells me that the compressor clutch engages, the drive belt is affixed, and the heat can be exchanged from within the cabin and at the front of the engine compartment. The second answered question tells me that I don’t have to invest any time in the blower circuit, as it always continues to push air, whether the symptom is present or not. The fact that no indicators are flashing leads me to believe the vehicle’s onboard computers don’t recognise a fault exists, and the fact that there is no squealing noise deters me from thinking the compressor belt may be slipping. However, it’s Joe’s answer to the final question that caught my attention.

THE TELLING COMMENT

I asked Joe to elaborate a bit further on his last answer. He said he has a 15-minute drive to a local gas station. Here, he stops each morning to get a cup of coffee. It’s when he gets back in that he almost always notices the aircon has given up and he is in for a hot commute to work. He goes on to say that if he goes out at lunchtime or when driving home, the aircon works flawlessly.

There is a clue there that I’m hoping you are pickingup on. The first thought that comes to mind for me is ‘heat’.

With the initial morning start of the engine, it has 15 minutes of drive time to come to operating temperature. It’s when Joe stops for coffee that the under-bonnet temperature begins to soar.

It’s time to recall Ohm’s law. Georg Ohm taught us all that there is a relationship between resistance, voltage, and current flow or amperage. We should remember that if resistance increases, it opposes current flow, and therefore the current flow will reduce. Keep in mind that if the temperature of a component increases, so too does the resistance. So, it’s only logical to recognise that as the temperature under the hood increases the electrical circuits will all have a reduction in current flow — it’s just physics!

ROAD TEST OR SCOPE?

As I initially approached the vehicle, I had a choice to make. I was either going to go on a 15-minute road test, return to the shop and allow the vehicle to hot soak (just as Joe experienced the symptom) before I attempted testing. This would likely be a wise decision, as reproducing the customer’s concern is almost always the first step in the troubleshooting process. The other choice would have been to pull the vehicle into the shop and analyse some data from the aircon system as it appeared to function normally. I decided to go with the latter, as I was curious to compare the differences between the system functioning normally and when it faulted.

We all know there is more than one way to come to a diagnosis on a vehicle. Although my approach changes depending on factors like vehicle configuration, available tooling, and circuit access, my goal is always the same: the most efficient approach to the fault. At the moment, the aircon system is engaged and performing well. There is not a fault present in the related circuitry of the aircon compressor clutch field coil, but I still chose to evaluate its performance using a current probe and a lab scope. The lab scope offers me the power of a DVOM (digital volt/ohm meter), but it offers a bit more. For instance, it allows me to see the change in the circuit operation over some time, whereas a DVOM only allows me to see circuit activity at a moment in time. The lab scope also offers a visual representation of electricity. This means I’m allowed to see the circuit perform the work it was designed to do but will also allow me to see when a failure occurs and the nature of the failure.

The current probe (or amp probe) is quite

Trying to connect to the circuit with a DVOM can be difficult and time consuming

The large compressor gap which triggered the fault after heat soaking

This set-up with a current probe and lab scope is much more efficient

It’s easy to see the pintle bump is delayed by the large gap in the compressor clutch

handy, as it can deliver information by simply clamping around the outside of a wire in a circuit. As the electrical current travels through the wire, a magnetic field is created. This magnetic field grows stronger with an increase in current flow. When coupled to a lab scope, the current probe trace can show us not only electrical current flow, but also the physical movement of inductive devices like solenoids. When a ferrous metal is moved through a magnetic field (like within a solenoid), a disruption in current flow occurs. If we see that disruption, it’s indicative that the solenoid shuttled. Yes, we can see physical movement with a current probe. It’s this knowledge I will lean on as I capture and analyse the current trace from the aircon compressor. After all, it is nothing more than a large solenoid.

I want to explain why I chose to monitor current flow to evaluate the aircon compressor clutch circuit. Current is the same anywhere in a series circuit. With that being stated, it’s quite a task to place the vehicle in the air and test the aircon compressor clutch circuit for available voltage, voltage drop, or even continuity. The amp probe will offer similar information. For instance, if the current flow is what’s expected, there simply cannot be any open circuits, excessive resistance, or voltage drop anywhere within the circuit — Ohm’s law taught us that, too. Furthermore, if the current flow was less than expected, it would now be justified to investigate the circuit a little deeper. We would be sure to find our fault as we pursued further using a DVOM but without any wasted time.

TELLTALE SIGNS

Reminding you that current is the same anywhere in a series circuit, I chose to monitor current at the under-hood fuse box because it was so easily accessible. By requesting the compressor clutch ‘on’, I captured the current ramp of the aircon compressor clutch field coil. At about three amps, it revealed that the circuit was indeed healthy, but something much more interesting was revealed as well. A ‘pintle bump’ is the visual indicator that demonstrates physical movement or shuttling of the compressor clutch. The circuit is engineered so that the bump will occur approximately 50-60 percent of the way up the current ramp. Although this aircon compressor clutch is operating properly at this time, it can be seen that the bump is occurring very late. If there was a reduction in current flow, there would certainly be a reduction in a magnetic field, and one may anticipate a late pintle bump (shuttling of the clutch) as a result. However, there is no reduction in current flow. So, a question comes to mind: what factor other than magnetic field can affect the engagement of the compressor clutch? You guessed it — the air gap.

Although the aircon compressor clutch has not failed to engage as of yet, the data in the current ramp directed my attention to the air gap of the compressor clutch. According to specification, the gap should be no more than .026”. The measured air gap across the aircon compressor clutch was almost double that distance!

PRYBAR TO THE RESCUE

I decided to prove my case and point before approaching the customer. I took the vehicle on the road to generate some heat energy. I allowed the vehicle to sit for 10 minutes and repeated my test. What I found (although not displayed here) confirmed my hypothesis.

The added heat from the road test/hot soak indeed reduced current flow due to the increase in resistance. Of course, this reduced the amount of magnetism generated by the energised clutch field coil. As a result, the excessive air gap didn’t allow the clutch to engage. There was not enough magnetism to overcome the large air gap.

A minor bump/coaxing with the end of my prybar allowed the magnetic field to draw the compressor clutch closed, and the aircon system functioned and performed well. Again, there was nothing wrong with the magnetic field, just too large a gap to overcome.

Growing your skillset is never promised to be easy and can more often than not force us outside of our comfort zone. That’s how you know you are striving to better yourself. No one is going to force you to be more efficient, especially if you are already diagnosing and repairing vehicles correctly. But I can promise you three things if you do: a strong sense of pride, reduced stress at work, and a much better understanding of how components function as a system to accomplish a task.

6-9AM WEEKDAYS

hauraki.co.nz

European car parc shock news: Sachs is number one

EVERY YEAR, MORE THAN 10 MILLION NEW CARS ROLL OFF THE ASSEMBLY LINE FITTED WITH SACHS SHOCK ABSORBERS — PROOF OF THE TRUST AUTOMOTIVE MANUFACTURERS WORLDWIDE HAVE IN THESE PRODUCTS

Sachs shock absorbers are distinguished by their original equipment quality and innovative technology, and are now ranked the number one shock absorber in European car parc coverage.

Sachs shock absorbers, a ZF Aftermarket brand, have refined the blend of comfort and performance to offer some of the world’s most demanding OEMs road grip and cornering behaviour that can be relied on no matter what challenges the road may present.

Locally, the Sachs range has more than 3000 shock absorber references, with a combination of mono-tube and twin-tube gas pressurised shock technology throughout the entire range.

Additionally, over 385 strut mounts and bearings, and more than 220 bump stop and boot kits are available.

There is also a range of Sachs shock absorbers for four-wheel-drives, off-road, and utility vehicles, known as Sachs Max.

Sachs Max shock absorbers support vehicles with up to a two-inch lift, with larger pistons and an increased bore size resulting in shock absorbers that are more durable, while continuing to offer the ultimate in safety.

Sachs also produces clutch components and its clutch catalogue numbers over 1500 items, including clutch covers and discs, flywheels, and clutch release systems. Clutch replacement kits for passenger cars provide all the relevant components, including pressure plates, disc and release bearings, up to and including special assembly grease.

For more information on the Sachs range available from ZF in New Zealand, visit: www. aftermarket.zf.com/au or call + 61 2 9679 5555.

Bendix launches environmentally friendly EV-Hybrid brake pads

BENDIX RAMPS UP THE PRODUCTS’ GREEN CREDENTIALS FOR ENVIRONMENT-CONSCIOUS EV AND HYBRID OWNERS

Australian innovator and technology leader in braking systems, Bendix, is launching a range of brake pads to meet the growing demand for EV and hybrid vehicles in Australasia. The new Bendix EV-Hybrid brake pads are cleaner and greener for the environment.

Made from organic materials for minimal environmental impact, the new EV-Hybrid brake pads have been specifically designed in the Bendix Ballarat R&D department. The new pads ensure a low environmental impact while ensuring low dust and noise levels. This new Bendix development ensures low particle emissions when braking resulting in cleaner wheels, and longer disc brake rotor life.

The new brake pads have been specifically formulated for electric and hybrid vehicles, which, because of the absence of background engine noise, demand quiet braking and low noise. Bendix expects to announce expanded vehicle range availability before year’s end.

The Bendix EV-Hybrid brake pads are made from copper-free organic brake friction materials and are certified to the Automotive Aftermarket Suppliers Association (AASA) ‘N’ rating. This rating confirms the Bendix EV-Hybrid brake pads contain less than 0.5 percent of copper by weight and permits Bendix to use the AASA LeafMark ‘N’ icon.

“The AASA LeafMark represents one of the highest global environmental standards for brake friction manufacturers and the Bendix EV Hybrid material has been tested and accredited by an independent, third-party lab and certified to meet this high standard,” says Bendix product manager Ian Campbell.

“Bendix has decided to go down this path to further its credentials as an environmentally conscious company.”

The brake pads packaging come in FSC Certified packaging which means at least 70 percent of this packaging comes from FSC certified or recycled material, while 30 percent is made from controlled wood. “This is also helping to minimise impact to the environment, and is 100 percent kerbside recyclable,” Ian says.

The EV-Hybrid brake pads incorporate the Bendix green titanium stripe for instant friction without the need for bedding in the brakes on installation, saving both time and money for both the installer and the customer.

For more information free call the Bendix Brake Advice Centre on +61 3 5327 0211, e-mail brakeadvicecentre@bendix.com.au, or see www.bendix.com.au.

parts@1stparts.co.nz

(09) 638 6439

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