Seven years ago? Or, perhaps, eight? One of those big vans from USA came with a strange complaint. “Hot air from the AC vents in the passenger side when the vehicle takes a left turn”.

The vehicle spent almost one week with an AC technician before it went to a master technician. The AC technician has opened the dashboard, checked all the flaps and doors that control air flow expecting to find a loose door/flap that opened at times allowing hot air to the passenger side.

Some experienced troubleshooters say “If you know the problem 100%, you are already 90% into the solution”. I completely agree with this. Whenever there is a wrong diagnosis, whenever there is a delay in diagnosis, the culprit will be lack of clear understanding of the problem.

The master technician was one of those ideal guys I would ever like to have in my team.  He is from that part of the society where higher education is still a luxury and as every one else in his family he also started working at a very early age. When I met him he was already seven years into automotive electricals and already an expert in his field. Lack of proper education was the only handicap though by hardwork and dedication to his job he had almost overcome it.What made him different and so valuable was the way he approached a problem.

“If you know the problem 100%, you are already 90% into the solution”. He was a staunch believer of this. He will not touch his tool box till the problem is 100% clear to him.

He took the vehicle at 8 am in the morning. By 11 am he was in my room with a very vital information which no one noticed in the last one week. He has almost solved the problem, but sadly, could not explain what exactly was happening.

“Teacher” , he used to call me teacher as I was a technical trainer also, “this is it”. “It” was a small glass bottle of car perfume, the wick type with a small handle like thing to fix it. “When I remove this, there is no problem. When I fix this, the problem starts. I will very soon go crazy if I can’t find out why it is happening like this. My poor brain is burning…help me”

Soon we were on the road. True, with the bottle in place, when the car takes a left turn, there was hot air from the passenger side vents. When the bottle is removed, there is no problem.

The air conditioning system in this model was totally new to us. First ever air conditioning system complaint we received in this model. Dual zone automatic with occupant body temperature sensing. In older models, the temperatures at driver side and passenger side could be separately set and controlled. In this model they have gone one step further. Two infrared temperature sensors monitor the occupants body temperature and control accordingly. We could find two small black projections near the air conditioning centre vent directed towards the driver seat and passenger seat. Those were the infrared temperature sensors.

The driver has fixed the perfume bottle in the centre vent, between the two infrared sensors. The liquid level was just below the infrared sensors.When the vehicle took a left turn, the liquid in the bottle moved to the right side, inertia, and came in front of the passenger side sensor. The control module took the sensor reading, which was the liquid’s temperature, as the passenger’s body temperature and controlled the air mix door actuator at the passenger side to increase the temperature.

Why the problem was not coming on right turns? Here it is left hand drive and you get only left turns at round abouts. Right turns are very rare. And this will not happen at slow speeds. We verified this in a ground nearby. We took right turns at speeds sufficient to cause the liquid to rise. The liquid moved to left covering the infrared sensor at the driver side and soon there was hot air blowing from driver side.

We advised the customer to fix the bottle at some other location and never heard from him again!

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