Welcome to Myths Busted by Brad

Do you get a lot of questions working in the automotive and heavy duty industries? Interesting ones? Tricky ones? Sometimes even silly ones? Some that tend to stick, but are they necessarily accurate or true?

Stay tuned for a series of myth-busting to help you explain the ins and outs of technical aspects relating to common myths when having  these conversations with your customers. When you deal with Highgate Air, we promise you will experience better, having the benefit of dealing with a team that get it. No question is too hard, too difficult or too obscure.

Haven’t we all heard of this on before?! “You need to make sure to turn off your air­­ conditioning before switching off the engine or the compressor will fail prematurely.” Below, we’ll dig a little deeper into that piece of advice and the reasoning behind it.


In short, no. With modern vehicles it is not necessary to turn your air conditioner off before turning your vehicle off. That being said, it doesn’t hurt to disable electrical systems, including the fan, before disengaging the ignition, but it’s not a necessity! Remember, now we have ECU (Electronic Control Units) that safely shut down elements as you turn the engine off.

But what prompted this myth and kept it alive for so long? A theory is, that the compressor would be damaged from the immediate turn-off or that the battery would be drained with the clutch still engaged! Reality is, as soon as the engine is turned off the current is cut to the compressor and the clutch disengages. With new technology and electric systems, the ECU controls shut down and avoids running the battery down.

For one, when engines were carburettor based and certain elements of the system weren’t as efficient as they are now, the compressor would place a significant load on the engine while the system was running and this resulted in the FICD (Fast Idle Control Device) to increase the revs of an engine when the A/C Compressor cuts in. In most modern vehicles this is now all controlled by the ECU and car control systems.

So, now this myth is busted, feel free to print this off, share on your social media, put in your waiting rooms or add to your own email to customers while staying tuned for the next in the Highgate “Myth-Busters” series.

Also, remember the back of the Highgate Catalogue and Tech Guide gives you a large amount of information for you to use when you are scratching your head for an answer to a difficult problem!


Have another myth you would love Brad to bust? Click here to share your myth!