Archive for May, 2015

Your Car is Lying to You! (But it’s OK)

Friday, May 15th, 2015
Airdrie Ford Repair

The oil pressure gauge in this 2005 Ford F-150 always reads exactly the same, regardless of what the actual pressure is.

By Chris Dekker


The technology being integrated into new vehicles is amazing, but sometimes takes some getting used to.

A great example of this was the integration of “smart” charging systems into late model Chevrolet and GMC trucks. To save fuel, the alternator can “shut off” during periods of low electrical demand, which reduces drag on the engine. During driving, it’s totally normal for the battery voltage to fluctuate anywhere between 10 and 17 volts –  a big difference from the days of old where 14 volts meant your alternator was charging properly, and 12 volts meant that it wasn’t.

This change had unexpected consequences: GM dealerships were flooded with customers who, after watching their battery voltage gauge, thought their trucks were experiencing an electrical failure – and GM wasn’t alone in this. Do you know what many car manufacturers did to fix the problem? They eliminated the gauge.

But this isn’t always a good solution. Truck buyers, in particular, are a traditional bunch; and they have grown accustomed to all of these different gauges (oil pressure, engine temperature, battery voltage, transmission temperature, etc) and the information they provide. Many won’t purchase a truck without these displays, which has lead to a new development in recent years: the introduction of gauges that “lie” to the driver.

Maybe “lie” is a little harsh. These gauges fib a bit. Many analog gauges in newer vehicles are programmed to show one reading all the time, as long as the reading they’re supposed to display falls within an acceptable range. Unfortunately, this means some vehicles are now filled with instruments that no longer display any real information at all. For example, the oil pressure gauge in a 2004+ Ford F-150 always displays exactly the same reading (about 2/3 up) as long as the engine is making any oil pressure at all – even if the pressure is less than the 25 PSI that Ford specifies as the bare minimum necessary. This is undoubtedly to avoid confusing customers, who may not understand how normal oil pressure starts off very high from a cold start, and drops sharply as the engine warms up. In fact, every gauge except the tachometer and the speedometer in the 2005 F-150 instrument cluster shown above is “dumbed down” to some degree.

This isn’t just a Ford thing; most car manufacturers are doing this. Most Volkswagen temperature gauges now read exactly in the middle, as long as the coolant temperature is between 65 and 110 degrees Celsius, to avoid worrying customers with normal changes in engine temperature. Other car makers have moved from an analog temperature gauge to a system of simple warning lights: a green light means the temperature is OK, and a red one means it’s too hot or too cold.

It’s easy to understand why car manufacturer’s have moved to these “idiot gauges” in an age where most car owners don’t even check their own oil any more. However, as someone who appreciates the information an accurate display can provide, it’s frustrating as well. If anything, this lack of real information for the driver further underscores the importance of having a qualified mechanic check over your vehicle regularly!