ACTION NAPA AUTO Parts - (Page 6)

Engine cooling systems: Electric cooling fan operating strategies This energy savings is one of the main reasons why even many rear wheel drive (RWD) vehicles now use electric cooling fans. In most cases, they do not operate until necessary, when the engine coolant temperature climbs above a certain point. This reduces the overall load on the electrical system during most driving conditions. Continental VDO Back in the day... A typical dual fan setup -The engine cooling fan keeps the engine operating temperature at a controlled level to allow and maintain a constant temperature over a variety of driving conditions. MACS Continental VDO In the early days of electric fans, control and operation were pretty simple. The '83 Cavalier, for example, only had one electric fan controlled by one relay. A fuse supplied power to the relay's coil, the other side of which was connected to a switch mounted in a coolant passage. This engine grounded Coolant Fan Switch would close when coolant temperature reached 238°F, energizing the coil. On the switch side of the relay, the body-grounded fan motor's power circuit would be completed through a fusible link. The only modiﬁcation to the circuit was for vehicles equipped with air conditioning, which was optional at that time. In that case, the cooling fan would be turned on whenever the dash control was set to one of the A/C positions. The early 90's V-6 Ford Mustang and Taurus / Mercury Sable also had only one radiator fan, which was PCM controlled through the Constant Control Relay Module (CCRM). The fan was turned on whenever engine coolant temperature reached 221°F and turned off The 1995 Ford Taurus used only a single electric cooling fan. The shroud was molded to guide air passing through the heat exchangers. at 200°F, but was always on during A/C operation (did not cycle with the compressor clutch). The exception was when cruising at speeds over 43 mph, when ram air provided the necessary air ﬂow. More modern times... In later years, OEMs began using two fans, running them at two speeds. In many cases, placing two fans side by side is required simply because of the narrow, rectangular shape of modern radiators. The geometry is such that one fan alone cannot provide adequate air ﬂow across the entire surface area, even with molded shrouds. Here is an example from a 2006 Chevrolet Malibu with a 3.5-litre V-6 engine. This vehicle's cooling fan system uses two electric fans which are turned on and off by three fan relays, arranged in a series/parallel conﬁguration. This allows the engine control module to operate each fan at both high and low speeds. 6 ACTION/NAPA * Spring 2015 Individual fan motors can still be ordered separately, although complete fan assemblies are stocked more often. Many consider them to be more "technician friendly" since they're easier to replace. There are several parameters for when the PCM will engage the fans at low speed, but under normal circumstances this happens when engine coolant temperature reaches 223°F or when A/C pressure exceeds 190 psi. Otherwise, the fans are not turned on. However, if ambient temperatures exceed 122°F, the fans will remain on during A/C operation. High speed operation kicks in when coolant temperatures reach 230°F, A/C pressure exceeds 240 psi or if certain DTCs are set. A typical electric engine cooling fan system is composed of an electric motor, a relay, a fan blade, a fan shroud and a thermostatic temperature control switch. Most front-wheel drive cars have electric engine cooling fans because the engine is usually mounted transversely, meaning the output of the engine points toward the side of the car. The fans are controlled either with a thermostatic switch located in one of the coolant passages or by the engine computer, and they turn on when the temperature of the coolant goes above a set point. They turn the fan off when the temperature drops below that point.

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