GM Complex Schematics - Complex Problems Figure 3: This dual cooling fan wiring schematic can qualify as a "maze" unless you take a few minutes to break it down by functions. Once you know how each circuit works, you can determine the circuit most likely to be causing a problem when one or both fans are inoperative. Not a week goes by where we don't get many requests coding circuits. See Figure 4. for help from technicians battling the same old enemy - Simplifying Automotive Electrical Wiring Diagrams / complex schematics. While the actual repair is often simple, diagnosing complex electrical / electronic systems is Schematics far from simple. The schematics and diagnostic trouble When tackling a problem with a radiator fan not turntrees that are supposed to help us quickly find solutions ing on when it should (or in some cases staying on when to problems often end up overwhelming us to the point it shouldn't) the first order of business is to determine the where we push them aside and "just try a part." following facts: In this MACS Service Report, we'll revisit the topic of 1. How many fans is the vehicle equipped with? wiring schematics with a fresh new example - electric fan 2. How many speeds are each fan supposed to run? motors. Whether you're diagnosing a newer vehicle with 3. What controls the relays which control the fans? a 3-phase brushless fan motor or an older one with a pair 4. How many combinations of ON / OFF / SPEEDS of simple 2-wire DC fan motors, schematic interpretaare there? tion can be difficult to say the least. I recently ran across In Figure 3 we can clearly see a pair of 2-wire cooling a schematic for a 2013 Chevy Malibu 2.4L with a pair fans labeled "Right" and "Left". Along with that we see of simple 2-wire DC radiator fan motors. The diagram three relays controlled by two ECM outputs. Short of a showed three relays and two PCM relay control circuits detailed and accurate "theory of operation" write up in (Figure 3). A quick look at what I presumed would be the vehicle's service manual (the likes of which are bean easy to understand 'road map' turned into a gaze of coming more scarce as time marches on), we can guess confusion staring at this 'maze' of wiring. I actually felt that since there are two fans there would be at least three a bit intimidated. Then I recalled the practical class Jorge combinations of operation: Menchu from AES Wave presented at a MACS conven1. Both fans off tion many years ago on simplifying schematics by color 2. Right fan on low speed / left fan off May 2020 2 MACS Service Reports