Question: I have a 1997 Chevy Blazer with the 4.3-liter V-6, automatic transmission, and four-wheel drive. The 4WD system won’t engage. When I push the 4-Hi button, the light flashes and then goes back to 2-Hi. I originally found the fuse to the 4WD system was blown, so I replaced the fuse and that seemed to work. However, the last time I tried to put the truck in 4WD, the 4-Hi light flashed and went back to 2-Hi. I checked the fuse and it was blown again. Is it possible that the engaging motor might be pulling too much current and blowing the fuse?
Answer: You’re in the ballpark suspecting the motor. When the 4-Hi switch is applied, a connection from the 4WD fuse is completed to the transfer-case control module. The voltage then goes to the motor/encoder assembly at the transfer case. It gets a bit complicated, so you need the repair manual information (including resistance checks for the motor/encoder assembly) in front of you to accurately test the circuits. If motor resistance is below spec (low resistance/high current draw), that may be the cause. But the short could also be coming from other areas, such as wiring insulation being rubbed through and shorting out on the chassis. I haven’t found a common cause of the 4WD fuse burning out on this platform Blazer, and there are no relevant technical service bulletins, so either get the auto repair manual information and roll up your sleeves, or get it to a technician who can track down the circuit overload.
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