Fuse 27 contantly blows
I am troubleshooting a blown fuse issue on my 1998 Ford Ranger XLT 4x4 Automatic.
At the moment, if I insert a fuse and turn the ignition to "ON", the fuse blows immediately. Obviously an over-current situation.
According to the manual, this fuse controls the following:
Electric Shift (I understand this to be part of the 4x4)
Daytime Running Lamps (Don't believe I have this)
Transmission Control Switch (I understand this to be the overdrive switch)
I have done a lot of troubleshooting - starting with the most common...the wires in the steering column that control the overdrive. I checked those wires twice because I heard you have to check them very closely. So I even took the extra step of tracing them and disconnecting them at the plug near driver's feet. No joy.
I then disconnected the vacuum solenoid under the airbox in the engine compartment. No joy.
Next I went for the backup switch. I believe I located it on the driver side of the bell housing - it was a two-wire connector. Disconnected it. No joy. While I was in there, I disconnected the transmission range sensor too just to make sure the switch wasn't integrated into it. No joy.
I then removed both tail lights and disconnected the wiring harness that goes to the backup lights. No joy.
A trailer hitch was added before I owned the truck. The wiring looked suspect so I cut all of that out. no joy.
Every now and then, the fuse will hold for a few hours or longer - but it's totally random.
With the fuse blown, the 4x4 still works (high and low), the backup lights do not work and the Overdrive doesn't work.
All I have done recently is replaced the entire front end on both sides (upper control arm, lower control arm, sway bar end links, and outer tie rod ends). This had it's own set of challenges since I had never done it before, but the only thing that would have been any bit related to this fuse problem is that I was unable to get the c-clamp to release on the wheel axle so I had to do the job without removing the axle which turned out to be a lot easier. Why is this related you might ask? Well, it probably isn't, but the 4x4 vacuum relies on that hub and I tried in vain to get that axle off. I am 99% sure that there is nothing electrical in that axle and it's all vacuum-based, but I wanted to mention everything I had done.
Thanks for any help!