I have a '98 blazer that has had some issues with the 4wd shifting that have seem to have gotten worse today. The problem started with the lights on the buttons just turning off (all of them) after driving for awhile,l but if you pushed them a few times, the 4wd would engage and disengage, although it seemed to be struggling, and sometimes you would have to shift it in and out before it would go.

This morning, after using the 4wd yesterday, I drove into the driveway, and when I made the turn, I realized that the front axle was engaged, even though I thought it was no longer in 4wd. i pushed the buttons, and heard the clicking from the dash as usual, but nothing was happening underneath the vehicle like it should.

I checked the fuse in the engine compartment (ACT #15 I believe), and it was blown. I did not have a spare 20A, so I put in a 15, and tried to shift it out, and same thing, blown fuse. So, figuring if it was going to be broken, I would go for broke, and try to at least get it stuck in 2wd, and get the axle to unlock, I jumpered the fuse with a wire. This got the axle unlocked, but the transfer case motor still didn't make any noise, BUT, the dash light now reads 2wd like it should, and has stayed on since then.(I removed the wire from the fuse socket, and just left it open).

Am I correct in assuming that the shift motor has gone bad? Is that what the ACT (active transfer case according to the manual) protects, and if I replace the shift motor, everything should work again? Is there a way to test the shift motor?

Any help would be greatly apreciated.

Thanks, Jeff

 

GO to one of the help links in my signature and you should find a thread called 4x4 no worky . see if that helps you. GL

 

This didn't really address my question about why the ACT fuse is blowing, and what it is actually connected to.

 

I think you mean ATC. Check out the NV236 Wiring & Diagnostic Information thread in the Tech Article section. It has the wiring information for the NV236 transfer case. The ATC fuse is used exclusively by the shift motor, specifically to lock/unlock the motor as well as power it to shift the transfer case. It does go through the TCCM. I would inspect all of the wiring connections for corrosion and while you have the wiring disconnected, test for continuity to ground, especially on the lead from the TCCM to the encoder motor for the motor control (large black & red wires at the TCCM & encoder).

You can also test the motor resistance while it is disconnected. It should read relatively low. If it reads off the scale, especially right after you have tried to shift the transfer case & blown the fuse, then the encoder motor is bad.

 

Just wonderein if you ever got the blown fuse problem, mine is doin the same thing.