1999 Chevy Blazer 4WD. The 4WD 10A fuse keeps blowing. I looked at the TCCM and to my "untrained" eye, it looks alright. The plug that goes into the TCCM also shows no real signs of corrosion. Those little pins are so small I really don't know how you see it. There are two other bits of info that may or may not be related to help you, help me troubleshoot. First, for the couple minutes I have before the fuse blows, I push the transfer case control switch and when I'm in N and push 4LO, it just keeps flashing and won't shift into 4LO. The only way to get it into 4LO is by taking the trucks gear shifter and moving it towards the P position. It shifts to 4LO right away then. Secondly, once in a while I keep hearing a sound that's like a grinding or sound like a card in the spokes of a bike tire. It gets pretty loud at times. I can only get it to stop by stopping the car and shifting from P to 3 and back. It seems like a short somewhere but I have no idea how to trace it. Please help?

 

The grinding you describe sounds like it could be the front axle partially engaging, which there is a lot of information about on this forum. Usually it is a problem with the vacuum [solenoid?] located under the battery or with the actuator cable that comes out of it.

The stuff you mention about having to switch gears to engage the 4hi, 4lo, etc. is normal. It is in the user manual for your truck also. You don't need to actually shift through all the gears to get it to shift, but I think you have to be in PARK for the 4lo to actuate. I think this is probably so that it is impossible to engage 4lo while moving and tearing your drivetrain apart.

Otherwise, i have the same problem with the 4wd fuse blowing, so I'm not of much help beyond what I've said above. Good luck.