98 Blazer 4WD issue


whoareyou4
06-04-2010, 02:26 PM
When I select 4WD (I have the 3 button switch), I get a few clicks from the TCCM and then nothing, the 20 amp ATC fuse blows. The other day I removed the Transfer Case Vacuum switch, the ball was difficult to move in and out but I worked with it for a while and it seem to move easier so I reinstalled the switch.
I then tried to engage 4WD and it worked, the actuator appeared to go in and out solidly. When I drove the vehicle and pushed the 4WD button I got a loud whir like it was not fully engaging the front wheels.
The next day I replaced the vacuum switch with a brand new one because when I removed it again the ball was real difficult to move. Now I am still blowing the ATC fuse. The connections to the shift motor are good and clean, as well as the connection to the switch near where the actuator cable enters the front diff.
It looks like a mouse may have eaten through part of the casing on the actuator cable so I am replacing the cable this afternoon. If this does not work than I don't know what else to check. The way the front end was engaging the other day I feel confident I have vacuum at the actuator, I can't check now for sure because the fuse blows so quickly. of course there could be a bad ground somewhere but I don't know where to check.
Any ideas? Am I missing something?

MT-2500
06-04-2010, 03:26 PM
When I select 4WD (I have the 3 button switch), I get a few clicks from the TCCM and then nothing, the 20 amp ATC fuse blows. The other day I removed the Transfer Case Vacuum switch, the ball was difficult to move in and out but I worked with it for a while and it seem to move easier so I reinstalled the switch.
I then tried to engage 4WD and it worked, the actuator appeared to go in and out solidly. When I drove the vehicle and pushed the 4WD button I got a loud whir like it was not fully engaging the front wheels.
The next day I replaced the vacuum switch with a brand new one because when I removed it again the ball was real difficult to move. Now I am still blowing the ATC fuse. The connections to the shift motor are good and clean, as well as the connection to the switch near where the actuator cable enters the front diff.
It looks like a mouse may have eaten through part of the casing on the actuator cable so I am replacing the cable this afternoon. If this does not work than I don't know what else to check. The way the front end was engaging the other day I feel confident I have vacuum at the actuator, I can't check now for sure because the fuse blows so quickly. of course there could be a bad ground somewhere but I don't know where to check.
Any ideas? Am I missing something?

If it is blowing fuse you have a short some place.
I would start unplugging until you find short.
Check a wiring diagram to be sure but I think the fuse is tied into some other stuff besides 4W shifting stuff.
Also grounding pin 13 on diagnostic connector should read out codes if you have any.

MT-2500
06-04-2010, 03:42 PM
The ACT fuse only powers the transfer case control moduel on yours.
But then the module powers the transfer case motor from ACT fuse power.
Check for shorted or overloaded motor and wiring.

Check amp draw on motor if 15 or more amps you have a motor problem.

whoareyou4
06-04-2010, 04:11 PM
The connections on the TCCM are good and clean as well as the connections to the encoder motor. I believe the encoder motor is good. Connections are good at the 3 button switch

MT-2500
06-04-2010, 05:02 PM
The connections on the TCCM are good and clean as well as the connections to the encoder motor. I believe the encoder motor is good. Connections are good at the 3 button switch

If blowing fuse you have short or motor pulling to many amps.
Check motor amp draw.

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