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#15 4x4 fuse keeps blowing 98 blazer

Old Jan 9, 2020 | 12:45 PM
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Default #15 4x4 fuse keeps blowing 98 blazer

I am having this problem with one of my 2 98 Blazers.
221000 miles. Bravada axle swap. New Transfer Case Shift Motor (Confirmed working.)

I unplug 4x4 switch, unplug TCCM, Still blows fuse but only after shifting into gear and waiting several seconds with the engine running. When the fuse blows it takes out the 4x4 switch immediately but later the gear selector back light fails. When I turn off the ignition and then restart the engine the Temp gauge goes to 0 and fuel gauge goes to full empty. Low Fuel warning light comes on and battery light comes on constant but volt meter and oil pressure gauge are normal.

Fuse does not blow with key in run position but motor not running.

Anyone had further issues or solutions?
 
Old Jan 9, 2020 | 04:42 PM
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Originally Posted by Captpittman
I am having this problem with one of my 2 98 Blazers.
221000 miles. Bravada axle swap. New Transfer Case Shift Motor (Confirmed working.)

I unplug 4x4 switch, unplug TCCM, Still blows fuse but only after shifting into gear and waiting several seconds with the engine running. When the fuse blows it takes out the 4x4 switch immediately but later the gear selector back light fails. When I turn off the ignition and then restart the engine the Temp gauge goes to 0 and fuel gauge goes to full empty. Low Fuel warning light comes on and battery light comes on constant but volt meter and oil pressure gauge are normal.

Fuse does not blow with key in run position but motor not running.

Anyone had further issues or solutions?
Not sure how any of this relates to gauges or gear selector light, but this 4x4 fuse that is blowing has feeds to 4x4 selector switch, front axle switch, EBCM, and 2 points at the VCM via SP200. Maybe the attachments will help you diagnose where the short actually is. Let me know.
 
Attached Files
File Type: pdf
98 4WD Schematic.pdf (126.9 KB, 109 views)
File Type: pdf
98 4WD Schematic2.pdf (131.0 KB, 104 views)

Last edited by LesMyer; Jan 9, 2020 at 04:45 PM.
Old Jan 10, 2020 | 02:32 PM
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Les, do you happen to have a diagram of the entire 4x4 circuit? I think since the fuse still blows with the switch disconnected that should eliminate that as a cause shouldn't it? Same with the TCCM? The front axle switch is constantly "closed" as it is wired together after the Bravada Axle Swap. The only thing I have left to try is the see if it blows with the Transfer Case Shift Motor disconnected.
 
Old Jan 10, 2020 | 03:02 PM
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Originally Posted by Captpittman
Les, do you happen to have a diagram of the entire 4x4 circuit? I think since the fuse still blows with the switch disconnected that should eliminate that as a cause shouldn't it? Same with the TCCM? The front axle switch is constantly "closed" as it is wired together after the Bravada Axle Swap. The only thing I have left to try is the see if it blows with the Transfer Case Shift Motor disconnected.
Yes, if it's not hooked up it can't be the cause of the short. Maybe something down the line in the ABS system after the front axle switch (EBCM), or in the wiring? I don't think the encoder motor has a direct feed from the 4WD fuse but need to check.

The 4 schematics for the entire 4x4 circuit for 2001 NP1 is here https://blazerforum.com/forum/2nd-ge...-blazer-89670/

I'll try to post specific ones for the 1998 tonight as there might be some very minor differences.

Please confirm you have the 3-button NP1 transfer case, not the 4 button Auto NP8 transfer case. My service info for 1998 did not show any NP8 wiring, so I previously gave you the three button 1998 NP1 diagrams.
 

Last edited by LesMyer; Jan 10, 2020 at 03:12 PM.
Old Jan 10, 2020 | 06:31 PM
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Here's the other two schematics for the 1998 NP1
 
Attached Files
File Type: pdf
98 4WD Schematic4.pdf (83.1 KB, 115 views)
File Type: pdf
98 4WD Schematic3.pdf (92.4 KB, 120 views)
Old Jan 10, 2020 | 10:49 PM
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Yes. 3 button.
 
Old Jan 11, 2020 | 03:15 AM
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I would also suggest to have a look at all wiring concerned and look out for repair or splices.
We had so many problems with incorrect repairs here in the forum as well as at the place where I fix cars. Incredible repairs done by shops and garages which I would at best consider an emergency repair when stuck in the desert.
 
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