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  #1  
Old 12-05-2011, 09:40 PM
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Default 1998 Blazer 4wd Wiring Diagrams Please!

HI, does anybody have wiring diagrams that show all or some of the 4wd circuit, which is Fuse 15 in the I/P fuse box?

I'm trying to track down a short in the 4wd circuit and cannot find the diagrams anywhere.

Oh, and the 4wd is the 3-button (2-hi, 4-hi, 4-lo). NP233 I think?

Thanks in advance!
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Last edited by Mark_D; 12-06-2011 at 11:50 AM. Reason: Adding technical info
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Old 12-06-2011, 11:48 AM
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Ok, well as a start, does anyone know the exact location of the grounds for the dashboard electronics? I was told there should be one right by the driver's left knee. I've seen that screw but aside from the aftermarket security alarm (which I removed) nothing else was attached to it. I am looking because I'd like to double check all of the grounds.

Thank you!
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Old 12-06-2011, 12:01 PM
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Can't view my own photobucket images from work, but this tech article should have the wiring diagrams.
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Old 12-07-2011, 12:14 PM
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Thanks! The image with the grounds will definitely help, as I plan to go find them after work today.

I managed to remove most of the 4wd components from the list of suspects since I can shift between 2hi and 4hi no problem when the engine is off (4lo needs to have the engine on, and it should work too).

I suspect either a faulty ground with a circuit that is hot only when running, or wires from a similar circuit crossing into the 4wd.

Thanks Swrtlkk! I'll post the outcome tonight...
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Old 12-07-2011, 01:09 PM
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For a 2000
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Old 12-08-2011, 06:58 AM
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Thanks for the schematics guys! I got under there last night and found the ground wires and they appear to be tightly connected. They were behind a rubber sheet and foam padding and were a real pain in the A to get to though.

I'm going to test those 2 grounds (3 wires, 2 studs) though. I had to stop because it was nighttime next to a quickly rising creek with a flood warning in effect This evening...
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Old 12-11-2011, 03:34 PM
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So I checked those grounds on the firewall and with a multimeter, the grounding studs to the negative terminal on the battery read ~40 Ohms resistance. That seemed high, so I ran a new, temporary ground wire connecting those studs to the battery and the problem remains.

In fact, it seems like doing that might have burned up the 4wd selector switch because now no lights come on on the 3-light indicator, where they used to work and shift properly (before the fuse would blow, of course).

Does 40 Ohms resistance between a ground stud and the battery sound high to anyone?

I am thinking the time may soon be coming to pull the dash and inspect all the wires. Man, I don't want to do that...
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Old 12-11-2011, 07:37 PM
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40 ohms is too high, should be less than 5 ohms.
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Old 12-12-2011, 06:37 PM
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Thanks for the reply...I knew that resistance seemed high! I'll aim to check and fix the grounds one day soon.

Today I checked out whatever connector it is that is on the front axle on the passenger side near the spring engagement thingamabob. With this connector unplugged everything seems to work fine (no fuses blow, appear to be able to switch into 4wd, etc.). Also, that connector looks okay and is receiving power.

My question is what is that unit that this connector goes into called? It is held onto the front differential [?] by 3 bolts. I've seen it on a diagram somewhere in my travels but cannot find it again I'd like to change that part out and see what happens.
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Old 12-12-2011, 07:16 PM
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That is the front axle engagement switch. Fuse #15 sends battery voltage to it when the ignition is in the RUN position. When 4WD is selected, the actuator under the battery engages the right front axle clutch and the switch sends the voltage to the VCM confirming axle engagement. If the switch does not return battery voltage back to the VCM, (indicating that the axle is not engaged) the VCM "tells" the TCCM and the TCCM will set a code in its memory and the switch lights will blink telling you there's a problem.

This applies to the NV233 2 speed selectable transfer case only.
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Last edited by Captain Hook; 12-12-2011 at 07:19 PM.
Old 12-12-2011, 07:16 PM
 
 
 
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