93 blazer; no more 4hi and no sound while trying to engage

[Pristine1]

Just registered tonight so I apologize if I am posting in wrong place. I have a 93 blazer w/ rocker switch engagement (solid green in 4hi, amber in 4lo, blinking while engaging). If I push rocker switch to engage 4hi when I'm in gear and moving it doesn't do anything, no flash, no sound, squat. If in neutral and I try to engage 4hi both lights will blink and then shut off, so I know it's not the light that's bad. In neutral, it will shift into 4lo but is then a pain to get back out. 4hi did work when I first bought it a couple weeks ago. I even used it twice the day it stopped working and then that evening it just wouldn't do anything in 4hi. The owner's manual suggests to put in neutral, hit 4hi, and then put into park while blinking. It says that should get it in 4hi but recommends service to adjust something. Tried and failed several times. I don't understand why it goes into 4lo but won't even make a peep for 4hi. Any ideas, had 4 inches of snow today. Not fun driving rear 2wd with a light backend. Please advise. I did try to search other threads for these symptoms but everyone else's seemed to hear it trying to engage 4hi, mine doesn't make a sound. Thanks for any help.

[MT-2500]

Muddog has a how to that may help.
http://www.automotiveforums.com/vbul...d.php?t=572914

It might pay to check the switch for switching good.

[Pristine1]

I read muddogs post earlier. Does it matter that the post was regarding a newer generation blazer, with I believe a 3 button? If it's going into 4lo, could it still be the dash switch that may be bad? Let me ask it this way, if the vehicle will go into 4lo which requires vacuum, is it safe to assume it is not a vacuum problem? Or does lo and hi run off two different vacuum lines? I actually just got the hvac system working again the morning that the 4wd went out!?!?! This thing will be the death of me.

[MT-2500]

Originally Posted by Pristine1

I read muddogs post earlier. Does it matter that the post was regarding a newer generation blazer, with I believe a 3 button? If it's going into 4lo, could it still be the dash switch that may be bad? Let me ask it this way, if the vehicle will go into 4lo which requires vacuum, is it safe to assume it is not a vacuum problem? Or does lo and hi run off two different vacuum lines? I actually just got the hvac system working again the morning that the 4wd went out!?!?! This thing will be the death of me.

The vacuum parts is for front axel lock in and out.

On the older ones with the rocker switch the switch switches 12 volt power to the transfer case control module for transfer case shifting.

First test is for good 12 volts in to and out of rocker switch to the shift module.
Ans check all wiring and plug in and power feeds and grounds

I would suggest a good factory repair manual or a all data sub
For the wiring and shifting testing and repair flow charts.
Lot of good repair info and information in there.
MT

http://www.alldata.com/products/diy/index.html

[MT-2500]

Originally Posted by Pristine1

I read muddogs post earlier. Does it matter that the post was regarding a newer generation blazer, with I believe a 3 button? If it's going into 4lo, could it still be the dash switch that may be bad? Let me ask it this way, if the vehicle will go into 4lo which requires vacuum, is it safe to assume it is not a vacuum problem? Or does lo and hi run off two different vacuum lines? I actually just got the hvac system working again the morning that the 4wd went out!?!?! This thing will be the death of me.

The vacuum parts is for front axel lock in and out.

On the older ones with the rocker switch the switch switches 12 volt power to the transfer case control module for transfer case shifting.

First test is for good 12 volts in to and out of rocker switch to the shift module.

Also the park and neutral switch and/or clutch switch will shut off power to shift module also if backup light switch is pluged on backwards it will affect shifting.
And check all wiring and plug in and power feeds and grounds

I would suggest a good factory repair manual or a all data sub
For the wiring and shifting testing and repair flow charts.
Lot of good repair info and information in there.
MT

http://www.alldata.com/products/diy/index.html