Hello, newbie here.

Hoping someone could help.

I have a 1996 Blazer 4 wheel drive. In the dash is the 4 wheel drive switch - 3 switches total in one - one for 2wd - one for 4lo - one for 4hi.

The problem started recently where the switch was acting up - about 25% of the time it would allow 4 Lo and engage while 75% of the time it would indicate it was in 4 Lo but rather it was in 4 Hi making it difficult to climb our driveway. After playing around with it - it would eventually go into 4 Lo and all good.

The switch always would be illuminated when in use until the other day where it went dead - no lights whatsoever nor could I make any changes to the drive it was in - now stuck in 4wheel Lo. I checked the fuse, the lines, the line to the tranny all looks good.

I ordered an aftermarket switch brand new thinking that was the problem and when it arrived installed it today, still no lights or anything and the truck/blazer is still stuck in 4 wheel drive and we cannot go anywhere fearing we will fry the transfer and tranny.

Has anyone ran into this issue and can offer a suggestion on where to troubleshoot or what to do?
Thank you in advance!

DB

 

Check your vacuum actuator lines.

 

Take a look at this. It's just my own layman's version of how I troubeshoot 4x4 issues. Key thing to do is the TCCM dianostic test. Takes a little time to read the instructions and comprehend, but it beats throwing money at the problem.

 

 

Are any noises that sound like clicking coming from the passenger side kick panel? That is where the Transfer Case Control Module (TCCM) is located which has relays that control the electrical controls of the 4wd system. You should be able to hear them click once or twice when after pressing each of the 4wd control buttons. Sometimes they click a lot as if they cannot decided what to do and sometimes they are completely quiet. Either of the last two cases mean the TCCM is not working. Sometimes the fix can consists of unplugging the wire harness to it, cleaning the terminals and plugging it back in. Sometimes, like with me, I had to replace the TCCM.

Since the front axle engagement is by a vacuum controlled actuator (located beneath the battery on the 2nd generation ones) vacuum system problems can be a problem. Oftentimes the vacuum system issues for the 4wd system are also accompanied by issues with the HVAC system that is also partially controlled by engine vacuum. As these trucks get to or exceed the 20 y.o. mark, at least checking these vacuum lines or replacing them is probably a good idea no matter what.

Finally, I've read on this forum of the possibility of the cable that is controlled by the vacuum actuator getting stuck in one position or another.

Let us know what you find out as you try to diagnose the problem. Be sure to post what worked to get it fixed too.

 

 

I listed all of the ways these system fail that I know of. Regarding the vacuum, you are correct that I cannot see how a lack of vacuum could result in the front axle being engaged but I've learned to never leave out any possibility.

The thing about the vacuum system is that even if it is unrelated to your current issue, it is well worth the time to replace the vacuum lines because they eventually will start to leak.

Good luck with the repair.