why is the blazer not shifting into 4-wheel drive?

It could be any of these. I found a forum for you that walks somebody through diagnosing it. Hopefully this will help! http://www.carjunky.com/messageboard/data/1099.html

old body s-10 almost allwaya a bad switch or pluged vacc.line

It depends... are you letting off the gas when you shift into 4-wheel? Because thats the problem I've always had... I forget to let off the gas.

There is a vacuum line that runs from underneath the blazer that likes to come undone. It has happened to me, if that is the problem you just need to trace it back to under the hood and rehook the vacuum line

sounds like a bad acuwater,locaded under battery tray,is a round plunger like deal has a rubber diaphram.replace this your 4x4 should work 40 bucks at chevy dealer.

this propblem can be caused by 1 the encoder motor/transfercase motor 2 the transfercase switch 3 vaccum actuator under battery tray 4 broken cable from actuator to front diff. now we know the possible problems lets check them individualy fist the encoder motor when your in nutral and press the 4hi button does it flash and just never go in? can you hear an electric motor? after you press 4hi get undernieth the blazer and check if you can turn the front drive shaft by hand? in not this is a good thing and means your transfercase is locked in four wheel drive. if you can turn the drive shaft by hand i would replace the encodermotor (any where from 130$-150$ at a parts store and you do the work your self second is testing the vaccum lines after your transfer case is locked there is one line going from the back of the plenium to the switch on top of the transfercase when the engine is running it should have vaccum when you put it in 4hi it switches the switch and provides vaccum to the front actuator under the batery tray (this is the hose i think one of the privious posters talked about) make sure there is vaccum to the hose when in four wheel drive and if there is no vaccum i would replace the vaccum switch (10$-20$ at parts store and you do the work your self) if there is vaccum then you need to test the actuator it self you should be able to see it move when 4wheel drive is turnd on and off if it dont move the diphram could be tore and if it does move then very very very unliky your cable from the actuator to the front differntial is broken and i dont know what would be wrong hope this helps let us know when/if you fix it *the picture is of the actuator under the tray

rock it back and forth in drive and reverse and the light should go out.

under the baterry ( you also have to remove the battery box) there is a vaccum pod which shifts the transfer case from 2 wheel to 4 wheel check to see if its bad

I just fixed this problem on my 2000 blazer. It was the 4 wheel drive solinoid Napa part # 600-2296. I didn't buy it at Napa. I found one in the Salvage yard for $15.00. My was located in the middle of the firewall. It actuates the actuator under the battery. I found this problem by reading the posts on this site. Saved me a lot of money and I appreciate it. THANKS

In some cases UT would be the vacuum actuator located on top of the transfer case, it could be a 3 prong or a 2 prong that has vaccine lines going to it, it gets clogged and won't engage

i hve 2000 blazer it wont shift into 4wdrive when hit button it say awdrive i just dnt get it and light says serice 4 wheel

On my 96 blazer it was getting no vacuum to the actuator ( some but not enough to pull the cable) so I replaced the actuator and cable. Still nothing. I replaced all the vacuum lines and the vacuum switch. Still not enough. I knew it was had to be something in the transfer case vacuum switch because I hooked a vacuum line directly to my actuator and it worked. so it was getting vacuum to the switch just not exiting. I took the switch off leaving the lines on the switch pushed the ball in to activate the switch. I noticed that the actuator was still collapsing some but not enough. On top of the vacuum switch is a rubber adaptor that the lines connect to. I took that off and hook the lines direct. and it fixed the problem. obviously the adaptor was not getting a tight enough seal on the switch to contain the vacuum. hope this helps

do this remove the battery and tray. inspect the actuator under the battery. make sure the cable moves freely. hook the battery up start the blazer. unhook the battery, take it out. see if the actuator has collapsed and pulled the cable. the actuator should collapse all the way if proper vacuum

my 4 wheel drive will not do anything. it use to flash in hi but not go into 4 wheel drive. it would go into lo, but not high range. now when I push the buttons it will not even attempt to change. no flashing lights, no nothing. what could this be?

it sounds like your transfer case shift motor is seized I had the same problem and just replaced mine and now it goes in and out without any problem

My 2000 Blazer works in all drives as long as i have 15 amp fuse it the slot , it (calls for 10 amp .) been all over the truck looking for bear wires an shorts , can't find any , Any ideas?

It will go into 4w when u push the 4w low, but when u push the 4w high button it goes back to 2w

Thanks everyone I replaced the shift motor witch was seized I also replaced the accurater and the cable also the vacuum switch and everything works great.

On 1993-1994 s10 Blazers etc, the tccm (transfer case control module) looses ground. This causes it to work some of the time , or not at all. Ground black wires at tccm 10c, 12d,13d (the black wires) also you need a good neutral s/w , as it also completes the ground to engage Low range. tccm extreme R behind dash,

Looking for that box the front axles go in to ....what is that front box called

Need help.. 93 Sonoma s15 4.3v6. Transfer case switch is electric...mounted just above where the cable enters the tcase. Not the the 3 hose vacuum switch seen all over the inter web. The Vacuum hose that connects on the bottom of the actuator from the tcase...broke at the tcase end. Can't locate where we would re attach the new vacuum line to the tcase. Can't see anything in there can't feel anything . Does anybody have a picture or diagram of where this vacuum reconnects to???

If 97 to 05 blazer shifts into 4lo but not 4hi climb under with gunk carb cleaner, spray the shit out of it, scrub transfer case motor and linkage with tooth brush and spray it again. Works every time

The little round moter on my trasfrecas make the sound of it kicking in and out but the front ind is not gon in to make the wells spine

Try replacing the Transfer Case Control Module or unplug the wire harness from it and spray some electrical contact spray in to clean the wire harness and force some dielectric grease in the ends of the wire harness. I am about to do this my self. I have a 2004 S 10 Blazer and I am on my 6th transfer case Encoder Motor and now I push the buttons from 2 Hi to 4 Hi and apparently my push buttons are lighting up as both 4 Hi and 4Low at the same time. I went to disconnect my battery cable and left it go for a wile then reconnected the battery and pushed it into 4 Hi and it went right in immediately. So this tells me that if I went through this many Encoder Motors. I suspect its the TCCM Module. Right on the passenger side down below at the kick panel. I am about to try this myself after reading similar forums which led me to try out myself. Good luck everybody.

Hello, I have a 1997 blazer s10. It will go into 4w when u push the 4w low, but when u push the 4w high button it goes back to 2w. Any ideas? I replaced the dash push buttons when I bought it as they we're broke and also the fuse for the dash lights#3. I just bought it so I don't know to much of the history.

I have a different scenario to share that may help someone else who has this problem. Problem: clicking sound while in 2wd at low speed. The vacuum switch on the transfer case was stuck open so the front axle was always engaged but the transfer case actually shifted properly. I couldn't tell because the electronic axle switch was bad as well so the lights on the 3 button 4x4 control all looked perfect, e.g. I would select 4 hi and it would shift andI could confirm it was in 4x4. Same with 4lo. 2hi would look as if it worked properly and in fact was not in 4x4 but the front axle was engaged all the time.

I am lost... I have a 98 Blazer 4x4, bought it about 2 years ago. The 4wd didn't work so took it too a shop and had everything replaced, pertaining too the 4wd... No problem until a week or so ago. Now I keep blowing the #15 10 amp fuse and the push button (3) switch lights up when it wants on the dash. I think maybe I just need a new 4x4 switch?

Tybird01 it’s the 4x4 switch I had the same issue in 2wd on my 97 s10 blazer, clicking noises, this can cause serious damage if not fixed. The part is like $15-$20. Has a ball at the end that sticks and doesn’t disengage completely. Changed it and sound was gone and shifted even easier

2000 blazer push to go into 4 wheel drive lites lite up, it makes noise like its going into 4 wheel but stays in 2wheel any thoughts out there? Just bought it and did work!

Hello all of, you are very helpfull. I’m going to use all of yours suggestions in this matter. I wonder why it works when I turn off and on the engine and in same time press one of the buttons?

I found that when you have problems with the transfer case or you changed parts on it to pull the number 5 fuse and wait about 30 minutes place the fuse back in then turn the key forward so the lights come on, wait for the seatbelt chime to stop then turn the key off, do this 6 times, on the sixth time start the truck. This will reset the four wheel drive back to factory.

I want to turn off my 4x4 from engaging on till I fix my front right CV axle. I just want 2 wheel drive till I get the parts I need to fix it have to get the switch fixed too it doesn't work half the time the lite keeps going out.

I know this is an old thread, but I had the issue with the NP8 transfer case where it wouldn't go into 4WD or Auto mode. The LEDs on the switches would just blink. Turns out it was a failed vacuum hose that goes from the vacuum tee (that's mounted to the engine) to the check valve that's near the power brake booster. I was getting no vacuum to the actuator under the battery tray, and this prevented 4WD operation. A new piece of hose and all is well! The 20 year old hose appeared to have deteriorated and fallen apart due to heat and fuel vapors.