First I want to thank this forum for giving me some ideas where to dig to fix my problem. I have an '04 Blazer with the auto 4WD set up. Well, as the first snows start to fall, my 4WD decides to quit. I would press the selector switch and all I got was blinking indicator lights in
Auto 4WD, 4Hi or4Lo. I had no clue if this was electrical, mechanical or what. Turns out a vacuum line came off of its nipple, disabling the entire 4WD system. Thisnipple is located on a plastic panel directly under the rear mounting bracket boltfor the ABS unit. It'sabove the drivers sidewheel wellback near the firewall. The line was kind of ratty so I replaced it with a 6" piece of5/32 rubber tubing and it did the trick. Hope this gets someone out of a jam.

 

I had the same problem, except mine was the nipple on the firewall, directly above the distributor. Another place to check!

 

same prob replaced that whole vacuum line.

 

My light blinks too. I will check for loose connections. I do not want to replace the vac actuator. But winter is near and i want the 4WD to work.

Thanks for the tips.

 

Sometimes mine tries to engage but it just grinds. Sometimes the light just comes on and thats it. Then every once in a while it will engage then stay on. It seems to me when it grinds then it is trying to engage but the actuator is getting stuck. I'm trying to figure out if it would be the actuator under the battery tray or if the mechanical actuator bolted to the front axle isn't working right. any ideas on how to check this out? I don't think it's vacume bacause it will actually engage now and again. I dont remember the temps outside when it did engage. Any help would be appriciated.

 

Ok, I took out the battery and the tray I checked the actuator thats there. The thin rubber cover is in perfect condition and everything else looks new. It looks like it was recently replaced. (we just bought the blazer a year ago). I also traced the vacume lines and the lines look fine they will have to be replaced soon but They are just starting to get a little dry rotted. I crawled under the front and I tapped/pounded on the actuator bolted to the front axle/pumpkin and I had 4wd. I believe I will have to replace that part. I have been searching thru the hanes manual and cannot find anything about this part. 1 little picture with the part in it and thats it. Can anyone tell me the proper name for this part so I can look into buy it or finding one used.

 

Can anyone tell me where to find the part #'s for # 10 thru 14 on this diagram. Somewhere in this rang of parts is causing me to not have 4wd because of the post I typed above.

What is # 11, is that a switch or something to do with vacume?

 

How free does the cable move? A lot of the time, the cable itself gets sticky to the point where the vacuum actuator cannot pull hard enough to engage it.

As far as part numbers, nothing that I have (which is a lot) has these part numbers. These would be straight from GM or a local junkyard. Other than it being winter now, the junkyard is your best bet if you really think that it is the components in the front axle. The best part about pulling items like this at a yard is that you get to see how everything comes apart on something other than your truck. If you make a mistake and break something, move on to the next 4wd s-series in the yard (they are plentiful in the yards near me).

I still would check the cable before going that far.

Greed, Please, if you have anything to add to your post and someone has not responded, use the edit function to do so. Posting consecutively in short order is frowned upon. Also, you may want to create your own post on your problem so that people can respond directly to your question instead of only to the original poster of this thread. Posting a question in someone elses thread is a good way to get your question overlooked. It also can divert attention away from the original question, but not in this case.

 

I will try to figure out how to do that. sorry, I just figure this would be better than starting several 4x4 threads.

How would I go about checking the cable? Do you recomend I remove it then check it that way.