Hi
My blazer 4wd not engaging, when I put it on 4th and 4 low lights keeps flashing. 4wd service lights not on. Please help

Ok guys juSt tried putting it in 4lo and 4hi I hear a noise like clonk, maybe it's the 4wd engaging but the push button light is still blinking. Any idea why it's doing it

 

please help

 

How many buttons are on the 4wd switch in the dash?

 

Found The pproblem. Vacuum hose was split. 4wd now working

 

What vacuum hose, where? I COULD GUESS somewhere near the actuaotr under tha battery, am I right?

Dang, you're a lot of help to anyone else with the same problem.

 

My question relates to a highly intermittent Service 4WD light, but I'll add to this thread since that's how it started almost 6 months ago..
2001 4WD with with the push button control and auto 4WD option. Went to put it in 4WD HI last fall. It engaged, but then shortly after started flashing. Service light NOT on. Would not go out of 4WD-tried other buttons, light flashed for a while, then went back to 4WD. Raised the front end; differential was NOT locked, so I knew it really wasn't in 4WD.
Started checking; vacuum line from bellows under battery was cracked/split. Replaced hose from bellows to firewall solenoid and from solenoid to manifold vacuum port. Still would not work. Turns out the solenoid was bad/leaking also. Once I replaced that, it let me get back to 2WD mode.

Things I learned for 4WD problems; check/replace vacuum hoses. The one from the solenoid to the bellows is about 5 feet long and snakes around the engine. It is important which hose goes to which port on the solenoid (top to bellows, bottom to vacuum T over by ABS control). You can check the solenoid by blowing/sucking on a short piece of hose connected to each port with the engine off. The top one will allow air through. The bottom one should NOT. If it does, buy a new solenoid. If you disconnect the electrical plug to the solenoid or it breaks, all the 4WD lights will flash and you can't do anything.

Now my question. After replacing hoses and solenoid last fall, all has seemed well. Except I will get a Service 4WD light come on after 30-45 mins of highway driving (in 2WD mode). If I stop, turn off the engine, then restart it, the light goes out. Shorter, around town, stop & go driving does not turn it on. The electrical connections look good/tight. Any ideas?
Also, when checking it today, I noticed the driveshaft from the transfer case to the front differential was engaged, ie I couldn't turn it. I would think it would be 'free' to cut down on drag/wear.