trying to fix my 4x4 with minimal cost before snow it worked last season this season i tried it and it seems my fronts are not engaging. i replaced the t case switch the old one was bad still no 4x4. i changed the actuator which had a big hole in it still no 4x4. today i relocated the actuator from under the battery tray so i can see it when the truck is on hit the 4x4 button and it did nothing. pull the vacuum line off no vacuum but i manually closed the actuator with zip tie and i got in the truck punched it in the gravel and the backs spun so it seems i still have the same problem any ideas or am i screwed?

 

What year and model? 3 or 4 buttons on the dash switch? What switch did you replace: vacuum switch on transfer case, axle engage switch on front axle, or dash switch? Do you have vacuum at the actuator under the battery when the engine is running and in 4WD?

 

its a 2001 blazer it has 3 buttons 2wd 4hi and 4lo i never have vacuum at all at the actuator and the switch i did was the one with the 3 line on it on the t case

the dash switch when i hit 4wd it will blink a couple times then illuminate solid in 4wd and same with lo and in low i can hear the rear "klunk" engaging the rear end but the fronts never lock

 

The switch you replaced on the transfer case.... One line should have manifold vacuum whenever the engine is running. It comes from the vacuum reservoir in the driver side fender, near the hood hinge, you need a mirror and a flashlight or eyes in your fingers to spot it The line eventually ends up at the intake manifold. Another line on the switch goes to the actuator under the battery, (it might take a detour and go through an electric vacuum switch on the firewall). The third line tees into the transfer case vent and then runs up the transmission dipstick tube with a small filter in the end. Let me know what you find.

 

i know the one going up by the trans stick it sits between the heater hoses should that be capped or open? the filter is gone

 

Gotta be open, with a filter! When in 4WD the actuator has manifold vacuum to it. When you go back to 2WD the vacuum vents to atmosphere through that hose and filter. If it's plugged, 4WD will not disengage. If it doesn't have a filter, it will suck dirt into the system when the actuator vents to atmosphere.

 

ok so i gotta rig up a filter on that tomorrow but that wouldnt stop me from getting into 4wd so not my real problem i know a line is running into the fender i will see if i can get eyes on it tomorrow to make sure its connected is there a line behind the dash??? cuz my heater core was done and i am wondering if it got f'ed up then some how

 

Vacuum operates the HVAC and the 4WD. Without vacuum the HVAC defaults to defrost and 4WD defaults to 2WD. From the reservoir in the fender the line tees to one going into the dash for the HVAC. Probably one common problem for both of your issues.... loss of vacuum

 

oh my heats works properly so my issue is not in my dash i guess then

 

Check for vacuum at the reservoir and trace the lines, should be a small black & white, (or all black) vacuum check valve dangling close to the power brake booster, that all that stuff connects to. It looks similar to this: