I read a while back that the improved AC Delco part had a certain color paint mark on it, but heck if I can find it. Anyone know the p/n?

Rock Auto as well as other parts stores only carry Dorman.

 

Don't know the p/n however I know where it is located. It is the vacuum switch that sits on the top of the transfer case. It applies vacuum to the front axle actuator under the battery to lock in the front axle in 4WD.. It is not electrical, it is a vacuum switch with three hose connectors on the top of it. It takes a 7/8 wrench to loosen it, if you can get to it. If you have a lift kit, it is easier to access..


Hope this helps...


Bill

 

Found it: p/n 89059420

https://www.rockauto.com/en/parts/ge...t+switch,10775

 

What is your blazer model?



I have 4wd issues as well.. the actuator under the battery trey doesn't move at all when I press the button. The vacuum hose however is routed to this device that sits right above the distributor and not to the transfer case.