Transfer case vacuum switch

2003 s-10 ZR-2 4.3 4WD front wheels will not engage, light on dash 4Hi and 4 Lo light up and say they are locked but they are not. Heater is stuck on Vent. From all I've read the Transfer Case Vacuum Switch is pooched and it has allowed oil to be sucked into the Vacuum Activator under the battery which explains why it won't pull the cabel and engage the front wheels. Also fluid has been sucked into the Heater control and I've read 3 other things that all need replacing for the defrost/heater/vent to work correctly. What exactly do I need to purchase for parts and is there somewhere that explains the easiest method to access and replace them. I found a great write up on the TC Switch and 4WD activator, but nothing on the heater proceedure.

2003 s-10 ZR-2 4.3 4WD front wheels will not engage, light on dash 4Hi and 4 Lo light up and say they are locked but they are not. Heater is stuck on Vent. From all I've read the Transfer Case Vacuum Switch is pooched and it has allowed oil to be sucked into the Vacuum Activator under the battery which explains why it won't pull the cabel and engage the front wheels. Also fluid has been sucked into the Heater control and I've read 3 other things that all need replacing for the defrost/heater/vent to work correctly. What exactly do I need to purchase for parts and is there somewhere that explains the easiest method to access and replace them. I found a great write up on the TC Switch and 4WD activator, but nothing on the heater proceedure.

First thing is to check for good engine vacuum to heater and 4W.
Look for any bad vacuum hoses rubber /plastic and fittings.
Does heater control have good full engine vacuum to it.

Is this a 3 or 4 button switch system? I am assuming is a 3 button one. If its a 4 button one, the actuator for the cable is engaged by an electronic solonoid under the hood on the firewall, on top of the distributor, with two vaccuum lines coming out of it. If its this type, then you do not have a transfer case switch, and your explanation with fluid in the vaccuum lines does not apply.

Now if you have a 3 button switch, then your explanation applies. The vacuum switch seal breaks and allows fluid to be sucked into the vaccuum system causing all sorts of issues. If you have oil in the vaccuum lines, you need to get that cleaned out, the 4wd vaccuum switch needs to be replaced, which is located on the top of the transfer case. it is accessable by getting under there and reaching over the top of the case to find it. For the heater controls, you need to unplug it from the inside and clear out the fluid in the lines.

BUT, before changing things, like MT mentioned, first test for vaccuum and make sure that is yourproblem before throwing parts at it.



Hope this gives you some idea.