At the top of the engine bay of the drivers side there are three vac hoses all connected together at a T fitting. One hose (7/32) runs to the hvac system under the throttle body. Another hose(5/32) leads to somewhere into the fender. And then there is another hose(5/32) that is exposed and is about 5" long that leads to nowhere. I capped it with a screw which fixed my heater vent control but would like to know where it plugs into. Any help would be great! Thanks!!

 

I just replaced that hose and worked on the vac system on my 98 Blazer. Is yours a 4x4? I ask cause the way you are explaining it that hose you capped off is the one that should run down behind the motor to the transfer case to the vac switch and back up to the actuator under the battery to engage the front diff. Yes I had the same problem with my dash vents where it would only blow out the top no matter where the switch was set. The hose that runs to the fender is the vac storage container (I think that's what it is called) it is located in the fender you can't take it out but make sure the hose is connected what a pain to do. any way hope this helps

 

Yes it is a 4x4. So this hose I capped off leads down to that 3 way switch?? It must be corroded and ripped off because I just replaced that trans switch and on my old switch all three vac lines were still connected

 

It does definitely. So the hose I capped off just run to that vac switch on the trans case correct??

 

Do you know which of the three the hose connects to? I don't want to start pulling in hoses in hopes to find the right one

 

Once I was under the truck and unplugged the three way rubber boot connector which is on the drivers side of the transfer case the lines run over the top of the transmission to the passenger side I pulled it over there. Cut the plastic tie wrap (holding the lines to the transmission) off so I could get enough play in the lines to pull gently on to see which one is the one I wanted to replace. I was lucky enough that mine only had a hole in it and was able to use it to pull the new one through. Just remember to leave them connected to that boot and only remove the one you want to change. Once you pull on the one that is broke It will become clear quickly that you have the right one since it is broke all the way. You might want to take a few minutes to look at the top of the motor behind where the distributor is to see if you cant find the other end of the hose. Mine runs over the power booster for the brakes then down behind the engine to the passenger side. I went to autozone and got their standard size hose it is 5/16 the larger of the two sizes.

 

Right the hose runs to that switch on the transfer case. No once under the truck you can't tell which one is which you have to gently pull on it (just be gentle). Without this hose connected your 4x4 wont work.

 

my bad it is the 5/32 hose the larger of the two sizes that Autozone sells you will need about 6 feet to replace it all other wise you have to get some fittings to join pieces together

 

Perfect. Thanks everyone!! Huge help. Merry Christmas

 

The 3 lines that go to the transfer case vacuum switch are all 7/32". Only one of which comes from the vacuum source, (vacuum tee). The other two lines go up from the vacuum switch and over the transmission. One ends at a filter on the transmission dipstick tube. The other goes to the vacuum actuator under the battery.

The two 5/32" hoses: one goes to the vacuum reservoir in the driver fender and the other goes to the hard black plastic vacuum line for the HVAC.