Three port vacuum switch doesn't exist....
 

My 2001 S-10 Blazer LT with a 4 button 4WD switch will not engage the front axle. Like many, I have the dreaded no-vacuum problem with my (new) vacuum actuator. When I went to replace the 3-port vacuum switch on the transfer case, I realized that I did not have one. Mine has a single vacuum hosecoming out ofthe TC via a plastic elbow and ending up at the actuator (see picture). I have also replacedall damaged vacuum lines and the electronic TC switch on the front differential.

I have searched this site looking for something similiar, but have come up empty handed. My questions:

Why is mine different?
How do Ireplace it?

Thank's in advance for any help at all.

[IMG]local://upfiles/10559/F1800A81A01F4C69A97F16B39B877BFF.jpg[/IMG]

RE: Three port vacuum switch doesn't exist....
 

The Automatic Transfer Case doesn't have the 3-port switch, the manual does (IIRC).

Simple enough......
 

Hey, thanks for the info ZLover4Life. I guess that answers my first question. So that just leaves me wondering why I'm not getting vacuum to the actuator. Does this meanthat something inside my TC is messed up? Or can I pull that elbow piece off and check for vacuum, orreplace it?

I just don't want to mess things up worse than they already are. Not having 4WD is bad enough,replacing theTC is worse.

RE: Simple enough......
 

If you have the Auto T-case (4 button switch) your truck has a vacuum SOLENOID instead of the switch. The solenoid is mounted almost dead-center on the firewall, right above the engine distributor cap. you probably just have a rotted hose in that area...

RE: Simple enough......
 

Check my thread out https://blazerforum.com/m_185460/tm.htm I haven't found whats wrong with mine yet as I'm so busy studying for finals. But there is a pic, kind of small, and a lot of other info.

maybe Bill might want to take a stab at it if he gets a chance?

RE: Three port vacuum switch doesn't exist....
 

What you have circled there in the picture you posted is the vent for the transfer case. As already stated, you do not have a 3 port vacuum switch on the NV236 transfer case. The vacuum solenoid on the firewall is fed with manifold vacuum and the TCCM opens the solenoid to engage the front axle when necessary.

Right in front of my face.....
 

Yep, you all were right. Thank you.I checked the vacuum solenoid valve on the firewall for vacuum. I had strongvacuum to it coming from the manifold, but no vacuum to the actuator when a 4x4 button was pressed.I'm pretty sure this is my problem. Found a new one (GM Part# 15165891) at GM Parts Direct for $31.00. I'll reply back when it arrives.

I did a little more searching andit seems that a lot of 2001 LT's are affected with this same exact problem. Maybe just a flaw for that particular year.

Anyway, thanks again for all your help, I mean it.

RE: Right in front of my face.....
 

Fair warning, I have the exact same issue you're having (vacuum into the switch, none coming out), but replacing the switch did not resolve my problems. Please be sure to let us know how it works out for you.

RE: Right in front of my face.....
 

That's a VERY simple diagnosis to make, just unplug the two-pin connector from the solenoid, put a test light accross it's 2 terminals, key on push the 4hi button. If the test light lights, the solenoid is bad. If it doesn't the wiring between the TCCM and the solenoid has an open, or the TCCM is bad.

****ing ice!
 

Well, I didn't have a chance to receive my new vacuum solenoid valve before we got 2" of ice and 2" of snow dumped on us here in Missouri. So, I took the old valve off the firewall bracket it was in and smacked it against the top of the fan shroud about 3 times really hard, then plugged it back in and it finally locked the front axle into gear. I know for sure that it was working because I decided to play in the snow and ice, had no problem getting up an unpaved hill at all. I still haven'tinstalled the newvalve yet.

The only weird thingis my indicator light on the dash-mounted switch is still blinking in 4x4 mode continuously. It doesn't switch back to 2HI ever, just stays on 4HI (blinking, of course).
I pulled the switch out of the dash and was instantly furious as to what I saw, a very bad splice job on just about every wire going into the 8-pin connector, plus a wire (I can't find) completely missing from the bottom 2-pin connector. I'll try to post apicture of it.



I'mconvinced that this would be why thebutton keepsblinking.Anyone else agree?