1995 S-10 Blazer 4X4 Problem

Our '95 Blazer has some 4 wheel drive issues. It is currently in 2 Hi. When I push the 4 Hi button, nothing happens. When I push the 4 Lo button the lights (4 Hi & 4 Lo) blink while it is in transition and it goes into 4 Lo. Sometimes with a 4 Lo light and sometimes without the light. Pushing the 4 Hi button sends it back to 2 Hi, sometimes with a light and sometimes without. I have checked to make sure that it is truly in 4 Lo and it is. The drive motor in the transfer case can be heard shifting and the controller behind the dash can be heard cycling but it wont go to 4 HI.

A couple weeks ago, it did the same thing. After screwing with it for a while, I got it into 4 Lo with the light on and shut it off. I then pulled the battery cable for about an hour. When I reconnected it, the stupid thing worked. It has worked for the last 2 weeks until today.

Does anyone have shop manuals with the schematics for this? Anyone have any suggestions?

Snowed in in Central New York!

My 94 is sort of doing to the same thing, I couldn't get anything to work, no 4hi or 4 low, no lights on the switch. Unhooked the battery for 1 minute, connected and then it started working again. I spoke to our local Transmission shop and its probably my transfer case computer/replay under the dash. Apparently its alot more than an relay like everyone thinks, considering they want $500 for a new one. Planning on digging one out of a wreck at some point.

Anyway let me know if you figure it out.

I did the battery disconnect thing today and it started working again. It seems to get confused if you change settings just before shutting the vehicle off. It has happened twice now. Both times I pulled it into the garage while going to 2 wheel drive. I didn't notice it at first because 2 wheel worked fine. It wasn't until I went to 4 that I found it inop. At $500 I'll keep nursing this along until it hard fails. I'll just be more carefull about going between 2 & 4. Thanks for your input. Let me know if you learn anything else.

Funny that you should mention the unit gets confused if you change setting just before shutting the engine off. The last time mine worked before it acted up I had just switched back to 2 hi then shut the truck off and walked away. I was thinking the same thing about a replacement, for that kind of money wait until it flat out quits. I should mention thats $500 canadian, so like after exchange its probably $2.50US or something. My problem with this truck is that Used parts from auto wreckers are hard to come by, the only blazer in there are like 86,88's. I guess that should stand for something if theres not too many in the yard yet.

Later,

it looks like it has been a long time sence you had this problem i was hoping that you could help me with a simular problem

3 Things that you should check for. 1st check the vac diaphram for tears under the battery tray. Second, check the vac switch at the vacum case. Third, and as a last resort, check your encoder motor. It will be one of these 3 things

thanks for the advice it looks like ive got a few things to check. by-the-way did your 3 lights(2H, 4H, 4Lo) flash 5 times then go out if so what did you find went wrong that led to you resolving the problem.

"3 Things that you should check for. 1st check the vac diaphram for tears under the battery tray. Second, check the vac switch at the vacum case. Third, and as a last resort, check your encoder motor. It will be one of these 3 things"

iv had the same prob...but with my 93 cpi/w.
iv had all these things checked...and were fine.
got a 4x4 comp from a yard..$75..and has been working for almost 3 weeks..i check it everyday since i replaced it. :/
the dealer told me..in most cases of...wierd shifting/no shifting are usually the comp..and he was right in my case.
btw....the 4x4 comp is the smaller box that piggybacks on the main comp(under pass-side of dash)
the 4x4 comp is more than just a relay...its a circuit board with chips...one being a rom that goes bad..just like computer memory etc do.

thanks for your help it looks like ive got some work to do.