Since my 2007 silverado is going away soon, we've bee trying to update the 2000 blazer. just replaced the water pump and thermostat housing. While looking around i notice a bunch of vacuum line were dry rotted. replaced it all, even under the actuator. at first i had lights again at the switch in the dash, but putting it in neutral and trying to engage the 4wd was unsuccessful. Now no lights at the dash switch. all 4wd fuses are good ( I think). watched a bunch of videos from the forums here and youtube. I haven't actually checked the diaphram on the actuator yet ( will do this on monday) or the switch on the xfer casing.

Is that about it or is there something else to check? Thanks in advance.

 

Well duh, after researching a little more on this site, i find that i don't have the vacuum switch on the xfer case. i got the 4 button switch on the dash and i know where the switch is since i replaced the vacuum lines up to that switch last week. on to some testing later today.

 

That switch is just for the front axle 4WD engagement. If you have no lights in your controls you have different problems than vacuum lines and the front axle acutator. There is more than one fuse for the Automatic 4WD system, which is controlled by the TCCM module which is interfaced with the PCM. 4WD is also tied in indirectly to the ABS system. Amazing what they have done to accomplish the same thing as pushing a lever and turning the front hubs to lock them in.

You have a NV236 transfer case. Read and digest this - then ask any questions you have about diagnosing your vehicle. In your case you will want to start by checking all fuses, and then the connections on the TCCM for corrosion. There is an ATC fuse, a 4WD fuse, and a crank fuse feeding voltage into the 4WD system.

https://blazerforum.com/forum/tech-a...rmation-41198/

Ignore any "this fixed my 4WD" posts you may find on the Internet that you think sounds like your problem. Tons of misinformation out there.

Best wishes

 

Thank you lesmyer. I will 'read and digest' and report back. probably will be a few days, tho, since I live on the east coast (Charleston, sc area) and we're getting kind of inundated with some rain right now...

 

ok, all fuses are good. it's weird, sometimes the indicator light comes on and sometimes it doesn't. i've tried putting it in 4w hi, low and auto, but the indicator lights just seem to jump around and it does not go into 4wd at all. still have not had the time to test the actuator or examine the tccm.

Lesmyer, i'm no electrician when it comes to reading those scematics or using a multimeter. guess i'll try to get my brother in law down here with his meter and see whats going on. What should i be checking? the tccm? thanks for any advice.

 

ok, went out and cranked up the truck. none of the indicator lights were on. put her in neutral, and pressed the 4w hi button, the light blinked momentarily, then it sounded like it went from 2w hi to 4whi then back. then i just held the 4whi button in for a few seconds and i definitely heard it go, did the same for 4wlo, definitely heard it go. it didn't make the same sound then going back into 2whi tho, but it went. there's a big diff in 4wlo and 2whi of course. but after all that, still no indicator lights. now this morning, i went to the dentist about 8am and the 2whi indicator was lit. 30 minutes later going back home no indicator light.....

 

could be just dirty connections. The cluster of buttons the dash should pop right out. Good place to start

 

thanks newguy, i'll give that a try tomorrow. watching sec football this afternoon.

 

popped the dash switch out. looks all nice and clean still. jiggled the wires and the lights went on and off. unhooked the 2 connector and reseated them, but still the same thing. maybe a new switch?

 

Could be a bad switch. probably can test them with a meter but not sure how