4wd problems

jmelrntz · December 12, 2005

i have a 92 k2500 with the 8600# gvw. was out plowing the other day and all of a sudden, no more 4wd. don't have it in hi or lo. light doesn't come on. i'm guessing its either the actuator or the transfer case switch. the actuator i have, which i believe is supposed to be the thermal actuator, has a brown wire on the actuator side of the plug. there is no brown wire on the truck side which i know there shouldn't be on that side. should there be on the actuator side tho or did someone replace with the wrong actuator? the 4wd worked fine until yesterday. i did check the fuse when it went out and it was blown, i replaced but this didn't help anything. it did not blow the new fuse. the front driveshaft will engage so i'm assuming it has to be either the actuator or the switch. any help/suggestions? also do you have to take out the t-case to replace the switch? and is it just a contact switch?

GM-Tech · December 12, 2005

If you were out plowing when it stopped working, it seems unlikely that you suddenly had the wrong actuator.

I don't remember that system well and would have to dig up a paper manual when I get back to work, but I'd say the first step is to be sure you're getting power and ground to the actuator when you're in 4WD.

You don't have to take out the transfer case to replace the switch, I remember that much.

jmelrntz · December 12, 2005

how is it that the 3 wire actuator works without the brown wire having anything ran to it? my guess is that its the switch as i'm not getting any power to any of the wires from the truck side of the plug. i'm just wondering if i should switch to the 2 wire actuator while i'm at it? i need this truck to be fully operational, it is what pays the bills.

GM-Tech · December 13, 2005

If I had a schematic in front of me, I could tell you how it all works. Since I don't, I can't. Been too long since I've seen a '92 to be sure of anything.

Trouttrooper · December 13, 2005

We had a lot of problems with that era p/u and it seemed like it always boiled down to that darn thermal regulated acutator. Either getting wet where it shouldn't and shorting out or just plain not getting hot enough to stay engaged. I believe there is a non-thermal replacement which is the way to go. A couple times we had some poor grounding issues.

As for specifics on the wiring, it's been too long since I've crawled under a '92.

Jarv · December 13, 2005

The old style actuators have only two wires. The new style (plastic) have 3 wires that go to the transfer case. Run the new wiring harness to the transfer case and splice in the brown wire that is in the new harness to the brown wire that is coming out of the plug from the transfer case.