Four wheel drive has not worked in a long time

1993 CHEVROLET BLAZER
195,000 MILES • 5.7L • V8 • 4WD • AUTOMATIC
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SNOSAINT
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This is my elderly parents vehicle. Four wheel drive has not worked in a long time. They are away on a trip and left it with me to do brakes exhaust and more. Putting it in Four wheel drive should light the indicator, engage the transfer case and the front wheels. Indicator not lighting, transfer case engages (i think) because the front driveshaft is locked, not free but the front wheels are not driven.
Suspected the actuator (i think it is just a solenoid), so we took it out. used a test light and it is getting power. We were able, with effort and tools able to pull pot and push in the plunger, so we lubes it with some penetrant and worked it a bit. We plugged it in with out installing in the axle, and when put in four wheel drive it slowly pushes out with almost no force. i think we can push it back in while actuated. I am wondering if that is supposed to work that way or not. I also noted it gets very warm when actuated.
Aug 22, 2017 at 3:34 AM
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HARRY P
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There is a vacuum controlled actuator under the battery tray for the front wheels. Take it out and inspect it for leaks. Also inspect the vacuum line running to it. It is a very common problem with Blazers. If it is the problem, you will be able to unhook the cable, engage the four wheel drive, and pull that cable and lock it with vice grips. Then test it to see if the four wheel drive is working.

Good luck and let us know.
May 14, 2021 at 5:30 AM
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SNOSAINT
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I do not believe that vacuum actuator applies to the 1993 full size Blazer. This has an electric actuator from everything i have read.
May 14, 2021 at 5:30 AM
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HARRY P
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Sorry my mistake. I was thinking of the S-10 Blazers and got ahead of myself. From what I am reading go ahead and replace that actuator/solenoid. It should not be that easy to move or get hot like that. There is a way to test resistance in it but there is not indication of what it should be. The fact that it gets hot just being turned on is a sign that there is too much resistance though.
May 14, 2021 at 5:30 AM
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STEVE W.
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That should have the wax pellet style actuator. Those work like a thermostat. There is a heating element that causes the wax to expand and move the actuator fork which locks the two pieces of the axle together.
They do not have a lot of force but when the wax is heated they should not be easy to push back in. There is a conversion to the newer motor style unit for that axle. Much better than the wax pellet style as it locks/unlocks faster and doesn't act up in the cold either.

When you either pull the lever or push the button, that switches the power on to the front axle actuator. It should expand and lock the axle in two to three seconds if it is working properly. When they are new they work okay, when they get a few years on them, not so good.

On the push button four wheel drive select units the front axle switch engagement tells the TCCM when it is engaged and that it can now shift the T-Case into four wheel drive.

I would replace/upgrade the actuator.
May 14, 2021 at 5:30 AM
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