I have a 1990 K1500 4X4 Chevy pickup that wont engage into four wheel drive. I bought the truck from a friend who had just replaced the actuator on the front end but that did not cure the problem. The shifter in the truck will put the truck into 4 low and 4 high but the front end does not engage, seems to be an elecrical issue as the console doesn't light up when shifting the transfer case. Is there another solenoid or relay on the transfer case that engages the actuator on the front end?

The actuator will not be on the front differential or drive line, it will be on the transfer case, which is mounted behind the transmission. Follow the front drive shaft back from the front differential, and the component at the rear of the driveshaft is the transfer case. That is where four wheel drive is engaged/disengaged.
I'm not familiar with your vehicle, but if you have a separate lever to engage 4wd, there will not be a fuse for the actuator - it is a manual system. If the 4wd is selected electrically, check that all wiring and connectors on the transfer case are in good condition.

There are 2 models here the push button will flash if the system is not engaging or disengaging properly . If front drive shaft is turning. That is with car raised and supported . if front drive axles do not turn then the axle actuator is not engaging axle shaft passenger side. Remove actuator and manually engage shifting collar with a screwdriver still does not turn then inner axle is twisted.

2002 chevy s10 4 door 4x4 4 wheel drive wont engage

mounted to the tranfer case you will see what looks like a window motor. Round with wires coming out. This is the actuator motor for the four wheel drive. A lot of times if they are not used the brushes will stick in the motor and if they do the four wheel drive will not engage. Sometime you can tap on the motor and it will work. You also will have a fuse for the four wheel drive in your fuse panel. Good luck, hope this helped

the accuator is proby weak and working under pressure!!!!!

The four wheel drive actuator is prolly out. same thing happened to mine.around 75 bucks to fix

Yes it is a 700R4. They went to a 4L60E in 1993. Good Luck

w9fro..In1995, and other model years, the actuator used to engage the transfer case into four wheel drive is oil filled with a heating element.
When you select four wheel drive the element heats up, the oil expands and engages the transfer case. Unfortunately if the actuator fails, the truck remains in four wheel drive. GM has an improved actuator so the problem does not repeat.
As always, check the basics, power, grounds and switch at floor select before replacing the actuator.
Also, if the truck is truly stuck in four wheel drive, you can tell by turning the truck in a tight circle. If the front end wants to "bunny hop" it is definitely engaged.
Best of luck, let me know.
Regards,

I replaced the malfunctioning “thermal actuator” with the “Warn” Vacuum actuator setup, it’s been working great for about 7 years now, simple install, if I remember correctly, it was about $150.
That’s what engages the front diff into 4wd.