My 4x4 does not work properly.

If I start the vehicle, I stand a 25% chance of when I hit 4x4 it will go into 4x4 mode. Once in 4x4 mode it will run, however, after a while (especially if I stop then continue) I get periodic clunking coming from under the engine.

Once in 4x4, it's hard to get out of 4x4. Usually requires a stop and several pushes of the button. I have to stop cuz if I don't, I will eventually get a grinding noise. The same applies (grinding and a stop) if I'm in 2wd and try pushing the button several times for 4x4. When the button is pressed, the light will blink a couple times, you can hear a double clicking noise then it reverts back to the mode it was in.

Only other issues is the turn signal (which I read up on here and will clean) and no heat.

I read about replacing the module, but at no point does all 3 lights come on at the same time. Any help gratefully appreciated.

LESTER
This actuator is located under the battery tray on the passenger side of the engine compartment.

How do I access? Remove the battery? What are the dimensions of the actuator?