Last year my 4wd wouldnt work, when I went to engage it, both hi and low would blink constantly, and wouldnt go off till I killed the ignition. I Found out it was the dash switch. Replaced it and boom, good for the year.

Now I have a similar issue, but its very odd.

I went to use the 4wd and nothing, both lights blinked aout 6-8 times, then went off, no selenoid noise or anything. So I kinda dismissed it for a while, busy at work and no free time to diagnose.

Then I had to replace the battery and had some spare time to go ahead and see if I couldnt find the problem. Checked all fuses, pulled the switch and cleaned with electrical clener, put it back together, started the truck, Woot! problem solved!!! Engages into hi and low when parked in neutral.

Decided to do a road test, went down the road tried to switch on the fly to 4 hi....Problem is back.....

Disconnected then reconnected the battery, once again everything works great while shifting to either from a dead stop! As soonas I try to shift on the fly into 4 hi then it reverts back to not engaging and lights blinking, no selenoid noise. Disconnect/reconnect the battery and it works again.

So the switch is fine, shift motor appears to be fine, fuses are all good...
Would this be the control module?

In the winter here in Colorado I really need that shift on the fly to be working...

99 ranger
4x4
4.0
stock hubs

 

that would be the vacuum engagement hubs that are failing

rugged ridge makes a set of manual hubs that you can install yourself

 

Okay, IF it is the hubs failing, and I change em to manuals, I have one question...

Mornin comes, its spotty to bad - Bare/Slush/snow/ice, I got 50 Mile commute to go, I just lock em in the driveway and go, then use 4 hi (shift on the fly) as I need as usual?

 

yes , just lock the front hubs and be on your way

most people just lock them in for the entire winter season

i would not . it just adds more wear and tear on the front driveline than there needs to be