Review on Standard Motor Products TCA21 Switch by Ben Cooper

If you replace the truck adapter harness with a slightly newer year plug (eg '96) you can plug it directly into this 4WD activation switch and leave this part intact and it will work, it's just a fork difference. I built a desktop 12V AC/DC converter so I knew my first switch was stuck and not working. This device ran from the converter and then into the truck - no problem. The function of the four-wheel drive system has been restored. I'll see how long it lasts but other than that I recommend it.