Review on Dorman 600-400 4WD Locking Hub Solenoid for Ford / Lincoln Models by Carlos Burrows

Bought it from Revain, installed it, drove around the block and loved it. But then I thought it's worth checking again - I connected a vacuum gauge to the outlet and you know what? It didn't turn on or off when I flipped the 2WD/AWD switch. He never let the vacuum flow. I checked the voltage and turned the voltage on and off correctly, but the vacuum never got through. The only way to leak vacuum was to disconnect the vacuum line, then apply power, then reconnect the vacuum line in that order. Then the vacuum will go. But if I then remove the voltage and then reapply voltage, the vacuum doesn't come back. So I knew there was an electrical connection. But it looks like the magneto only had half the power needed and was negligible depending on whether it would work or not (only works if it can start without vacuum). Thinking mine was just a bad one, I bought a second one - at the time from my local parts store (instead of Revain). It was the same Dorman brand and part number. Result: Identical! It had the same when not activated unless you manually connected things in a specific order (which never happens in the real world). I then went to a Ford dealership and bought an OEM replacement. It was more than double the price. Connected, works great. I could make the vacuum gauge go up and down like a clock just by toggling the 2WD/AWD switch back and forth (to do this just connect the electrical connector and the bottom vacuum line. Then connect the vacuum gauge the upper connection to the solenoid). Crazy that two of Dorman's two parts were bad. I wonder how many people drive one of these that is constantly stuck in the off position (constantly engaging the front wheels) because that's where I would be if I didn't check the vacuum after installation. The only thing that makes sense is that they either don't test them or their testing process is imperfect and has a weak vacuum.