Thermostat replacement

Name brand parts cost more in part because they have advertising to pay for. They also want to recoup the cost of development. Some companies just buy parts from the the original manufacturer and rebox them under their own name. (That's why NAPA fuel pumps are just as quiet as Chrysler pumps. They both come from the same supplier). Echlin usually costs more just as name brand canned vegetables cost more at the grocery store than the store brands.

There might not be any difference. They could all have come from the same factory.

That's what I'd go with.

Wrench.

Here's a photo from rockauto. Com.

If that's just an on-off switch, chances are it's not monitored by the Engine Computer so it won't turn on the Check Engine light. It depends on whether the switch turns on the fan motor, or the switch signals the computer to turn on a relay to turn on the fan. Common sense vs. The way things are typically done with over-engineering.

If the part is a temperature sensor, it is going to provide a voltage signal to the computer. The computer will turn on the fan relay when a certain voltage is reached. That type of sensor is monitored, and when you unplug it, the computer won't know engine temperature so it will turn on the fan just in case the engine is overheating.

You didn't fix anything inside the sensor by unplugging it. The fact the fan turned on when you played with the plug suggests it wasn't making good contact, either due to corrosion on the terminals or a terminal is stretched. I'd look closer at that plug.

Here are the cooling fan schematics.

Unplug the fan switch connector and use a jumper across the terminals, does the radiator fan come on?