No, that sound like you just didn't get the engine hot enough. The other fan switch (upper-radiator-hose nozzle at the head) has a different setpoint, but it only has authority to run the fans after you turn off the engine.

First check the circuits & relays like this...
- Unplug the fan switch located in the thermostat housing (lower radiator hose)
- Jumper the 2 wires together with a paperclip
- Key ON, that should make both fans run
- If that's OK then put the wire back on & continue

Maybe your thermostat is allowing the temperature to get a bit higher, or maybe your temperature gauge simply reads a bit high. (not the most accurate instrument) Some people have compared it against an IR temperature measuring gun pointed at the upper radiator hose.

Put a blanket over the grille & let the engine idle for awhile. Watch the gauge & be prepared to remove the blanket & turn on your interior heat & blower to get the temperature down.

A better way to test that fan switch is to remove it & put it in a pot of hot water along with a thermometer. Use a multimeter in "continuity" mode and heat the water on the stove. There's a specification for what temperature the switch should close, you should probably search for that or look in a repair manual. This method spills coolant or you have to try to plug the hole or something like that.

 

The mechanic thinks that it may be the after-market temperature sensor (the one that gives info about whether the fan should come on after shut down) that I replaced the faulty one with.

I did do the test you mention and both fans work.

I think I will just keep an eye on things and try to bleed any extra air out. Unfortunately the mechanic didn't realize there was a bleeder at the thermostat.

 

Hi Dondrop, had similar issues with my 93 ex after pretty much replacing or testing every component in the cooling system, fixing or replacing non functioning parts I had the same problem. when stopped the heat gauge would climb all the way up to the red. after several drive and turn off cycles I noticed that the gauge would stay at the normal setting longer each time. after 2 weeks of driving the car for short hops 2 or 3 times a day the problem has finally gone away. It seams that each time I replaced a component that involved fluid loss the problem would return. Even though I followed the procedure for bleeding the cooling system each time it seems that even a small amount of air trapped in the system will cause the sender to peg to the red zone. My car has just under 200,000 kilometers on it and as far as I know has the original water pump. It may be that the old pump doesn't quite have enough power to push all the air out of the system? So my advice is drive your car through several start/stop cool down cycles and see if the problem persists or changes at all.

 

Did you bleed the system of air as shown in the video below? Even if you crack the bleed valve on the thermostat housing, you still need to bleed/burp the system as is done in the video.