Cooling fans not coming on.

Long story short i got stuck in some traffic on my way home and my temp gauge started to creep up until I turned on my AC to kick the fan on. I was doing some diag on it tonight and when I turn the key on the passenger side main fan turns on but the drivers side aux fan does not. Also as the temp gauge starts to climb my fans will not come on at all, only when I turn on the ac. My first thought is the coolant temp sensor. I’ve had zero luck with any after market brands for them and I can’t source a ford part. Any ideas?

Edit: when I have time this weekend I plan to go through the basics like jumping the coolant temp connector and seeing if the coolant hose on the bottom of the intake is clogged.

Driver one only turns on when the temp gets to 220

Passenger side turns on at 210 or when A/C is on

Here's an article to test the fans:
https://turbotbird.com/thread-cooling-fan-test

Found my original temp sensor I took out a few years back and slapped it in. Works perfectly. Needle hits the half way point and the fan kicks on. Just amazes me a company can’t make a reliable replacement for such a simple sensor.

I also use a Ford part for this temp sensor I get out of a 5.0 in the junkyard. Also, that passage tends to get clogged up real bad and the coolant doesn't floe over the sensor. Mine was real bad and had to use a drill to clean it out.

Found my original temp sensor I took out a few years back and slapped it in. Works perfectly. Needle hits the half way point and the fan kicks on. Just amazes me a company can’t make a reliable replacement for such a simple sensor.

Yeah when I replaced the head gasket in 2011 I decided since I already had half the engine apart I would replace the various coolant hoses and things like the temp sensor, that are really difficult to get to otherwise. On the test drive my new temp sensor sent the needle almost to the top of the gauge. This kind of freaked me out, as I didn't know if there was now an internal problem after reassembling the engine. When I got home, driving very slowly, I replaced it with the original. Gauge was back to normal; so I went out and got temp sensors from various parts stores, and tested them in a pan of water that I gradually increased the temperature to boiling, then 220 degrees. The current readings were all over the place--some had "hot" resistance at 220; some at 210, etc.

It does seem like such a simple thing. I blame it on a "universal" one designed to work in as many cars as possible.

My temperature needle sits at the top of the gauge, right over the N. I have measured the water outlet with an infra-red thermometer and determined that the engine is at about 210 with the needle there and there's really no problem, aside from the sense of unease you get looking at it. It seems like the sending units for the gauge are just inconsistent.