running hot, no fans

Wondering if anyone can point me in some direction...
• I know it's not a precise instrument, but my dashboard temp gauge has always topped out pointing at the left edge of the middle line, maybe up to dead center on long hills. But recently it’s climbing past normal during flat, easy driving. I haven’t let the gauge get up to the first line above the middle. I removed my foam grill block right away, still happening.
• I haven’t gotten any warning lights for temp or CEL.
• The radiator fans don’t come on when it gets that hot, but they have come on in the past without the dash gauge reading this high. And the fans do come on when I turn on the AC. So at least they work then.
• I can see the coolant circulating in the expansion ball when I open it (cold).
Sounds like the coolant temp sensor sends a separate signal to the dash and the ECU. Does the reading to the ECU trigger the radiator fans? Could that have failed separately from the dash sensor?
Thanks for any input!

If memory serves, there is a radiator temp switch on the radiator itself that triggers fans based on coolant temp at the radiator. There is a high and low, you can jump the wires at the switch connector to see if the fans work as they should.

The temp gage on mk3's is rubbish and can’t be trusted for anything. You need a real temp gauge. I think there is a way to tune that gauge with VCDS so it’s more precise but I’m not sure about that. I think I read it in passing but never read up on it or did it.
If I remember right, the ECU gets all the signals and then sends it to your dash. I’m 99% on that one. Otherwise scangauge II would not pick up that value. Underneath the coolant tank is a black box with a 20 amp fuse with a clear door on it. If that door is missing or leaking, they do, or just randomly, that will fail. It is the fan control relay box and it’s a $150 part and you can’t get the cheap version of it, only the OEM works, trust me on this. Anyways, tap it with a wrench when it’s hot and if your fans kick on, it’s dead and needs replacing. The AC fans get a command right from the dash to turn on though that box but usually that’s not the part that fails. If you’re just running hot due to the fans not running, this is probably your issue. You can hard wire up the fans for a bit and go for a drive and see if it still gets too hot. you might have a separate issue, thermostat, head gasket lift, other causes like a failing pump or a leak or something. Hard to tell what your problem is without a bit of trouble shooting.

the change on your temp gauge seems needed to be traced down. usually cooling system work should help/ perhaps straighten out. when was the last time you serviced cooling system.
as far as the rad fans. 1 having them work when using a/c a+. 2, im not 100% sure but on the older models look down on the bottom of radiator, for the older models sensor is on battery side(of rad), ?Q?(question that is<)swap out that sensor? not hard to do. used to take a cheesy fabric type o-ring,gasket. find the better type gasket, if you do, id recommend. i havent had to look where that sensor is on my 'newer' cars by now not very new at all. havent had that type of cooling problem. 3, make sure that rad sensor is working. other than that on these cars little extra heat in the dash sensor is not going to be a problem, at least like that. but so again check out your cooling system before long. id suggest.
another thing. check in radiator fins, if you use a soft cover, or like you said a foam cover, foam can deteriorate and get into fins. if you have to clean do so carefully. do want you to need to replace radiator like this.