My Ender 3 Pro is not comming up to temp

I started having issues with prints failing and noticed that when the printer was off, it was showing over 100c. (in an unheated shop) The bed was about where it should be. So I replaced the H/E thermistor (and cartridge - just for good measure) and now it shows the correct temp when cold, but trying to print PLA + @ 220c is not getting hot enough to print. It shows 220 on the screen but it can get the filament to extrude (as if not enough heat). The screen shows 220, but clearly wrong. I tried with known good filament and new filament with no better luck. I cranked it up to 260 and the tip never showed more than 190c (with a crappy gun type thermometer - the only thing I’ve got. ) The thermometer seems to read known temps reasonably well (+/- 5 degrees). Any ideas about what I should look at next?

Thanks in advance