Oven is set at 350 and the temperature will not go up.

Replace oven temperature sensor

350 will be the design max for your oven unless the handbook says for your model is higher rated and is faulty
repair or replace with a higher rated temp oven

Good Morning Friend,

I understand that your Frigidaire oven will not heat to temperature if you set it to 350 degrees. I see that you have to set it to 450 degrees for it to heat up, and then turn it back down to the desired temperature. Please try resetting your appliance, by either unplugging it or shutting the power off at your home's circuit breaker, for 3-5 minutes. Restore power, set the clock and try setting the temperature to 350 degrees. I ask that you please follow up with a comment on the post, at your convenience, to advise if further troubleshooting is needed or if your appliances status has changed successfully. Hope this is helpful.

-Best Regards-
WP

if it is an electronic timer temp controller you might want to check it

Typically an oven beeps when the interior temperature macthes the temperature where you set the dial. This is an audible signal to that fact and particularly helpful when you need to pre-heat the oven. For example it you want to cook something at 350 degrees, you set the dial at 350. When your oven reaches that temperature it beeps to let you know. Some cooking directions tell you to preheat your oven. In that case, when you set the dial to 350 and wait for the beep...you know you are safe to start your cooking process because the oven is now pre-heated to the temperature you set. If your recipe requires a pre-heated oven, and you don't wait for the beep, your taking a guess at what temperature you're cooking your food. Additionally, if you want to know what the internal temperature of oven is and your oven is heated...you simply turn you dial setting and listen for the beep. Again, if you set your oven at 350 and you want to know how hot your oven is... slowly turn the dial setting. If the oven beeps at 275 then that's how hot your oven has gotten. To let it finish heating to 350 just reset the dial and wait for the beep.

Hello....Go and get yourself an oven thermometer form a store like Target.Ther are accurate from 100 to 650 degrees and can either sit on, or hang from your oven rack...Then you can be sure...I hope this was helpful....PEACE....

The temperature is within manufactures specifications.
By that I mean that the majority of manufactures allow a tolerance of + or - 10 % of the set temperature.
So, in your case, 10% of 350 degrees is 35 degrees, thereby showing that the actual temperature you are obtaining is well within the 10% allowance.
I hope this helps you .

From the symptons you describe, I would say that the oven thermostat is faulty, and in need of replacement.
Make sure your thermometer is o/k by checking it against another one, or boil some water, and check the temp of the boiling water, this should determine if your thermometer is o/k.
Hope this helps.

change temp control

The 350 as you stated is a default set point that you see before you start the cycle. What you should see afterwards (start bake) is the current temperature - which would normally be lower than the set or desired temperature - it will eventually get there

Regards