About two to three months ago, I started receiving the F-1 error on my oven. After about two days the intermittent error ceased. A few weeks later I began noticing that the oven would not heat up to the temperature requested. Now, it is unable to heat up on it's own. However, I can turn on the broiler and heat the temperature up to the desired degree and then switch it over to an oven setting. As my items are cooking it obviously looses the tempurature, but it's been getting the job done. How can I find out what I need to replace to get the oven back to normal usage?

Thank you