'79 GE Oven temp about 100 lower than set temp.

SOURCE: Faulty bake or broil element

The solution to this problem depends on whether the oven is electric or gas. Electric oven. If your electric oven's bake or broil element isn't working properly, either it isn't receiving electric power or the element or the oven control may need to be replaced. In many cases, the wiring to the elements can be burnt or broken. 1) Be sure the controls are set on the proper setting. 2) Be sure the stove is plugged in and/or check the circuit breaker or fuse that serves that circuit. 3) Call an appliance repairperson or replace the element yourself as follows. 4) Unplug the oven and let any hot parts cool. 5) Unscrew the mounting screws that secure the element bracket to the oven and pull out the element far enough to access its terminals. Note which wires are attached to each of the terminals, then disconnect the wires (pull off the wire clips or unscrew the wires). 6) Take the element to a parts dealer, along with your oven's model and serial number, and buy a replacement (preferably the manufacturer's suggested replacement part). 7) Reverse the process to reinstall. Gas oven. When a gas oven doesn't get hot, it generally means that it isn't receiving gas, the gas valve isn't distributing gas to the oven burner, or the ignition system -- either an electronic ignition or pilot light -- isn't working properly. A common problem with ovens that have a pilot light is that the pilot light has gone out. NOTE: Gas ranges younger than 10 years old have a sophisticated fault code system that governs their ignition. Always call an approved warranty service provider to handle problems with these ranges. Here's how to troubleshoot your range: 1) Be sure the controls are set on the proper setting. 2) Be sure the stove is plugged in and/or check the circuit breaker or fuse that serves that circuit. 3) Check the gas valve to be sure the gas supply is turned on (also make sure the house's main gas valve is turned on). 4) On a stove with a pilot light, make sure the pilot light is burning. If it isn't, re-light as discussed HERE, or in your owner's manual. 5) Adjust the pilot flame (older stoves only). 6) Turn off the gas and unplug the stove (or turn off its circuit at the electrical panel). 7) Clean out the oven burner ports, using a stiff wire. 8) Plug in the stove (or turn on its circuit) and turn the gas back on. Re-light the pilot (if it has one). 9) If the oven still doesn't work, call an appliance repairperson.

SOURCE: Bake element does not heat

After removing the racks, rack rails and the back plate I removed the 2 screws the hold the bake element. Lifting the front of the bake element up and carefully pulling the element out and gently moving the element so the connector clear the hole I was able to disconnect the wire. After testing for continuity with an ohm meter (non found) I determined the element need to be replaced. $37 and 45 minutes total.

SOURCE: GE JTP 1580W288 Set oven to Bake, switches to broil at bake temp

The F2 Error code means the oven has detected an excess temperature condition. Most often this is due to a bad temperature sensor - the sensor costs about $75 from an online repair site. 
How to remove and replace the temperature sensor. In most GE ovens, when you open the door, you'll see the rod-shaped temperature sensor sticking out of the back wall at the upper left. It's about six inches long and a bit more than 1/8" in diameter, held in place with two screws. 

Turn off the circuit breaker (built-in ovens) or unplug the range before attempting the replacement. 

The replacement sensor will come with instructions, but basically it's a matter of removing the sensor, pulling out the wires to where they are connected and disconnecting them. You may have to snip. The replacement sensor will come with high-temp wire nuts to hold the new connection. Polarity doesn't matter; it's a straight resistance thermocouple. Hook it up, be sure you poke the connections back far enough so that they're on the other side of the thermal insulation and not resting against the back of the oven. 

If you continue getting the F2 error after replacing the sensor, then the problem is likely in the control module - this is the circuit board behind the keypad and clock. 

You'll need to remove the decorative bezel to get behind the control panel. Remove screws and set off parts in order - it's not complicated. Once the bezel is off there are two more screws that hold the panel in place. Then you can lift the panel up about a half inch and pivot it forward toward you. You'll see a bunch of wires going to a circuit board. 

On the panel you will notice some black plastic boxes that say "Potter & Brumfield" on them. These are relays. Check the relays - slide the black plastic cover straight up to expose the coil and the contacts. The coil, when energized, closes the contacts - look at all the relays. You can manually close the contacts with your finger (be gentle). If the contacts of one of them are stuck, they might be welded together. You can fix the problem by prying apart the welded contacts gently with a knife blade. Take some time to gently polish the relay contacts with a folded bit of fine grain sandpaper - this will get some more life out of them. Be gentle and careful - the relays aren't complicated but if you bend the contact or rip it out, you'll have to replace the controller, which will set you back a couple hundred dollars. If you unstick and burnish the relays, they will probably eventually weld together again as the rough spot will spark, but when you burnish them with sandpaper they should be good for some more life before they need to be replaced. 

If the problem isn't the temp sensor or welded relay contacts then the problem is obviously somewhere else, but temp sensor and relay contacts will account for the lion's share of F2 errors. 

Once again, be safe, be careful, be gentle. Ovens are not very complicated and they're tough, but always exercise care. Always disconnect electricity before messing with them.
good luck,

SOURCE: frigidaire wall oven will not heat up very fast

The clock control has a relay that turns on the element. It could be failed and would require a new clock control.

SOURCE: The elements will not heat up on bake.

The problem is the Bake heating element. This is easy to check and usually inexpensive. There is a video at www.appliancehelponline.com/servicemanual.html that will walk you thru testing and replacing. It may be a different model but the testing and replacement will be the same. You can also enter your model # for diagrams and illustrations of your specific model. All parts come with installation instructions. Not all models are available.

Testimonial: "Thank you so much. I thought when the oven was on bake that both top and bottom elements worked. I will now go check my bake element."