Bert,
I usually do most headlights at 260°F for about 13 minutes, that usually is right to get everything warm enough. Couple tips. The headlight is going to be hot. You are going to want some Mechanix gloves, or something similar to be able to handle it, so that you can open it quickly. You don't want to wait too long, because the sealant will start to harden. Be aware of all clips and screws BEFORE you put the headlight in the oven. You don't want to have to waste time heating everything up to find out that there is a screw holding the lens on. Also, when prying to get the lens off, be careful, the back housing is also going to be warm, you can tear, crack or warp it if you force it too much.
I usually do most headlights at 260°F for about 13 minutes, that usually is right to get everything warm enough. Couple tips. The headlight is going to be hot. You are going to want some Mechanix gloves, or something similar to be able to handle it, so that you can open it quickly. You don't want to wait too long, because the sealant will start to harden. Be aware of all clips and screws BEFORE you put the headlight in the oven. You don't want to have to waste time heating everything up to find out that there is a screw holding the lens on. Also, when prying to get the lens off, be careful, the back housing is also going to be warm, you can tear, crack or warp it if you force it too much.