Sportsman Cabinet Incubator 1502 Fan Troubleshooting

[OkanaganPeppers]

needing some insight on the sportsman cabinet incubator 1502 this model is an older model from about 2006. Should the fan run all the time? (I can't remember) and when it does run it shuts off way before the desired temperature. I even turned off the heat and then 20 minutes later the fan kicked in? The wires look good and very clean on the inside. I'd like to buy the parts to fix it I'm just not sure if it's the fan that needs to be replaced or what..... any insight be be appreciated.