I have them in several location on my 2005 8377. The majority are located in the front driver side compartment where most of the large DC fuses and relays are. The chassis has a fuse and relay box in front engine compartment and under the dash in driver foot well, but none of those should be related to slides getting power. Lastly, for mine I have fuse/breaker panels DC and AC built into bed box. Depending which slides and how they are powered you could be looking for multiple fuses. For example, if they are hydrallic slides, then checking the pump fuse is required. You also will need to make sure you coach power disconnect is working properly. If the disconnect is "disconnected" then your slides won't work. Also, in my coach, my driver and passenger seats must be fully moved forward as to not interfere with the slides. There is a sensor in the seats to ensure this is done. If not, by slides will not move....if this is faulty that could be the cause.