If you find the relay solenoid look to see if it has cables on both sides of the big posts or a cable going from one to the other. See if there is power or not to the switch and then at the solenoid.

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Battery disconnect switch problems. Brown 5 amp blade fuses. Personally id just disconnect the battery and leave it be. This not only disconnects the battery when they get charged but also provides a jump start for the engine battery in the case of a motorhome. The hyundais i owned over the years had a transit switch on the under dash fuse box that would basically put the car into hibernation but my car never sat long enough to need it turned on. This may be a loose wire. Two on each one as a rule.
It prevents your battery from going dead by automatically disconnecting the battery at 120 volts therefore reserving enough power to start the vehicle. Check the fuses on the solenoid itself. If you have a battery disconnect switch you probably have a battery isolation manager or bim that is usually located in the battery compartment. The disconnect system is a mh builders installed item so the chassis wiring will be of little help. Once you find out if the problem is in the switch or not then we can check the solenoid itself. You need the mh info to locate it.
Automatically disconnects the vehicles battery at 120 volts. A state of the art battery disconnect switch device automatically monitors your battery capacity. A battery will last a damn long time when its not being drawn from. Disconnecting or replacing a battery on a computer equipped vehicle may cause starting driveability and a number of other problems including loss of air conditioning power accessory functions door windows seats sunroof false warning lights even damage to certain electronic modules.