I STRONGLY feel the safest place for a child in a class C motor home is in the passenger seat......NOT anywhere in the house because the Ford cab is designed with consideration to crash-integrity. The house is not. Cabinetry and contents will injure house occupants.
Seating the child in the passenger seat also makes for a much more pleasant trip. They see so much more sitting there, and your conversation with them and pointing out things to them is priceless.
Assuming a 1998 E-Series has a passenger-side air bag, I also agree that you need to disable it to seat a child there. The first place to look is in your 1998 E-Series owners manual. If there is no mention of disabling the air bag (I think there is no provision for 1998 model year) then you need to resort to plan-B......unplug the passenger air bag by hand. Look up from bellow for the connector and simply unplug it. Hopefully it is reachable without too much disassembly.
But BEFORE unplugging the passenger air bag, FIRST disconnect both your chassis battery and house battery and wait an hour before attempting it. I include the house battery in-case there happens to be a back-voltage present. Waiting the hour allows time for capacitor-held power to drain. Then it is very safe to unplug the passenger air bag.
The actual wait time in most vehicles is one minute, but being a 1998 motor home, just wait an hour to play it safest.
