This is all related to a Jayco Eagle 283G on a e450 v10 chassis.
Use 5-20w oil or the engine will have timing knock and use oil. Low tension rings is the reason the oil weight has to be kept low. Oil in the combustion chamber lowers the octane.
Blowing #13 fuse in the chassis fuse panel that goes to the ac panel and feeds the blower relay and the temp control(blend module). Under the radio the wiring harness sets on the threaded end of a bolt coming from the engine compartment holding a emission control on. The bolt threads works into the wiring harness and shorts to ground the #13 fuse power feed. My RV has 48,000 miles on it and is a 1999. You have to remove the engine cover to see it, after you do, put something rubber on top of the threads where it's digging into the wiring harness and tape the harness.
I found this problem by cutting a fuse apart the get the spade connector and inserting it in the right side of the fuse spot for #13 fuse and used a ohm meter with alligator clamps . I attached one side to the spade in the fuse block and the other to ground so I could move the harness and find the ground. My meter has a audible tone for continuity. I unplugged the ac control panel and the blend door module I had already tested but I think I could have just turned the selector off and got the same result.
Little or no engine vacuum to the AC controls, (causes blowing out the defrost vents and some on the floor no matter where you put the selector) and blowing out the dash when you are accelerating. Ford says you have to remove the right fender to repair the vacuum accumulator inside the fenderwell and charge over $1000 for the repair. I used a small freon canister and a vacuum check valve to do the repairs. Drill the top and tap a 1/8 npt thread in the empty freon bottle, buy a 1/8" NPT hose fitting for small rubber hose, find the small vacuum tube off the engine that goes to the fender well behind the battery. It's in a plastic tray under the hood at the top. Buy some rubber hose to fit tightly over that tiny tube, cut the tube and make sure you have engine vacuum there, I attached pictures. I used 2 check valves but one would do fine. The line from the fenderwell goes to the ac right above the passenger's seat foot well, run your new line to that same area and attach it with a small hose that fits over it tightly. I painted the freon bottle black and wrapped it in felt using a zip tie to attach it adjacent to the radiator. Your selector switch will now work perfectly do matter the throttle position.
Cruise control not engaging. All 1999's should have had a harness change recall that added a 2 amp fuse at the cruise control actuator under the radiator water bottle under the hood on the right side facing the motor (drivers side). The cruise controls actually got water on a ckt board and caused a fire so ford Added a 2 amp fuse the the ckt. If your cruise doesn't work, remove the water bottle and set it aside, reach your hand down and find the fuse holder attached to the cruise module harness and check that 2 amp plug in fuse.
Front brake caliper seizing. The steering will pulling to the right or left while driving and the stuck brake caliper disk will be hot. 2 bolts hold the caliper on, the problem is , when you get the bolts off, the caliper is stuck to the disk, use a large c-clamp and a socket to push the caliper in to allow removal from the disk. Once off, remove the disk brake pad, push the caliper piston in with the c-clamp. Water causes corrosion between the piston and its housing, it just takes a tiny amount of corrosion to cause the caliper to stick. There is a black seal around the piston housing, use S'OK or Kroll or any corrosion removal product and the small plastic tube they all come with and spray it under the seal lip with the piston all the way in. Work the brake pedal with the engine off allowing the piston to only move about 1/2" and press it back in several times with the c-clamp, (If you push the pedal too much the piston will come out too far and you will lose brake fluid). Put it all back together, worked for me. No more sticking.
Add battery isolator instead of start solenoid. The house battery doesn't charge while the motor is running from the alternator, only while plugged into 110v ac or with the generator running. The Aux. Start button on the dash goes to a solenoid and is only actuated when the button is pushed. This relay connects the chassis battery and the house battery together and prevents the house battery from discharging the battery used to start the engine. Mine had a open coil so it didn't work. I replaced it with a battery isolator that allows the running engine to charge the chassis battery while you drive.
If you don't agree with all this, I understand perfectly.
pictures links:
http://i1114.photobucket.com/albums/...0vac%20mod.jpg
http://i1114.photobucket.com/albums/...dash%20air.jpg
http://i1114.photobucket.com/albums/...0vac%20mod.jpg
http://i1114.photobucket.com/albums/...r%20vacuum.jpg
http://i1114.photobucket.com/albums/...vac%20line.jpg
http://i1114.photobucket.com/albums/...vac%20line.jpg
http://i1114.photobucket.com/albums/...%20harness.jpg
http://i1114.photobucket.com/albums/...123_131915.jpg
http://i1114.photobucket.com/albums/...ator%20mod.jpg