A week or so ago I posted issues I was having with our Suburban furnace and its erratic behavior, and had many helpful suggestions. John Davies requested I post a followup to benefit others who have this furnace should I take it upon myself to repair the thing which I did. It appears to be working fine now. Hopefully other members who still have this furnace will benefit from my experience. Be forewarned though removing and repairing this furnace is nothing short of a major PITA, so much so its hard not to recommend changing over to the Atwood which is now being used in both the Elite II and Elite. Even so you have to get the darn thing out of its compartment, no easy task in itself.
So let the fun begin.
1. The basics: remove cover hatch under the curb side bed, remove everything stored in the basement rear, then the black rubber mats. At this point you will see several white plastic panels that make up a sub floor and partition to the heater compartment. The floor panel closest to the vertical partition will need to be removed, then the vertical portion will need to be moved out of the way. Its size prevents it from being completely removed from the basement area. There are several, 10 or so, phillip's head screws holding these two panels in place.
Tape applied to the edges of all hatches due to abrasive fiberglass. This access looks down onto the furnace casing
This second photo shows the compartment after the plastic boards are removed at the rear of the trailer in the basement. The two circled marks represent the two casing mounting bolts that have to be removed. The red arrow represents yet more melted red tape.
2. Once those panels are removed, you will have much better access to the furnace itself. Turn the gas valve off at the front of the trailer, then burn out the remainder of gas in the line at the stove top. At this point it should be safe to disconnect the gas line as you can see in photos provided. Remove the sheathing on the wiring harness that goes into the side of the casing to the furnace. This will enter from the right side of the casing, facing the rear of the camper. Take a phone picture of the harness making special note of the connections. The two blue wires are for the thermostat, but notice the ++++ will be unconnected, while the neutral is connected to a pink 18 AWG thermo wire. The other red thermo wire is also not connected. Do NOT connect the red to the ++++ blue wire during reassembly. The other two of the 4 wire harness will be red and yellow to the furnace and yellow striped and brown for the Oliver wiring. Yellow to yellow, red to brown when reassembling. At this point after photos are taken cut all wires, but you should shut off all power to the camper before doing so. I was careless and blew a 10 amp fuse to the furnace when stripping the wires again for re-connection a couple of days later. I would encourage anyone who has gotten this far to reassemble the wiring using insulated fast tab connectors so that you don't have to continue cutting these wires in the future, thereby shortening them during another service visit, which hopefully you'll never have to do. From the factory mine came connected with crimped connectors.
Clear view of gas line disconnected from brass nipple, note red arrow pointing to wiring harness
Removing one of the casing mounting bolts, red arrow points to the 90 degree brass nipple that will need to be removed
Mounting bolt on right side unscrewed, circle around left mounting bolt, also notice yet more red tape, circle in the upper right is the one to dislodge the heat exchanger system from the casing.
Wiring harness as attached to the Oliver.
3. Remove the two set screws at the rear of the furnace casing. John Davies pointed this out in a previous thread. At this point you will have a decision to make. Try to remove the furnace from the casing while allowing the casing to stay in place, or remove the entire enchilada at once. Neither choice has a happy outcome. Should you try to remove the furnace from the casing, the brass 90 degree nipple will also have to be removed first to clear the casing. Red arrow points to this in photos. There is one set screw that holds the heat exchanger within the casing and can be found at the bottom of a small sheet metal panel that holds the circuit board in place. The gas line runs through this panel which has some info regarding the specs of the furnace. If this doesn't work, then the entire casing assembly has to come out which is what I had to do. This presented another almost overwhelming conundrum as you will see in the photos. At the rear base of the casing there are two medium size set screws or self taping bolts. Remove those, and if you are lucky the whole thing should just slide out. I wasn't because who ever assembled and installed this furnace on our Oliver also installed one of those self taping bolts to the front of the casing bottom completely out of sight and completely inaccessible. I'm not making this up. Suburban only requires two bolts to be mounted at the back, where the access panel is located.
Close up of bolt attaching casing to the outside edge. This is the one which was totally inaccessible and had to cut.
Furnace mounting frame made by Oliver that attaches to the carriage frame of trailer. Its obvious I was not able to cut the bolt but rather the sheet metal casing and then pried the casing away from the bolt. Arrow points to yet more tape debris.
Looking down into the torn mounting bolt hole of the casing.
Another view of the cut casing from below
4. Assuming you have a front mounted casing bolt, it gets ugly here. You will either have to cut the bolt from underneath or cut into the casing and pry the thing off which is what I did. So with rear bolts and front bolt removed, gas lines disconnected and wiring harness cut it should be fairly easy to slide the assembly out of the compartment, but it is a tight fit and will need to be shifted sideways while pulling backwards to clear the Oliver compartment area.
Using my multi tool saw to cut bolt/casing. This was extremely difficult access with very little room to move let alone apply force.
5. After removal there were a few disturbing factors I had to deal with. One the frame work the furnace is mounted to was extremely loose and wobbled back and forth like a seesaw because the installer was too lazy to finishing driving the bolts completely down snug to the Oliver carriage frame. No they did not vibrate loose, the bolts were way too tight to ratchet down. As you can see in the photos those bolts were 1/4 inch to 3/8 of an inch above the mounting frame. But thats not all. Once I had the assembly out of the camper, and pulled the heat exchanger from the casing I found significant amounts of some sort of red tape all over the inside of the casing. The tape was similar to electrical tape only red but most of it had been completely burned onto the heat exchanger and other parts or was wrapped up around the fan assembly and the shaft going into the motor. Again I'm to making this up. At this point I started noticing shreds of this red tape debris laying around parts of the furnace compartment area as well. Thankfully there was no damage to the sail switch to the best of my knowledge.
The next two shots are the loose mounting bolts that attach the furnace frame to the actual Oliver frame. This illustrates the extent of unfinished work.
The next two shots show red tape bound up on the fan and shaft to the motor.
6. At this point I figured I better inspect the ignitor and unscrewed it from the rear of the heat exchanger it looked ok other than some carbon deposits but I started noticing the center pin rotated about 15 or so degrees which would change the tolerance. Called the local RV dealer and luckily they had replacements, but didn't realize until back home and reinstalling the gasket was disintegrating. Back to the RV dealer to buy a gasket kit for the ignitor and furnace door. At this point reassembly was pretty much academic. But before installing the casing assembly I ratcheted down those bolts that hold the furnace frame onto the Oliver carriage frame so the entire assembly was rock solid once complete.
7. The brass 90 nipple should be reinstalled with gas pipe dope, but the fitting to the gas line does not require this as its a compression fitting. Make sure all fast tabs connectors for the wiring harness are crimped like a cold weld. Note: not all crimpers have the ability. Once everything is properly hooked up, turn the gas valve back on. Wait awhile and look or smell for leaks, better yet use a propane sniffer if you have one. I don't. My gas line connections appeared to be good so at this point it was time to fire things up, but it was 90 degrees outside. I would have to wait until the next morning for cooler weather. Thus far its been working fine since reassembly.
View of the sail switch from above, which is mounted in the upper left corner of the casing assembly so that the fan blows on it.
Attaching screws to the basement subfloor made of plastic sheeting, red circles represent the screws.
Let me know if you have questions, be glad to answer what I can.