These removal instructions were original created by battchief i have modified slightly to account for the changes i encountered from the originals i know that many would have some changes
Here’s a step by step (best I can remember!) on how to replace your heater core in a 2001 Itasca Horizon. I’m sure the steps would be the same for most of the same body style coaches, 2000 and up, but some things could be different. I did try to replace the nipples on the old one, but that didn’t stop the leak. It appears to me my leak in my old core was at a tank on the nipple end, but haven’t had it tested yet. The new one is in, and no leaks yet!
A little caveat, I didn’t remove the front end completely. I think it probably save quite a bit of time, because it wasn’t necessary to disconnect all the lights and most other things. I did take the front end and tilt it down, resting it on a trim stool I use to use doing woodwork. In the end, I think I could have loosened the main frame bolts and just tilted it a little and had plenty of room to remove the core. You know what they say, hindsight is 20/20…..
I began by removing the windshield trim pieces on the side. It’s necessary to do this to get to the screw holding the bottom piece of trim of the windshield on each side. I then removed the black trim at the bottom of the windshield. It is presses into a grooved piece, and is held on with glue strips on the windshield and the body. I had a piece left over from when they replaced my windshield, and used it as the glue strips on the old one was bad.
I then removed the trim pieces on the sides. There is a screw at the top and bottom holding a rubber piece of trim, which is also held on with double stick tape. Remove the rubber strip, and there are several screws about 4″ apart holding the trim on. The trim also has a rubbery caulk holding it on. Carefully pry the trim off, taking extra care not to bend it. It is aluminum, and will bend easily. Once the trim is off, there is one screw on each side holding the fiberglass to a metal piece underneath. On the driver’s side, open the compartment door and remove the 4 screws at the L brackets holding the bottom of the front end.
Next, remove the passenger side mirror. From the generator compartment door, disconnect the wire from the mirror. There is a harness just behind the mirror which has pinch clip to keep it together. Pinch these together and disconnect the plug. Remove the 4 plugs on the front of the mirror base. They just snap in. Using a T40 torx driver ( I used one on a 3/8 ratchet.) remove the 4 screws holding the mirror on. On mine, it was necessary to pull gently on the mirror to remove, because the gasket was stuck. It came off without tearing the gasket. Once the mirror is off, use a 3/8 socket to remove the self tapping screws holding the mirror brackets to the frame. Mine had 4 screws.
Removing the windshield wipers is optional. I didn’t remove mine, and broke one. If you choose not to remove them, be sure to put them in the up position before tilting the front end. Be patient, because we’re not quite there yet!
Now time to open the generator door and begin inside. Disconnect the wiper linkage from the wiper motor. It is directly above the generator door inside. I used a large crescent wrench to hold the arm and a ½” wrench to remove the nut. The linkage is easier to remove and reinstall if the wipers are in the down position (away from the windshield).
Directly above the generator door are several Phillips head screws holding the top of the front clip brackets to a square tubing frame just below the windshield. Remove these screws. Mine had four screws, but it appears there could be more, depending on who put them in. They are self tapping screws.
At this point decide whether you are going to remove the front clip, tilt it all the way down, or just partially tilt it. If I have to do this operation again, I will try to just partially tilt it, using the main connection bolts to support it. If you need to tilt it all the way, you need to disconnect the windshield washer fluid bottle and plug the bottom of it at this time. You will also need to disconnect the wire to the washer pump. If you are going to partially tilt it, make sure there is enough slack in the wire and tubing to allow it to move about a foot.
It’s now time to loosen the 4 bolts holding the front clip to the frame using a ¾” wrench and ratchet. Don’t loosen them much, as you don’t want too much play in them when you tilt the front clip down. It’s best at this point if you have someone to watch the lower corners on each side to make sure they don’t get against the sides when you tilt it down. Gently tug on the front from the top of the generator door opening until the front starts tilting forward. Once you begin tilting it, be aware the slots in the main frame connection could allow the front clip to drop several inches. The top slot goes front to back, and the bottom slot goes top to bottom to allow adjustment of the front clip. Looking at the top slot leads me to believe the front clip will tilt far enough to remove the heater core. If not, remove the top bolts and lower the front clip forward and rest it on a step ladder or something a couple of feet tall. I placed my trim stool below the generator door, as I felt it was the strongest area.
Disconnect the heater hoses from the heater core. I’m not sure it makes any difference, but the directions indicate flow direction in the core, so make sure you know which line comes from the motor, and which goes back. The intake to the heater core is the back nipple. Either plug the lines, or using a heater hose splice, connect the two together until you’re ready to place them on the new core.
It’s now time to remove the clips around the heater core box. There are sixteen clips, four on each side. Although the directions say it is necessary to disconnect the A/C lines, it is not necessary. The box will now just pry apart. The box is kind of brittle, so be gentle taking it apart. Once apart, the heater core will come right out with a little bit of coaxing.
Putting the new core in is another story. I had quite a time trying to get the new core in the box. The core now comes with the nipples on it, and they say it is not necessary to remove them before putting it in. It is definitely a tight fit. I used an old framing hammer and a wooden shim to spread the box. Placing the head of the hammer against the left side of the box, I used the shim to make the hammer just long enough to spread the box so I could get the new core in. Cutting a wooden stick a little longer than the width of the box would do the same thing.
Now it’s time to go back together with everything. It’s not bad, just the opposite of how you took it apart. The clips can be kind of a pain to get back on, but be patient, and you can do it! You’re just about to get over the hump! Going back together, make sure you get all the perimeter screws in before tightening the main frame bolts. It will be necessary to get them a little snug so things don’t move too much while going back together, but getting them too tight initially could create problems getting the perimeter screws back in. Also, don’t forget the wiper linkage goes on easiest if the wipers are in the down position. Wish I could give you some tricks to the caulking and double stick tape on the trim pieces, but can’t. Just be diligent and make sure they are completely clean before putting them back together. Don’t know what type of caulking to use, but I used the same that I use on the roof joints.
By not removing the front end completely, my guess is I save at least an hour. I might be wrong on that, because I didn’t work on it straight through. The race was on, and I had to watch it! I had the front end tilted and the heater core ready to come out in two hours, including getting the tools together, figuring out how it all came apart, and two trips to the parts store to get the right torx driver. All in all, if I have to do it again, I think I’ll have it apart in an hour or less.
Good luck with your experience if you find you need to do this. I think anybody with just basic tools (other than the T40 torx driver) and a mechanical aptitude can do this easily in a day. It wasn’t nearly as tough a job as I had envisioned, and wish I had tackled it sooner.
I had no screws along the top
Before reconnecting the wiper blades turn the key on to re seat the wiper potions mine was of 90 degrees causing the to run opposite. Also be extremely careful you have the wiper were needed i bent one because i put them on just turned them on. Leave them off and watch how it moves before inserting them
I resealed the stripping with M1.