Replace Mach 8 Rooftop Unit

[Mwoodofd]

Looking to see if anyone has experience replaced one of the Mach 8 Heat Pump/AC units yourself. My rear unit is out, and I plan to order one next week on line and ship it to my business facility. I have fork lifts, so getting the unit up and down from the top of the motor home is no problem.

I completely removed the AC unit earlier today just to see what would be involved. Removed 4 screws for the outer cover, 4 for the inner cover, and 4 holding the unit to the roof. Took 10 minutes. Took images with the cell phone of all connections, pieces, parts and moved it back. Seems to be an easy exchange.

I am not clear on what comes with the unit when ordered. Mine is the Heat pump and AC version, 15K BTU and 6000 BTU Heat pump. I plan to order the same unit, with the condense pump. When I order, I will ask if the new unit comes with the image below that contains the board, and the connections for the wires. If anyone has any experience with exchanging one of these, and words of wisdom, I plan to replace it next weekend.



It seems too easy - and the hard part is getting the units on and off the roof, which I can?? I will also ask if the seal comes attached to the unit on the bottom around the openings - appeared to be factory attached?

[Rollin101]

Originally Posted by Mwoodofd

Looking to see if anyone has experience replaced one of the Mach 8 Heat Pump/AC units yourself. My rear unit is out, and I plan to order one next week on line and ship it to my business facility. I have fork lifts, so getting the unit up and down from the top of the motor home is no problem.

I completely removed the AC unit earlier today just to see what would be involved. Removed 4 screws for the outer cover, 4 for the inner cover, and 4 holding the unit to the roof. Took 10 minutes. Took images with the cell phone of all connections, pieces, parts and moved it back. Seems to be an easy exchange.

I am not clear on what comes with the unit when ordered. Mine is the Heat pump and AC version, 15K BTU and 6000 BTU Heat pump. I plan to order the same unit, with the condense pump. When I order, I will ask if the new unit comes with the image below that contains the board, and the connections for the wires. If anyone has any experience with exchanging one of these, and words of wisdom, I plan to replace it next weekend.

Attachment 251568

It seems too easy - and the hard part is getting the units on and off the roof, which I can?? I will also ask if the seal comes attached to the unit on the bottom around the openings - appeared to be factory attached?

Attachment 251569

Mark, these are the measurements Airxcel gave Ray when he was replacing his blower wheel. They think the factory doesn’t abide by these measurements when installing the units.
Just thought you might like to have them for your install.

. They (Airxcel) like to see the front and rear of the AC base pan 1” from the roof with less than 1/4” deviation from the rear measurement to the front measurement. Unfortunately once you compress these gaskets you can not safely re-torque the hold down bolts without risking a leak.

Also I thought Entegra put a bead of sealant around the base of the gasket before setting the unit, but I’m not positive about that.

[Bikinjim]

I had a Mach 8 go out on my 2017 Tiffin RED and got it replaced on a trip while in Gulf Shores, AL while under warranty. Because the shop was really busy, I helped the installer to get it done before a thunderstorm hit. My new unit included the gasket seal but did not include the connection board (just used the board from the original unit). And Tiffin did lay down a bead of silicon on the roof before setting the original gasket and unit down. As I recall, the toughest part was cutting through the gasket so the unit could be lifted and then cleaning up the silicon/gasket remains so a watertight seal could be created with the new unit. Then, a new bead of silicon was laid down and the new unit was set and bolted down (the installer commented that the gasket supplied provides a watertight seal by itself and the silicone use is not desirable, however, he said once silicon is used on a roof it should always be used from then on to prevent leaks). Because Tiffin uses a ducted installation, the installer cut a piece of foam to make a new baffle and installed that in the new unit (he made a new baffle because the original could not be removed intact due the glue used during original installation which resulted in chunks missing when it was removed), plugged in the connection board, hooked up the condensate pump, and installed the cover. BTW, the new unit delivered was the then newly redesigned Mach 8 Plus which turned out to be a bit quieter than my original Mach 8.

[Mwoodofd]

Thank you, does not seem like there was a 1" gap between the pan and the roof - maybe about half an inch. There was also no silicone between the roof and the seal on the unit - once the bolts were out, it lifted right up. The roof image below of the openings is how it looked, just the dirt under the unit, which I will clean up. I've read all the installation instructions and they are not real specific about anything. I have had no leaks either.

I also noticed that Airxcel if fairly competitive on line - not sure if freight is included - I will update my progress.

[Rollin101]

Originally Posted by Mwoodofd

Thank you, does not seem like there was a 1" gap between the pan and the roof - maybe about half an inch. There was also no silicone between the roof and the seal on the unit - once the bolts were out, it lifted right up. The roof image below of the openings is how it looked, just the dirt under the unit, which I will clean up. I've read all the installation instructions and they are not real specific about anything. I have had no leaks either.

I also noticed that Airxcel if fairly competitive on line - not sure if freight is included - I will update my progress.

I don’t think Entegra started sealing around the gaskets until 2-3 years ago.

[Jburklo]

We had our #3 replaced and was reminded to use two gaskets. Entegra installed two on our 2012 Aspire and made that recommendation. You might call them to confirm.

Good luck a nd look forward to reading your success!!!

[Mwoodofd]

Originally Posted by Jburklo

We had our #3 replaced and was reminded to use two gaskets. Entegra installed two on our 2012 Aspire and made that recommendation. You might call them to confirm.

Good luck and look forward to reading your success!!!

That would make the gap from the roof to the bottom of the AC pan closer to 1" that was suggested earlier. Thanks for the suggestion, and I will confirm with them, and on using sealant with the gasket(s).

We will be in Austin later in July to move daughter to another Apt, so we will need the unit!!

[mlwhitt]

I replaced mine a few months ago also. I would look at rv parts country and also adventure rv for best price. Internet sales only. As others have said it is a easy swap. It will arrive with no circuit board.

[voltdoc]

Just replaced our #3 couple weeks ago on our '17. Had it replaced by a mobile repair unit and covered by our extended service contract.

New unit did not come with the controller, old one had wingnuts so it is simple to remove and replace without disconnecting any of the wiring.

There was no silicone on the old, nor did the installer add any. IMO I would not silicone unless you experience a leak.

The gasket and supporting blocks came installed on my unit as shown in the photo. The gasket material is about 1" thick and not easily compressible providing a stable yet watertight mount.

However, there is one key piece of foam missing as shown. The missing piece separates the supply air from the return air. It needs to line up with the roof section separating the ductwork. I don't know yet if it is supposed to be installed by Coleman or in the field, I have a call into Coleman. In either case mine was not, so make sure it's there.

That had me running around in circles for a couple weeks. Unit put out nice cool air but would run for hours without being able to drop the temp by even 1 degree, then eventually freeze up. When I finally discovered the omission I fixed with a piece of gray foam pipe insulation compressed into the gap.

For an already installed unit one test is to put a paper napkin on the return grill, the negative pressure should hold it. If it doesn't then the return air flow has an issue and possibly the gasket is missing.

[Mwoodofd]

Thanks for the head up Rob - my luck will be no gasket between them. I will look on my current unit to see if it is there. (cant remember) My units will hold the return vents in place with the filter installed and the screws removed - hopefully the seal is on there.

ML - I will take a look on line - so Far Dyers has the best I have found with free shipping on the replacement unit.

[Gary.Jones]

Make sure that you get the model exactly right. I had all three Mach 8 AC units installed on my rig (due to hail damage) by a dealer and the ones they installed were AC only Mach 8 units. Once we discovered we had no heat pumps for fall and spring when we tried to use them, then the dealer had to order new units which had both AC and heat pumps in them at their cost. It was a real mess!!
.. -- .. Make sure that you buy what you think you are buying... the dealer's parts man missed the differences. Who knew???

Gary

[Mwoodofd]

Thanks Gary - I have been researching this for a few weeks and see the differences between all the units. Our's are the Mach 8 AC with Heat Pump and Condense Pump, 15,000 BTU and 6000 BTU Heat Pump.

I did go on the Airxel Web Site and put in my old model number, right off the label and it crossed it to the new number 47024-879B - which I will confirm when I talk to them. - Looks like a easy change since I have access to Fork Lifts.

(looking at Robs image - that looks like a cool lift, but the power lines overhead are a concern)


There is an Electrical Heat Element that can be installed in these, or some of their units, but our rigs don't appear to use that.

[BonS]

On my coach, the four bolts to tie down the unit we're too short for the new unit. I had to get, and cut, some allthread to adapt and improvise. It worked out perfectly in the end. The new unit came with a new gasket, and I didn't use any additional sealant. No leaks.

[Mwoodofd]

Originally Posted by BonS

On my coach, the four bolts to tie down the unit we're too short for the new unit. I had to get, and cut, some allthread to adapt and improvise. It worked out perfectly in the end. The new unit came with a new gasket, and I didn't use any additional sealant. No leaks.

The screws in mine had about 1.5" of thread to tighten, and one of them was about 1.5" longer than the other 3. Wonder whats up with that?