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Recommended Mach 8 Plus AC w/ Heat Pump and Components to Replace a Coleman Mach 10  

Published 09/07/2026



Question:

Good morning .... I curently have 3 Mach 10 15K units on my GD 390RK, AC only. They are connected to Coleman Thermostats 9420-381. I would like to replace them with Mach 8 Plus units with Heat strips in 2 of them. Do I need new interior trim panels with the Mach 8 units?

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Expert Reply:

You sure do Thomas and good morning to you as well. The Mach 8 Plus units do indeed require a air distribution box or trim on the interior of your Grand Design. To replace your three Coleman Mach 10 15K AC units, you will need the following parts and the quantity listed next to them:

Qty 3 item # CM74MR in black or item # CM95MR in white - Mach 8 Plus RV AC w/ Heat Pump

Qty 3 item # CM48GR - Coleman-Mach CHILLGrille Ducted Ceiling Assembly or item # CM98GR if your Grand Design has a ductless setup.

Qty 3 item # CM84MR - Coleman-Mach Heat Ready Heat Pump Control Kit

Qty 2 item # CM24MR - Coleman-Mach 120 V Heat Strip Kit

Qty 3 item # CM46MR - Coleman-Mach WiFi Thermostat for RV Air Conditioners and Heat Pumps or item # CM76RR for a standard thermostat.

Please note that, your Coleman Thermostats pn 9420-381 are not compatible with the new R32 Mach 8 Plus AC systems. This is the same for the air distribution boxes. Without knowing what model year your Grand Design is I wasn't able to tell if you have air ducts, which is why I recommended options for both. Each of the AC units will also need a control box. You will be able to reuse all of your existing wiring for powering the system and the thermostat wires controlling them.

What rooms or areas in your Grand Design are going to have the new heat strips in them? Feel free to answer this and throw in any other questions you have, where it says Add Comment.

expert reply by:
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Jerred H
Wireless Coleman Thermostat
Wireless Coleman Thermostat
(click to enlarge)
Coleman Thermostat
Coleman Thermostat
(click to enlarge)
Mach 8 Plus
Mach 8 Plus
(click to enlarge)
Thomas T. profile picture

Thomas T.

9/7/2026

Jerred ... Thank you .... it is a 2024 GD 390RK .... Planned Mach 8 Plus units with heat strips in Kitchen and Bedroom .... Mach 8 Plus without heat strip in Living room (using current propane furnace) ... Current wiring is Red, Blue, Yellow, Green, Brown in the Bedroom and Kitchen .... Red, Blue, Yellow, Green, Brown, White, Orange in the Livingroom. +12V DC Power Red 12V Ground (Negative) Blue Cooling Compressor Yellow High Fan Speed Green Low Fan SpeedGray BR Furnace / Heat White (Current Livingroom only) I know that the Orange is for the reversing valve when there is a heat pump. The wire bundle in the kitchen has the White and Orange wires cut back and not connected. Does the new thermostat utilize the same wires plus I will need to connect the White and Orange wires in the Kitchen and Bedroom? It looks like the pictures of the CM76RR use one white wire and one white wire with a black tracer .... I assume the white with black tracer would connect to the orange wire for the reversing valve.

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