Coleman Mach Everest VS 18 AC and Furnace Thermostat Compatibility for a 2018 Lance 1985

Updated 08/19/2026 | Published 08/13/2026

Question:

I have a 2018 Lance 1985 trailer with the 13.5 Colman Mach AC. The existing wall mount thermostat is an Airexcel 9430-336 series that controls both the AC and Heater. It has what appears to be 6 wires. I want to replace the AC with a Mach-C Everest Variable Speed RV Air Conditioner System - 18K Btu. I understand it will require a new compatible thermostat, however your info video for that thermostatCM35MR states its only applicable for AC, not heat. This is in spite of the product pic clearly showing Heatinch on the faceplate. It also shows only 4 wires connecting to the thermostat, Does this mean I would need to maintain 2 separate thermostats? The old Airexcel for heat only, and the new CM35MR for AC? That seems like a very restrictive and inefficient requirement.

asked by: Travis

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Expert Reply:

Hi Travis!

You will not need to keep two separate thermostats. I completely understand the confusion because some of the information for the Coleman Mach Everest VS 18 thermostat makes it sound like it only handles the air conditioner, but the thermostat included with the Mach C Everest Variable Speed 18,000 Btu system, part # CM35MR, can control your RV furnace as well as the new air conditioner.

The difference in the number of wires is because the Everest uses a different control setup than your older Coleman Mach system. Your existing 9430 series thermostat uses individual wires for several functions, while the Everest thermostat communicates with its matching control box using fewer wires. The control box then handles the commands for the variable speed air conditioner and provides the connection used to call for heat from the furnace. So you do not need six wires at the new thermostat just because your old thermostat has six.

That means when you replace the existing Coleman Mach with the # CM35MR, the new Everest thermostat becomes your main thermostat for both cooling and furnace heat. You will need to use the wiring and control components included with the Everest rather than trying to wire the new thermostat terminal for terminal like your existing 9430 series thermostat.

I’m glad you caught the conflicting information before getting into the installation, Travis. Having one thermostat controlling everything is certainly a cleaner setup than having one on the wall for the AC and another sitting next to it just for the furnace. Do you know which furnace you currently have in your Lance?

expert reply by: Heather A