Coleman-Mach Wall Thermostats: Single-Zone, Digital, Multi-Zone, and CAN-Bus

Overview - four families, one color code

Coleman-Mach coaches use four distinct wall-control families, and identifying which one you are facing is the first service step. All of them run on 12 VDC control power, not 24 VAC - a residential thermostat is never a drop-in substitute. Three of the four share the Coleman low-voltage color code: red R (+12 V), blue B (-12 V/ground), yellow Y (compressor), green GH (high fan), gray GL (low fan), white W (gas heat/furnace).

Single-zone button thermostat (9430 series)

A small vertical LCD stat with up/down arrows and a mode button. Cool-only versions are 9430*339, *340 and *342; heat/cool versions are 9430*335 through *338 (the asterisk position varies by finish). Setpoint range is 33-99 F in both modes. It carries a replaceable 2 A blade fuse on its base - a mis-wire or shorted control circuit opens the fuse, and the cause must be found before fitting a new one. The control circuit must not exceed 1 A; OEM wiring is minimum 18 gauge. A three-minute anti-short-cycle timer protects the compressor after every cooling cycle; switching the mode to OFF bypasses it during service. Holding the mode button five seconds toggles Fahrenheit/Celsius. Models *335 and *342 accept a remote room sensor, which then fully replaces the internal sensor. Functional test after install: LO FAN energizes GL, HI FAN energizes GH, a cooling call adds Y to the selected fan wire, and a heat call energizes W only.

Digital knob thermostat (9420*381 / 9420*382)

The newer single-zone control: black screen, white LCD, one rotary push-knob. Wiring lands on push-in connectors for 20 AWG solid wire (strip 5/16 inch, gauge printed on the housing); the *382 variant ships with plug harnesses instead. Terminals: R, B, Y, GH, GL, W (gas heat) and WHP (electric heat - heat pump or strip-heat accessory), plus SENS for a remote sensor (8330-5191 white, 8330-3101 black). Protection is a self-resetting PTC fuse. Two dip switches on the back must match the coach equipment - switch 2 selects Gas only (default) versus Elec+Gas heating, switch 3 selects Cool+Heat auto-changeover (default) versus Cool Only - and any change requires a reboot (hold the knob 12 seconds). In electric-heat mode the stat runs a strike system: if room temperature falls 5 F below setpoint, gas heat assists and the electric heat takes a strike; three strikes disables electric heat for 1 hour 45 minutes with gas as primary (the Elec segment flashes while gas runs). A 3-minute short-cycle delay guards the compressor and heat pump, and in cool+heat mode a 15-minute changeover timer prevents mode ping-pong when room and set temperatures sit within 2 F.

Legacy multi-zone system (9330-33* thermostat + zone control boxes)

One wall stat controls up to four zones; each zone has a 12 VDC control box in the air conditioner's return-air plenum. Two jumpers on every zone board must be set with all power removed: the zone number jumper (zone 1 at the front of the coach, progressing rearward) and the HP/NON-HP jumper telling the board whether its unit is a heat pump. The stat connects over a twisted signal pair (purple/black, about 4 turns per inch) plus power and up to four 12 V heat-appliance outputs. Zone 1 may use the stat's internal sensor; zones 2-4 always need remote room sensors wired to the ROOM terminals of their control boxes. To program appliance types: set SYSTEM to OFF, hold both arrow buttons about five seconds until the LCD flashes, select each zone with ZONE, choose the installed appliance combination with MODE, then press SYSTEM to exit - stored permanently, and it only needs doing once. Defaults are 78 F cool / 68 F heat. There is a deliberate delay of roughly ten seconds between a setting change and the units responding (the stat waits idle, sends, and verifies the command). The green LED visible through the control-box opening flashes the zone number at power-up and goes solid when communication is up; the system does not operate below 9.75 VDC. Heat-pump lockout logic: if electric heat cannot hold within 5 F of setpoint, gas assists (GAS flashes); three consecutive assists lock electric heat out for two hours.

CAN-bus multi-zone touchscreen (9420-330)

The current multi-zone control: a 4.3-inch touchscreen stat networked to NetZone control kits over CAN (RV-C style). Compatible kits are 9430-754 (cool only), 9430-758 (cool/heat) and 9630-758 (heat pump). The four-wire harness (RVP 9530-395) carries red +12 VDC, blue -12 VDC/ground, green CAN L and yellow CAN H; a 120-ohm terminating resistor is built into the stat and a Zone 1 resistor ships in the box. Operating voltage is 9-16 VDC, standby draw 13 mA. Zones 2-4 require the 8330-310 zone temperature sensor at the control box; zone 1 may use either a remote sensor or the stat's internal thermistor (enable Use Internal Thermistor on the Zone Setup page - the display shows dashes until the zone controller reports a temperature). Zone count and per-zone Gas/Elec heat sources are enabled on the Settings > Zones page. The stat will not mix modes: with any zone in Heat, Cool is hidden everywhere (and vice versa), and all zones must be set to Off before changing between Heat and Cool. Gas assists electric heat when electric runs more than 20 minutes without reaching setpoint or the room drifts more than 4 F (2 C) from setpoint. It can also drive RV-C MaxxFan ventilation products when enabled. A diagnostic status LED on the back of the stat reports network health.

Which stat is on this coach?

Buttons with a small segment LCD: 9430 single-zone. Rotary push-knob: 9420*381/382. Segment LCD with ZONE/MODE/SYSTEM buttons and zone digits 1-4: legacy 9330-33* zone system. Color 4.3-inch touchscreen with ZONE tabs: 9420-330 CAN-bus. The distinction matters most on multi-zone coaches, because the legacy system diagnoses over the twisted signal pair and jumpers, while the CAN system diagnoses with the status LED and network wiring.