Coleman RV AC Remote Sensor Wrong Resistance: Troubleshooting Guide

Quick Take

WARNING: Always disconnect power to the AC unit before testing or replacing sensors to prevent electrical shock.

You're dealing with a frustrating but common issue with RV thermostat sensors (often called AC sensors) on your 2013 Phaeton. The fact that your replacement sensor (correct part for your model - verify with dealer) is reading the same resistance as your "bad" sensor suggests either you received a defective replacement part, or there's actually nothing wrong with the sensors themselves. The dramatic difference between your working sensor and both "bad" sensors indicates you likely have a wiring issue, moisture infiltration, or the working sensor may actually be the anomaly. Since you've confirmed both thermostats work properly by swapping leads, the issue is definitely in the sensor circuit.

Common Causes

Temperature sensor resistance problems in RV AC systems commonly stem from moisture infiltration at connection points, which can cause erratic readings or complete sensor failure. In your Phaeton, the sensors are often mounted in areas prone to humidity and temperature fluctuations. Corroded connections at the sensor junction box or thermostat terminals can create false resistance readings.

Another possibility is that you received a defective replacement sensor, though getting two identical "bad" readings is suspicious. Sometimes old stock sits in warehouses for years, and NTC (negative temperature coefficient) sensors can drift over time. The replacement sensor may have different resistance characteristics than the original, despite being listed as a direct replacement.

Wire damage between the sensor and thermostat is also common, especially where wiring runs through cabinet areas or near slide-out mechanisms. Pinched or abraded wires can create intermittent connections that affect resistance readings. Given that one sensor reads differently, this suggests the thermostat circuitry may expect a specific resistance range for normal operation (verify specifications with manufacturer).

Preparation

Before proceeding, gather a digital multimeter capable of measuring resistance accurately, electrical contact cleaner, dielectric grease, and wire strippers. You'll also need access to your AC unit's wiring diagram, which should be in your owner's manual or available from Tiffin Motorhomes for your 2013 Phaeton.

Locate the sensor wiring path from each remote sensor back to its respective thermostat. In most Phaeton layouts, these wires run through the ceiling or wall cavities. Take photos of all connections before disconnecting anything, and have replacement wire connectors available in case you find corroded terminals.

Contact your parts supplier to verify the replacement sensor specifications match the original. Request the resistance curve data for both part numbers to confirm they're truly equivalent. Some suppliers can provide technical data sheets that show expected resistance values at various temperatures.

Repair Steps

WARNING: Ensure all power is disconnected before working on electrical connections.

Start by measuring the resistance of your "good" sensor while disconnected from both ends of the circuit at a known ambient temperature (ideally 68-77°F room temperature). Next, temporarily connect your new replacement sensor directly to the working thermostat using short jumper wires to bypass the existing wiring completely. Ensure testing is done at the same ambient temperature as your baseline measurements for accurate comparison.

If the new sensor works properly with direct connection, the problem is in your wiring harness. Inspect every connection point between the sensor and thermostat, cleaning contacts with electrical contact cleaner and applying dielectric grease. Look for green corrosion, loose connections, or damaged wire insulation.

Test continuity through each wire individually from sensor to thermostat. You should see near-zero resistance through each conductor. If you find high resistance in the wiring, you'll need to run new sensor wire. Use wire matching the original gauge (verify original wire specifications), two-conductor thermostat wire rated for the temperature range your RV experiences.

If direct connection of the new sensor still shows incorrect readings, contact your supplier immediately for a replacement. It's possible the entire batch of replacement sensors has incorrect specifications. You may need to source an original sensor from a different supplier or find an alternative part number that matches your working sensor's characteristics. Note that NTC sensor resistance values are temperature-dependent - consult manufacturer specifications for expected resistance values at specific temperatures to properly evaluate sensor function.

When to Get Help

Call a professional RV technician if you discover the wiring runs through inaccessible areas requiring interior panel removal or if you're not comfortable working with electrical connections. Many RV service centers have experience with Phaeton AC systems and can quickly diagnose sensor circuit problems.

Contact Tiffin Motorhomes technical support directly if you can't resolve the part number discrepancy. They maintain detailed records of original equipment specifications and may be able to provide the correct replacement part number or technical guidance specific to your 2013 Phaeton's AC configuration.

If multiple sensor replacements continue to fail, there may be an underlying issue with the thermostat's sensor input circuit that's damaging sensors. This type of electronic troubleshooting requires specialized knowledge and test equipment that most DIY RV owners don't have access to.