Highland Ridge Open Range – AC Capacitor & Fan Motor Service

The whine hit my ears before I even opened the roof hatch—a high-pitched grinding that shifted into a rattling buzz the moment the compressor tried to engage. After spending over 80,000 miles across North America in three different rigs, I’ve heard that sound too many times to ignore: the capacitor was shot, the fan motor was struggling against a dead load, and if I didn’t address it quickly, the compressor would be toast before the season ended. This is the reality of systems thinking in an RV. One part fails, but it almost never fails alone. From my hands-on experience with Highland Ridge Open Range units, I’ve learned to treat the rooftop AC as a chain reaction waiting to happen. A failed run capacitor doesn’t just stop cooling—it stresses the fan motor into overheating, leading to burned windings, which then forces the compressor to work in a vacuum, ultimately burning that out too. Most folks replace the capacitor, hand the keys over, and three weeks later, they’re receiving a call from a frustrated buyer whose whole AC system has gone dark. This guide covers both the capacitor and the motor together because fixing one without addressing the other is just a temporary patch on a ticking clock.

Replacing the Run Capacitor on Your Dometic/Coleman-Mach Unit

This single component sits between your fan motor and total AC failure. If you replace it early, you keep the whole system breathing. Wait too long, and you’ll be swapping out motors and compressors instead of just a $25 part.

Parts and Tools

• Replacement dual run capacitor matched to the microfarad and voltage rating on the old one (typically 5+5 µF at 370V for Dometic/Coleman-Mach units) — check current price
• Needle-nose pliers or tweezers for disconnecting small spade terminals from capacitor leads
• Multimeter set to capacitance mode (or ohms mode if capacitance unavailable) to test the old capacitor
• Insulated screwdriver (Phillips and flathead) for opening the AC shroud and accessing internal components
• Replacement fan motor assembly if the existing motor shows burned windings, seized bearing, or fails to spin freely after capacitor replacement
• Electrical tape or heat-shrink tubing to insulate and secure reconnected spade terminals
• Soft brush or compressed air to clear dust and debris from the AC shroud interior before reassembly

Step-by-Step Instructions

Step 1: Kill power to the rooftop AC unit

Locate the 120V breaker for your AC system in the main panel and switch it to OFF. Wait 30 seconds to allow any residual charge to bleed from the capacitor. This prevents shock and protects the compressor from sudden restart. Do not skip this step—a live capacitor can deliver a painful jolt even when the breaker is off.

Step 2: Access the AC shroud and photograph the layout

Climb onto the roof safely using a ladder and roof brackets. Locate the two or four fasteners holding the AC shroud in place—usually Phillips-head screws on the sides or corners. Before removing anything, take a clear photo of the capacitor terminals and their wire connections. This reference photo prevents reconnection errors and saves troubleshooting time later.

Step 3: Test the capacitor with a multimeter

Set your multimeter to capacitance mode. Touch the probes to the capacitor terminals and record the reading. A healthy dual run capacitor should show values close to the rating stamped on the case (e.g., 5+5 µF). If the reading is zero, extremely low, or the meter shows OL (open line), the capacitor is dead. If you lack a capacitance setting, switch to ohms mode; a dead capacitor reads infinite resistance.

Step 4: Disconnect the old capacitor and inspect the fan motor

Using needle-nose pliers, carefully pull the spade terminals off the capacitor leads. Set the capacitor aside. Spin the fan motor shaft by hand—it should rotate freely with minimal resistance. If the shaft is seized, the motor is burned out, or you smell burned insulation, the motor must be replaced along with the capacitor. A struggling motor will kill a new capacitor within weeks.

Step 5: Install the replacement capacitor

Position the new capacitor in the same location as the old one, ensuring it does not touch metal shroud edges or other components. Reconnect the spade terminals to the correct leads—match the terminal positions to your reference photo. If terminals are unmarked, the dual run capacitor is non-polarized, so either orientation works. Secure loose terminals with electrical tape or heat-shrink tubing.

Step 6: Replace the fan motor if needed

If the motor failed the spin test, unbolt it from the AC housing (usually two or three fasteners). Disconnect the motor leads and remove the old unit. Install the replacement motor, reconnect the leads to match the original positions, and torque fasteners snugly—do not over-tighten, as the housing is plastic. Verify the motor shaft spins freely before closing the shroud.

Step 7: Reassemble and test the system

Clean dust from the shroud interior with a soft brush or compressed air. Reinstall the shroud and tighten all fasteners evenly. Return to the breaker panel and switch the AC breaker back ON. Listen for a clean fan spin-up and compressor engagement within 10 seconds. The system should cool without whining, grinding, or rattling. If noise persists, kill power again and recheck terminal connections.

What works

• The AC restarts with a clean spin—full fan speed returns, and the compressor engages smoothly without that labored grinding noise that signals a capacitor in its final hours.
• Temperature stability returns; the thermostat stops cycling frantically every few minutes, a telltale sign of a bad capacitor forcing the system into chaos.
• You can handle this swap solo in under twenty minutes once the main breaker is off; no special training or service truck needed.

What doesn’t

• Sourcing can drag; I’ve seen fast-shipping claims evaporate into week-long waits when you’re living in the box and the mercury is climbing toward triple digits.
• If the motor or compressor have already been cooked by prolonged capacitor failure, this part alone won’t bring the system back—you’ll only discover that damage after you’ve done the swap.

I once swapped a capacitor on an Open Range, and the system still wouldn’t cool past 82 degrees—turned out the motor bearings were already shot, and the whole fan assembly needed replacing. That taught me to always listen to the fan on startup: if it sounds like grinding gravel, the capacitor alone won’t save you. Grab the RV AC dual run capacitor (Dometic/Coleman-Mach) and have a backup plan ready if the AC still underperforms after the installation.

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