Coleman Mach RV AC Not Cooling

As an RV owner, few things are more frustrating than an air conditioner that isn’t cooling properly on a hot summer day. If you own a Coleman Mach RV, you may have experienced the common issue of inadequate or no cooling from your AC unit. Don’t sweat it – this guide will walk you through the systematic troubleshooting steps needed to diagnose your Coleman Mach RV AC problems and get your cooling back online.

Having personally dealt with a non-functioning AC in my RV, I know how disruptive it can be to vacation plans and overall RV enjoyment. My goal is to empower you to address these cooling issues yourself whenever possible, saving you time, money, and frustration. Whether it’s a quick fix or a more involved repair, you’ll have the knowledge to tackle it head-on.

We’ll explore potential issues ranging from low refrigerant levels to thermostat malfunctions to improper maintenance. I’ll provide actionable tips for inspecting key components like your compressor, capacitors, and control boards. You’ll learn how to spot warning signs of larger problems, and when it’s best to rely on a professional.

With the helpful troubleshooting advice in this guide, you’ll be able to confidently diagnose and resolve the most common Coleman Mach RV AC problems. Let’s get started!

Coleman Mach RV AC Not Cooling

Troubleshooting Overview

When your Coleman Mach AC fails to blow cold air, there are several areas to inspect –

Source: mortonsonthemove

Refrigerant level: Low levels can drastically reduce cooling capability. Checking for leaks and adding refrigerant may resolve cooling issues.

Thermostat and capacitors: Faulty components can prevent the AC from turning on or operating efficiently. Testing with a voltmeter can identify problems.

Fans and compressor: Dirty or obstructed fans and compressor issues affect performance. Thorough cleaning and inspection are key.

Coils and fins: Clogged or damaged coils and fins lead to inefficiency and overheating. Careful cleaning can restore proper operation.

Power supply and control panel: Power or electrical control problems will shut the AC down. Checking connections and control boards can identify causes.

Recharging and leaks: Significant refrigerant loss requires recharging by a professional. Technicians can also detect leaks needing repair.

Thoroughly inspecting these areas and components is crucial to pinpoint the issue. Let’s explore each area more in-depth.

Low Refrigerant Level

One of the most common reasons a Coleman Mach RV AC unit fails to cool properly is low refrigerant level. RV air conditioners operate as a sealed, self-contained system. The refrigerant is the medium that absorbs heat from the air as it passes over the coils.

With inadequate refrigerant, the AC system cannot effectively absorb and reject heat as designed. Symptoms of low refrigerant include –

  1. Weak cooling capability
  2. Longer cooling cycles
  3. AC freezing up due to reduced efficiency
  4. Higher electric bills from AC struggling to cool
  5. Compressor damage from overwork

Significant refrigerant loss is usually caused by a leak in the sealed system. Tiny leaks may slowly reduce the level over time. Larger leaks can lead to a rapid loss of refrigerant. Diagnosing and addressing the cause of the leak is crucial – simply recharging without repair will lead to repeated loss.

Checking Refrigerant Level

Verifying if refrigerant level is the culprit is an important first step. Here is how to check –

Step 1: With the AC turned on, carefully feel the suction line – the larger refrigerant line entering the RV. It should feel noticeably colder than the discharge line.

Step 2: Place an infrared thermometer on both lines at the compressor. The suction line should read a minimum of 15-20°F lower than the discharge line. Significant variance indicates an issue.

Step 3: Listen to the operating compressor. Noticeable gurgling or bubbling noises point to low refrigerant.

Step 4: Check sight glasses on the AC unit if equipped. Bubbles or foam indicate lower than optimal refrigerant.

Step 5: Use an HVAC gauge kit to directly test pressure on the suction and discharge lines. Specs vary by Coleman Mach model – compared to unit recommendations.

Step 6: Have an RV technician perform thorough refrigerant testing to verify the level and pressure.

If your AC unit is over 5 years old, gradual refrigerant loss is likely even without an obvious leak. Responsibly recharging the system may be needed to restore cooling capability if other issues are ruled out.

Checking for Leaks

Pinpointing how refrigerant is escaping the sealed system is key to preventing repeated loss after recharging. Here are tips for checking for leaks –

Step 1: Visually inspect all refrigerant lines and joints for obvious cracks, damage, or corrosion. Oily spots indicate potential leakage points.

Step 2: Listen and feel along the lines of any subtle hissing noises or vibrations. Refrigerant escaping a leak point can be detected.

Step 3: Use leak detection dye injected into the system. When viewed under UV light, dye staining will pinpoint leak points. A professional should perform this.

Step 4: Electronic leak detectors can sense refrigerant gases in the air surrounding lines and fittings. Very small leaks can often be found.

Step 5: Pressure testing involves isolating sections of the system and monitoring pressure decay. Sudden loss indicates a leak. Best performed by a technician.

Note that spray-on bubble solutions are not effective for RV ACs. The most thorough approach may involve a combination of the methods above. Identifying all leaks for repair is critical before recharging.

Refrigerant Recharge and Repair

With very low refrigerant, your Coleman Mach AC will likely require recharging by a qualified RV technician once all leaks have been repaired. Due to EPA regulations, refrigerant cannot be purchased by individual RV owners – specialized equipment and certification are required.

Recharging is complex and must be done precisely based on your AC unit’s factory specifications. Overcharging can damage the sealed system over time. Precision recharging using a digital charging scale optimizes cooling performance and system longevity.

For major leaks or after a second recharge, full system replacement may be your most cost-effective option. An upgraded, leak-free AC can provide better, more efficient cooling for years before any servicing is needed.

Thermostat and Capacitor Issues

The thermostat and starting/run capacitors are critical electronic components that manage the major functions of your Coleman Mach RV AC.

The thermostat activates the AC based on desired temperature settings and room conditions. Electrical signals initiate cooling cycles.

The starting capacitor provides the jolt of power needed to initiate compressor operation. Gets it spinning from a standstill.

The run capacitor works to keep the compressor and fan motors running smoothly after startup. Prevents motor damage.

Issues with the thermostat or capacitors can prevent the AC from turning on, lead to irregular operation, or reduce system efficiency –

  1. A bad thermostat fails to properly initiate cooling cycles, even though power is present.
  2. Weak starting capacitors cause compressor or fan motor failure on startup.
  3. Bad run capacitors result in AC blowing warm air or cycling on and off irregularly.

Let’s explore troubleshooting these components.

Thermostat Testing

A voltmeter allows you to directly check your Coleman Mach AC thermostat –

Step 1: Set the thermostat well below room temperature to call for cooling.

Step 2: Locate the thermostat wiring panel – remove the cover if needed.

Step 3: Using a voltmeter, check for 24V power between thermostat wire connections when cooling is called for.

Step 4: If voltage is present, the thermostat is calling for cooling. If not, it is likely defective.

Step 5: Compare your voltage readings to unit specifications as some models may vary.

If the thermostat tests functional but the AC still fails to engage, the issue lies elsewhere. But a bad thermostat identified here would be the cause. Basic RV thermostats are often inexpensive and easy to replace yourself.

Capacitor Testing

Capacitors can go bad over time without any visible sign of failure. Testing capacitance is the best way to identify issues –

Step 1: De-energize the AC – disconnect the shore or battery power source.

Step 2: Remove the protective cover from the capacitor(s) you are testing.

Step 3: Discharge the capacitor by shorting the terminals with an insulated screwdriver.

Step 4: Use a multimeter, setting it to test capacitance in microfarads (uF).

Step 5: Touch the meter prod tips to the capacitor terminals. Make note of the capacitance reading.

Step 6: Repeat the test across all terminal combinations and compare to manufacturer uF specs.

Significantly lower than specified capacitance indicates replacement is needed. Attempt to restart the AC to confirm the issue is resolved. Be extremely careful when testing capacitors – discharge fully before handling.

DIY Capacitor Replacements

On many Coleman Mach models, starting and run capacitors can be easily replaced DIY –

Step 1: Order an exact replacement based on the uF rating and voltage specifications printed on the capacitor.

Step 2: With AC power disconnected, discharge the old capacitor before removing all wires.

Step 3: Mount and secure the new capacitor in place of the old one and reconnect all wiring.

Step 4: Power up the AC and monitor operation. The problem should be resolved if the diagnosis is correct.

Larger AC units may have multiple run capacitors requiring identical replacement sets. Take photos of the wiring before disconnecting. Always exercise caution when working with electrical components. Capacitors hold high voltage charges.

Fan and Compressor Inspection

For an RV AC system to function efficiently, both the interior fan and exterior compressor need to operate properly in tandem. Any obstruction, restriction, or component wear will reduce cooling performance. Let’s explore proper inspection and maintenance:

Fan Blade and Motor Check

A dirty or obstructed AC fan cannot properly circulate air across interior coils. Regular cleaning is essential –

Step 1: Remove the fan cage cover to expose the blades. Visually inspect blades for debris buildup.

Step 2: Use a soft brush attachment on a vacuum cleaner to dislodge dust and dirt from fan blades.

Step 3: Wipe down with a dry microfiber cloth or compressed air. Avoid moisture or harsh chemicals.

Step 4: Ensure blades are not bent – carefully straighten or replace warped blades.

Step 5: Check that the fan spins freely by hand with the power disconnected. Listen for grinding.

Step 6: Power on and listen for abnormal noise. Replace the fan motor if excessive noise is heard.

Your Coleman Mach AC likely relies on variable fan speed to optimize efficiency. Any restriction on the fan reduces performance. Keep it clean for maximum airflow.

Compressor Maintenance

As the heart of the AC system, compressor maintenance is also vital –

Step 1: Start by visually inspecting the exterior compressor for damage, rust, or leaks. Repair any housing damage detected.

Step 1: Carefully clear away debris or vegetation touching the compressor. Ensure adequate airflow around the unit.

Step 2: Check that the base is level – shim or adjust to prevent vibration and noise.

Step 3: Inspect refrigerant lines, joints, and valves. Tighten fittings or replace damaged components as needed.

Step 4: Test that the compressor amp draw is in spec under load. High amps can signal issues.

Step 5: Listen for odd noises or grinding sounds. Have the compressor replaced if severe issues are heard.

With proper inspection and maintenance, the fan and compressor can continue providing reliable, efficient cooling.

System Overheating and Frost Build-Up

Inadequate cooling can result from the AC system overheating during operation. Additionally, frost build-up on interior coils reduces system efficiency over time. Let’s examine how to troubleshoot these issues:

Identifying Overheating Problems

Look for these signs of AC system overheating –

Step 1: AC cycles on and off rapidly run for short bursts

Step 2: The unit does not blow cold when the exterior temp is hot

Step 3: Noticeable burning smell from the AC

Step 4: Higher-than-normal energy use for limited cooling

Step 5: Exterior AC components or refrigerant lines feel hot to the touch

Overheating often results from restricted airflow through a clogged AC coil or fins. Proper cleaning is essential to prevent premature compressor failure.

Cleaning Coils and Fins

Here is a step-by-step guide to cleaning AC coils and fins –

Step 1: Disconnect power to the AC before servicing. Remove any protective covers.

Step 2: Wear protective eyewear and gloves – fins are delicate and sharp.

Step 3: Use a fin comb tool or blunt plastic utensil to straighten any bent fins.

Step 4: Clean fins of debris and dust using compressed air and a soft brush.

Step 5: Flush fins with a garden hose on a low-pressure, fan-spray setting.

Step 6: Rinse coils from the top down. Avoid excess water pressure.

Step 7: Straighten flattened fins with a fin comb. Be gentle – fins damage easily.

Step 8: Replace filters if equipped. Upgrade to pleated filters for better particle capture.

Proper AC fin and coil maintenance at least annually can prevent serious overheating issues and extend the system’s lifespan.

Addressing Ice and Frost Build-Up

If AC output airflow becomes obstructed, moisture can freeze on the interior coils. Signs of frost build-up include –

  1. Reduced cooling and airflow from vents
  2. AC freezing up, icing over
  3. Interior coils developing frost or ice
  4. Frozen condensate drain line

For minor frost, allow the AC to defrost and air dry fully before restarting. For heavy ice accumulation –

  1. Turn the AC off and allow the ice to thaw. Capture dripping water.
  2. Inspect coils once thawed – clean any debris/dirt buildup. Straighten fins.
  3. Check AC filters – replace and upgrade if dirty.
  4. Make sure thermostat and refrigerant levels are optimal.
  5. Monitor AC carefully on the restart to ensure frost does not reoccur.

Persistent heavy frost build-up can indicate a refrigerant issue or compressor problem. Have your Coleman Mach AC serviced by a technician in these cases to prevent compressor damage.

Power Supply and Control Panel Problems

Electrical power issues are another cause of AC failure. Additionally, problems with the control panel can shut down cooling or cause intermittent operation. Let’s explore tips for troubleshooting these areas.

Checking Power Supply

Start diagnosis by ensuring power is available to the AC unit –

Step 1: Verify shoreline power connection is live and the circuit breaker is on. Check for a tripped breaker.

Step 1: For roof ACs, test circuit box connections and breakers supplying power.

Step 2: Turn the battery disconnect switch fully on if running AC on coach batteries.

Step 3: Inspect extension cords and adapters – ensure adequate gauge for AC power draw.

Step 4: Test the coach battery voltage. Charge or replace if below 12V.

Step 5: Try an inverter reset if using an AC power inversion system.

Loss of shore power tripped breakers, and dead batteries are common causes of RV AC failure. Verify adequate power to the unit before further troubleshooting.

Control Panel Inspection

If the power supply is verified, inspecting the AC control panel may reveal issues –

Step 1: Check for visible signs of corrosion, burnt spots, or damaged wires.

Step 2: Remove the cover and ensure the internal circuit board is clean and intact.

Step 3: Check all wire harness connections are snug and corrosion-free.

Step 4: Look for signs of moisture incursion or rodent damage.

Step 5: Test the operation of panel buttons and switches for responsiveness.

Step 6: Monitor diagnostic LEDs if present – refer to decoding in the manual.

Step 7: Assess if the panel fuse or circuit breaker needs replacement.

Control panels contain sensitive electronics and wiring harnesses that can malfunction over time, especially with moisture exposure or damage. Seek professional service for complex control board issues requiring electronics expertise.

Recharging and Leak Detection

As outlined initially, the significant refrigerant loss will make your Coleman Mach AC increasingly ineffective at cooling. While self-recharging is not advisable, professional recharging and leak detection can restore normal operation.

Refrigerant Recharge

If you have verified low refrigerant levels through pressure gauges and testing, recharging can help. But keep these factors in mind –

Due to EPA rules, RV owners cannot purchase refrigerant. A certified RV technician must perform recharging.

Simply adding refrigerant without addressing leaks will lead to repeat issues. Leak testing is essential first.

Reputable shops will evacuate the system and vacuum to remove moisture before recharging to factory specifications.

Avoid shops that simply “top off” refrigerant through the service valve – this leads to issues over time.

Precision digital recharging using calibrated scales is the preferred method.

Request the use of a high-quality PAG oil to aid system lubrication and efficiency.

Responsible refrigerant recharge by qualified professionals is the only way to ensure lasting results. DIY attempts often lead to costly issues.

Professional Leak Testing

As refrigerant does not simply vanish, fixing leaks before recharging is critical. Technicians have advanced diagnostic options –

Electronic leak detectors can pinpoint very small, slow leaks undetectable otherwise.

Fluorescent dye introduced into the system will illuminate leaks under blacklight inspection.

Sections of the system can be isolated and pressure tested to identify leakage points.

A halo light kit draws refrigerant into a clear tube – escaping bubbles reveal leaks.

Only by locating and repairing all system leaks first can a professional recharge offer lasting relief. Avoid any shop that recommends quick “top-offs” without proper leak testing.

Frequently Asked Questions

Why does my Coleman Mach AC only blow warm air?

If your AC blows warm air, common causes include low refrigerant, electrical issues, dirty filters/coils, defective capacitors, and faulty control boards. Methodically troubleshoot all likely issues before assuming the system must be replaced. Check refrigerant level, electrical connections, cleanliness of coils, and capacitance of capacitors, and inspect the control board for problems.

What should I do if my AC freezes up?

If your Coleman Mach AC is icing up or freezing, it’s likely due to restricted airflow over the coils. Turn the AC off and allow the ice to melt and drain. Thoroughly clean the fins and coils, straightening bent fins. Check for proper refrigerant charge. Make sure filters are clean and clear debris from coils. Monitor carefully when restarting to prevent freeze-up.

How can I tell if my AC compressor is bad?

Symptoms of a bad AC compressor include the unit not turning on, failing to cool properly, odd noises, high energy bills, and noticeable vibration/heating of the compressor itself. Have an HVAC technician diagnose the issue rather than guess. They can check refrigerant pressure, amp draw, and use gauges to test compressor function.

What maintenance should I do annually?

At least once per year, thoroughly clean AC coils/fins, check belt tension, lubricate fan motor if applicable, inspect the wiring for damage, check/recharge batteries, clean filters, test capacitors, and clear debris from exterior AC unit. Testing refrigerant charges and pressures can also prevent issues.


I hope this comprehensive AC troubleshooting guide provides useful tips to resolve your Coleman Mach air conditioner problems and get back to comfortable RVing. Remember to approach issues methodically, starting with easier DIY fixes before assuming major repairs are needed. And utilize RV repair professionals whenever necessary, especially for refrigerant charging and compressor issues.

With some basic maintenance and troubleshooting knowledge, you can quickly diagnose and fix many common AC problems yourself. Thanks for reading and let me know if you have any other RV repair topics you’d like covered! Wishing you many more miles of cool running air conditioning ahead!



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