2001-2006 Mitsubishi Montero A/C Compressor: Rear A/C Woes & Failure Symptoms
This guide covers the critical compatibility differences, common failure symptoms, and replacement costs for the A/C compressor in the third-generation Mitsubishi Montero.
- For 2002-2006 models, you MUST verify if your Montero has rear A/C; the common replacement compressor is for models WITHOUT it.
- A seized compressor pulley can shred the serpentine belt, leading to a breakdown by disabling the alternator and power steering.
- When replacing the compressor, you must also replace the receiver/drier and expansion valve to prevent premature failure of the new part.
- A grinding noise that disappears when the A/C is turned ON often points to a bad pulley bearing, not necessarily a bad compressor.
Critical Compatibility Warning: Front vs. Rear A/C Systems
Warning: Before purchasing a replacement A/C compressor for a 2001-2006 Mitsubishi Montero, you must verify your vehicle's specific A/C configuration. Failure to do so will result in buying an incompatible part.
- 2001 Models: Compatibility can depend on the transmission. The most common compressor fits models with a 4-speed automatic transmission.
- 2002-2006 Models: The standard replacement compressor is for vehicles without rear air conditioning controls. If your Montero has a separate A/C control unit for the rear passengers, you will likely need a different compressor. Always double-check the part description and match it to your vehicle's options.
The correct compressor for most models is a Denso 10S17C style with a 7-groove pulley. Visually comparing your old compressor to the replacement part is highly recommended.
Symptoms of a Failing A/C Compressor
A failing A/C compressor in a Montero can manifest in several ways, from a simple loss of cooling to loud noises from the engine bay.
1. No Cold Air or Lukewarm Air
This is the most obvious symptom. When you turn on the A/C, the air from the vents is warm or not as cold as it used to be. This can happen suddenly or degrade over time. It indicates the compressor is no longer able to effectively pressurize and circulate the refrigerant.
2. Strange Noises from the Engine Bay
Unusual noises that start when you turn on the A/C are a major red flag.
- Grinding or Rattling: This often points to failing internal components or bearings inside the compressor. If the compressor is failing internally, it can send metal shavings throughout the A/C system, a catastrophic failure known as "black death."
- Squealing or Whining: A loud squeal when the A/C is engaged can be caused by a seized compressor pulley putting immense strain on the serpentine belt, or a worn belt slipping on the pulley.
- Noise When A/C is OFF: If you hear a grinding or whirring noise that goes away when you turn the A/C on, the problem is likely a worn-out A/C clutch pulley bearing. This bearing spins with the belt whenever the engine is running, regardless of whether the A/C is on.
3. A/C Clutch Does Not Engage
When you turn on the A/C, you should hear a distinct "click" from the engine bay as the compressor's magnetic clutch engages. If you don't hear this click and the center part of the pulley isn't spinning, the clutch is not engaging. This can be caused by several issues:
- Low Refrigerant: The system has pressure switches that prevent the compressor from turning on if the refrigerant level is too low, protecting it from damage.
- Failed Clutch Coil: The electromagnet that engages the clutch can burn out.
- Blown Fuse or Bad Relay: A simple electrical issue can prevent power from reaching the clutch.
- Excessive Air Gap: Over time, the space between the clutch plate and the pulley can become too large for the magnet to overcome.
Buying a Used 2001-2006 Montero A/C Compressor
A used OEM compressor can be a reliable and cost-effective alternative to expensive new parts, especially since many aftermarket options may not have the same durability. However, careful inspection is key.
What to Inspect Before You Buy:
- Verify Compatibility: First and foremost, confirm the part is from a Montero without rear A/C if you have a 2002-2006 model. Check that it is a 10S17C type with a 7-groove pulley.
- Check the Pulley and Clutch: Spin the outer pulley by hand. It should spin smoothly and quietly. A rough or noisy bearing is a sign of failure. The center clutch hub should be separate and not spin with the pulley.
- Inspect the Ports: The inlet and outlet ports should be capped or sealed. Open ports allow moisture and debris to enter the compressor, which can cause immediate failure upon installation.
- Look for Leaks: Inspect the compressor body for any signs of oily residue. A layer of grime mixed with oil indicates a potential leak from the case seals.
- Ask About Mileage: Whenever possible, choose a part from a lower-mileage vehicle. While compressors can last a long time, mileage is a general indicator of wear.
- Source Vehicle Information: A compressor from a vehicle that suffered a rear-end collision is generally a better bet than one from a front-end collision, where the compressor and condenser may have been damaged.
Pro Tip: When replacing the compressor, you MUST also replace the A/C receiver/drier (also called an accumulator) and the expansion valve. Failure to do so will void the warranty on most replacement compressors and can lead to premature failure of the new part. These components trap moisture and debris, and a failed compressor will have contaminated them.
Replacement Overview and Difficulty
Replacing the A/C compressor on a 2001-2006 Montero is a complex job that requires specialized tools and knowledge of A/C systems.
- Difficulty Rating: 4 out of 5
- DIY Feasible: Not recommended for beginners.
The process involves more than just unbolting the old part and bolting on the new one. The key steps include:
- Refrigerant Recovery: The R134a refrigerant in the system must be professionally recovered using a dedicated machine. Venting it into the atmosphere is illegal and harmful to the environment.
- Component Removal: This involves removing the serpentine belt, disconnecting the electrical connector, and unbolting the high and low-pressure A/C lines. The compressor itself is then unbolted from its mounting bracket.
- System Flush (Recommended): If the old compressor failed internally, the entire system should be flushed to remove metal debris.
- Installation: The new compressor, receiver/drier, and expansion valve are installed with new, lubricated O-rings. The correct amount and type of PAG oil must be added.
- Evacuation and Recharge: A vacuum pump is connected to the system to remove all air and moisture for at least 30-60 minutes. Finally, the system is recharged with the precise weight of R134a refrigerant specified for the vehicle.
Cost Comparison: New vs. Used
The cost to replace a Montero A/C compressor can vary significantly based on the parts you choose and who performs the labor.
| Part Type | Estimated Cost |
|---|---|
| New OEM | $800 - $1,300 |
| New Aftermarket | $175 - $450 |
| Remanufactured | $200 - $350 |
| Used OEM | $75 - $200 |
| Shop Labor | $370 - $550 |
Frequently Asked Questions
Can I just replace the A/C clutch and not the whole compressor?
Sometimes, yes. If the compressor itself is functioning correctly but the pulley bearing is noisy or the magnetic coil has failed, you can often replace just the clutch assembly. This is a more affordable repair, but it can be difficult to perform without special puller tools.
What is A/C "black death" and how do I avoid it?
"Black death" refers to the catastrophic internal failure of a compressor, which spreads black, metal-filled sludge throughout the entire A/C system. If this happens, simply replacing the compressor is not enough. The condenser, hoses, and evaporator must be thoroughly flushed or replaced to prevent the debris from destroying the new compressor. The best way to avoid it is to address compressor issues (like noises) early before it completely fails.
Do I need to add oil when installing a new compressor?
Yes. New and remanufactured compressors often come with a small amount of shipping oil that must be drained. You then need to add the correct amount of PAG oil specified for your system. Some compressors come pre-charged with the full system amount, but you must always verify by draining and measuring or checking the manufacturer's instructions. The total oil capacity is distributed between the compressor, condenser, evaporator, and drier.
My passenger side floor is wet. Is this related to the A/C?
Yes, this is a common issue on this generation of Montero, but it's not caused by the compressor. It's typically due to a clogged A/C evaporator drain tube. Condensation from the evaporator is supposed to drain out under the vehicle. When the drain gets clogged with leaves and debris, the water backs up and overflows into the passenger footwell. This can usually be cleared with compressed air or a flexible tool inserted into the drain tube from the engine bay.
Recalls and Technical Service Bulletins (TSBs)
As of this writing, there are no specific NHTSA recalls or widespread TSBs for the A/C compressor on the 2001-2006 Mitsubishi Montero. Recalls for this vehicle generation typically pertain to the brake booster, airbags, or fuel system.
Technical Specifications and Part Numbers
Compressor Type: Denso 10S17C
Pulley: 7-Groove
Known OEM Part Numbers: MR500877, MR568288
Cross-Reference Part Numbers: 471-1388 (Denso), 98338 (Four Seasons New), 97338 (Four Seasons Reman)
Technical Specifications
OEM Part Numbers: MR500877 MR5133448 MR568288 MR568290
Compressor Type: Denso 10S17C, Pulley Grooves: 7
We Have This Part in Stock
The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.
- Mitsubishi Montero:
- 🛍️ Shop This Part
- Critical Compatibility Warning: Front vs. Rear A/C Systems
- Symptoms of a Failing A/C Compressor
- 1. No Cold Air or Lukewarm Air
- 2. Strange Noises from the Engine Bay
- 3. A/C Clutch Does Not Engage
- Buying a Used 2001-2006 Montero A/C Compressor
- What to Inspect Before You Buy:
- Replacement Overview and Difficulty
- Cost Comparison: New vs. Used
- Frequently Asked Questions
- Recalls and Technical Service Bulletins (TSBs)
- Technical Specifications and Part Numbers
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