Chemical Wash vs Chemical Overhaul: What's the Difference?

Many homeowners in Petaling Jaya use the terms “chemical wash” and “chemical overhaul” interchangeably, but they are actually two very different levels of service. Understanding the difference prevents you from wasting money on a service you don’t need or, worse, paying for a clean that fails to fix the problem.

We see this confusion almost daily at PJ Kool Aircond Service.

Most people don’t realise that Malaysia’s high humidity (often exceeding 80%) creates a specific type of buildup that standard cleaning misses. It is not just dry dust; it is often a thick, bacterial “jelly” that clogs your drainage system.

I am Ahmad, a senior technician here with over 15 years of hands-on experience. Let me break down the technical differences between these two services so you can decide exactly what your unit needs.

What Is a Chemical Wash (Canvas Method)?

A chemical wash, often called the “canvas method,” is a deep-cleaning process we perform with the indoor unit still mounted on your wall. This is the industry standard for annual maintenance.

The process relies on a heavy-duty canvas funnel and pressurised water to flush out contaminants without dismantling the entire machine.

Here is the exact 8-step protocol we follow:

1. Protective Funneling: We wrap a waterproof canvas or plastic sheet around the base of the indoor unit to catch every drop of dirty water.
2. Component Removal: Our technicians remove the front panel, air filters, and directional louvres to expose the coil.
3. Chemical Application: We spray a specific alkaline-based coil cleaner onto the evaporator coil.
   • Pro Tip: We avoid harsh acidic cleaners because they can strip the blue hydrophilic coating on your copper pipes, which eventually leads to gas leaks.
4. Soaking Time: The solution sits for 5 to 10 minutes, breaking down grease, mould spores (like Cladosporium), and compacted dust.
5. Pressure Flushing: We flush the coil with pressurised water, pushing the dissolved grime down into the canvas funnel.
6. Blower Cleaning: The cylindrical blower fan is cleaned in place using a brush and chemical spray to improve airflow.
7. Drainage Flush: We vacuum and flush the drainage pipe to remove the “jelly” biofilm that causes water leaks.
8. Final Check: The unit is reassembled, tested for airflow temperature, and the gas is topped up if required.

This service typically takes 45 to 60 minutes per unit.

For a unit that has been serviced within the last 12 months, this method effectively removes about 90% of surface buildup. It restores cooling efficiency and can lower your TNB bill by reducing the workload on your compressor.

What Is a Chemical Overhaul (Full Dismantle)?

A chemical overhaul is a “reset button” for your air conditioner. Instead of cleaning the unit where it sits, we completely remove it from the wall.

This service is necessary when the blockage is deep inside the machine, specifically on the back side of the evaporator coil or inside the drainage tray corners where a standard wash cannot reach.

Our full dismantle process includes these steps:

1. Total Removal: We pump down the refrigerant gas to the outdoor unit and remove the entire indoor unit from its wall bracket.
2. Complete Disassembly: We separate every single part: the evaporator coil, blower fan, drain tray, PCB board housing, casing, and fan motor.
3. Chemical Immersion: Key components are soaked in a dedicated chemical tank.
4. Two-Sided Coil Flushing: Because the coil is off the wall, we flush it from both the front and the back. This is critical because dust often impacts the rear of the coil, choking the airflow.
5. Blower Scrub: The blower fan barrel is fully submerged and scrubbed to remove caked-on black mould from every individual blade.
6. Biofilm Removal: We chemically treat the drain tray to kill the bacterial slime that causes foul odours.
7. Bracket Cleaning: The wall area behind the unit is wiped down and sanitised.
8. Re-installation: We remount the unit, reconnect the copper piping, and vacuum the lines to remove air pockets.
9. Performance Test: We refill the gas to the manufacturer’s specified pressure and test the cooling cycle.

This intensive process takes 90 minutes to 2 hours per unit.

The result is a machine that runs as close to factory-new condition as possible. You will typically notice a stronger wind flow and a fresher smell immediately.

When Do You Need a Chemical Wash vs an Overhaul?

Choosing the right service depends entirely on your unit’s history and current symptoms.

Choose a Chemical Wash When:

• Routine Maintenance: You have serviced the unit within the last year.
• Mild Symptoms: The air is cool, but the airflow feels slightly weak.
• No Strong Odours: You might smell a faint musty scent, but it clears up after a few minutes.
• Newer Units: The aircond is less than 5 years old and has been cared for.
• Prevention: You want to maintain peak efficiency to keep electricity costs down.

Choose a Chemical Overhaul When:

• Long Neglect: The unit has not been serviced for 2 years or more.
• Persistent Smell: There is a sour or “rotten” smell (often caused by dead skin cells and bacteria) that doesn’t go away.
• Zero Cooling: The air coming out is room temperature despite the compressor running.
• Visible Grime: You can see black slime or thick dust on the blower fan when the louvres open.
• Weak Airflow: Even on “High” fan speed, the breeze is barely noticeable.
• Failed Wash: You recently paid for a chemical wash, but the problem came back within weeks.

Pricing Comparison

Price is often the deciding factor, but remember that an overhaul involves significantly more labour and technical risk.

Here is how our rates compare at PJ Kool Aircond Service.

Service	Wall Unit (1.0-1.5HP)	Wall Unit (2.0-2.5HP)
Chemical Wash	RM160	RM190
Chemical Overhaul	RM250-350	RM300-400

Why the price difference? An overhaul requires a senior technician to safely pump down the gas and disconnect electrical wiring.

Improper reassembly by an unskilled worker can lead to water leaks or circuit board failure. We factor this expertise into the cost to ensure your unit is safe.

PJ Kool’s Approach: Always a Thorough Job

At PJ Kool Aircond Service, we prioritise honesty over upselling.

Our team follows a strict “diagnose first” policy. When we arrive, we check the airflow and inspect the blower. If a standard chemical wash will solve 90% of your problem, we will tell you.

We estimate that only 20% to 30% of the units we visit actually require a full overhaul.

The vast majority of cooling issues in Petaling Jaya can be fixed with a proper canvas chemical wash, provided it is done correctly.

Mr. Heng and I have serviced tens of thousands of units over our combined 35 years in the industry. We can look at the condition of your cooling coil and tell you within minutes if a dismantle is necessary.

When in Doubt, Start with a Chemical Wash

If you are unsure which service your aircond needs, I always suggest starting with a chemical wash.

This service solves the problem in roughly 80% of cases.

Our technicians will stop and alert you if they find the buildup is too severe for the canvas method—for instance, if the back of the coil is completely blocked. We will then discuss the overhaul option with you before proceeding.

This approach ensures you never pay for a premium service when a standard one would suffice. You will know the job is done right when you feel that crisp, cold air again.

Get in touch with PJ Kool Aircond Service to book your chemical wash or overhaul. We serve all areas in Petaling Jaya with transparent, fixed pricing and honest recommendations.