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

You know that sticky, humid feeling when you walk into a room in Kuala Lumpur and realise your aircond is running but not actually cooling.

It is frustrating.

Then you call a technician, and suddenly you are choosing between a “chemical wash” and a “chemical overhaul.”

These terms sound identical to most homeowners.

There is actually a massive difference in the work involved and the price you will pay.

Understanding this distinction prevents you from overpaying for a service you do not need.

We see this confusion every day at PJ Kool.

Our goal here is to break down exactly what each service entails so you can make the right choice for your home.

Chemical Wash: The Deep Clean

A chemical wash is a thorough cleaning of your aircond’s internal components using a specific alkaline or acidic solution.

Think of this as a “spa day” for your unit that goes far beyond standard filter cleaning.

In Malaysia’s high humidity (often exceeding 80%), dust mixes with moisture to create a stubborn “jelly” or biofilm on your coils.

Water alone cannot remove this biological buildup.

What’s Involved in a Chemical Wash

We follow a strict protocol to ensure safety and cleanliness during this process.

1. Protective preparation: The technician removes the front panel and filters.
2. Water containment: A large, custom-fitted canvas bag is wrapped around the unit to catch every drop of water and chemical runoff.
3. Chemical application: We spray a specialized chemical solution onto the evaporator coil to dissolve the stubborn “jelly” and grime.
4. Pressurised flushing: A high-pressure water jet washes away the dissolved dirt without bending the delicate aluminium fins.
5. Component cleaning: The blower wheel and drainage tray are scrubbed to remove mould spores.
6. Drainage clearance: Technicians use a vacuum or pressure pump to clear the drainage pipe and prevent future leaks.
7. Gas check: We measure the refrigerant pressure and top it up if it is slightly low.
8. Final test: The unit is reassembled and tested for airflow and cooling speed.

The entire process takes about 45-60 minutes per unit.

The key distinction here is that the unit is not fully dismantled.

The evaporator coil stays on the wall during the cleaning.

When to Get a Chemical Wash

You should consider this service if you notice specific performance dips.

• The “Jelly” Factor: You see a clear, slimy substance in the drain pan (very common in the Klang Valley).
• Reduced Airflow: The fan is running at full speed, but the air coming out feels weak.
• Mild Odours: The air smells slightly musty, like damp socks.
• Time Lapse: It has been 6 to 12 months since your last professional service.
• Efficiency Drop: Your TNB bill has crept up because the unit is working harder to cool the room.

Chemical Overhaul: The Complete Teardown

A chemical overhaul is the most intensive restoration procedure available for an air conditioning unit.

Technicians completely dismantle the indoor unit to remove the evaporator coil from the wall.

This allows us to clean areas that are physically impossible to reach while the unit is mounted.

What’s Involved in a Chemical Overhaul

This process requires a higher level of technical skill to avoid damaging the copper pipes or gas system.

1. Gas Pump Down: We pump the refrigerant gas back into the outdoor compressor to save it (avoiding a total waste of gas).
2. Full Dismantling: The indoor unit is taken off the wall entirely.
3. Component Separation: The evaporator coil, electrical circuit board (PCB), and fan motor are separated.
4. Chemical Soaking: The coil is submerged in a chemical bath for 30-60 minutes to eat away deep-set corrosion and compacted dust.
5. Detailed Scrubbing: Every individual part, including the fan blades and housing, is scrubbed clean.
6. Drainage Flush: We flush the drainage system completely to ensure zero blockages.
7. Reassembly: The unit is put back together with precision.
8. Vacuum & Recharge: The system is vacuumed to remove moisture from the copper pipes before releasing the gas back in.
9. Calibration: Technicians test the gas pressure and running current (amps) to ensure it matches the manufacturer’s specs.

A chemical overhaul takes 2-4 hours per unit.

It resets the unit to a near-factory state of cleanliness.

When to Get a Chemical Overhaul

This service is a repair solution rather than just maintenance.

• Severe Neglect: The unit has not been serviced in over 12 months.
• Zero Airflow: The cooling coil is so clogged that air cannot pass through it at all.
• Persistent Leaks: Water is dripping profusely because the back tray (which cannot be reached during a normal wash) is blocked.
• Foul Odours: There is a strong, dead-animal or rotten smell indicating severe bacterial growth.
• Corrosion: Visible oxidation or rust on the evaporator fins.
• Failed Wash: You already paid for a chemical wash, but the problem came back within two weeks.

Side-by-Side Comparison

Making the right choice depends on the severity of the issue.

Feature	Chemical Wash	Chemical Overhaul
Coil handling	Cleaned in place (on wall)	Fully removed and soaked
Cleaning intensity	Surface & between fins	100% deep pore cleaning
Dismantling	Partial (covers/filters)	Complete teardown
Time required	45-60 minutes	2-4 hours
Gas handling	Top-up if needed	Pump down, vacuum & recharge
Bacterial removal	High	Maximum (Chemical Bath)
Price range	RM80-180	RM200-450
Best for	Yearly maintenance	Resurrection of dead units

Price Comparison in Malaysia (2026)

Prices have adjusted slightly in 2026 due to rising material and transport costs in the Klang Valley.

We believe in transparency so you know the market rate before booking.

Unit Type	Chemical Wash	Chemical Overhaul
Wall-mounted (1.0-1.5 HP)	RM80-150	RM200-350
Wall-mounted (2.0-2.5 HP)	RM100-180	RM250-400
Cassette (Ceiling)	RM150-250	RM350-550
Ceiling Concealed	RM200-350	RM400-650

These ranges cover most areas like PJ, KL, Subang Jaya, and Shah Alam.

Condominiums with difficult access or strict management hours may incur slight surcharges across the industry.

Which One Do You Actually Need?

You can often diagnose this yourself with a simple torchlight check.

Shine a light into the air outlet where the air blows out.

Choose Chemical Wash If:

• You can still see through the blower fan blades, even if they are dusty.
• The unit is cooling, just not as cold as it used to be.
• You have serviced the unit within the last 6-8 months.
• There is no heavy “jelly” buildup on the coils.

Choose Chemical Overhaul If:

• The blower fan is so caked with dust you cannot see the individual blades.
• The unit is “sweating” or dripping water from the back near the wall.
• The air smells sour immediately upon turning it on.
• You are reviving an old unit in a rental property that has sat idle for months.
• Another technician already did a chemical wash and it failed to improve airflow.

Mr. Heng’s Professional Recommendation

Mr. Heng has serviced thousands of units across Damansara Utama and PJ, seeing every possible AC disaster.

His advice is grounded in saving you long-term costs.

For most residential units: A chemical wash once a year is usually perfect.

Most homeowners find that pairing this with a standard filter cleaning every 3 months keeps the unit running efficiently for years.

For neglected units: If you have skipped service for over 18 months, do not jump straight to an overhaul.

Start with a chemical wash assessment.

We solve about 70% of “severe” cooling issues with a proper, meticulous chemical wash.

For very old units (8+ years): Sometimes an overhaul reveals that the copper coils are too corroded to save.

In these specific cases, spending RM400 on an overhaul is a waste of money when a new aircond installation costs RM1,200.

We will always tell you if replacement is the smarter financial move.

Don’t Overpay for Services You Don’t Need

Unethical providers sometimes push for an overhaul because it commands a higher price tag.

They might claim your unit is “blocked” without showing you the evidence.

At PJ Kool, our technicians are trained to show you the grime before recommending a solution.

If a chemical wash is enough to get you freezing cold air again, that is all we will recommend.

Integrity keeps our customers coming back.

Get an Honest Assessment

Are you still unsure which service is right for your specific situation?

You don’t have to guess.

Send us a clear photo of your indoor unit (with the flap open) on WhatsApp at 012-2252 623.

We can often spot the difference between surface dirt and deep clogs just from a picture and give you a straight answer.

Learn more about our chemical wash service and the specific steps we take to protect your home.