What does a chemical overhaul on a Mitsubishi Starmex involve?
A chemical overhaul takes the indoor unit off the wall and strips it to its evaporator coil, blower fan and drain pan, so every part is chemical washed and jet-rinsed, then refits it and vacuum-evacuates the pipes. On a Mitsubishi Starmex, it restores cooling when dirt is the cause, but not when gas or a part has failed. Key takeaways
- Dismantled, not on the wall: an overhaul takes the fan coil down; a chemical wash cleans it in place.
- Three units back to cooling: at The Nautical in Sembawang, three Mitsubishi Electric units that were not cooling were fixed this way.
- Evacuation is part of the job: the opened pipes are vacuum-evacuated before the refrigerant goes back in.
- Dirt is the target: if low gas or a failed part is the cause, an overhaul alone will not fix it. In the video above, Uncle Eric and the team carry out a chemical overhaul on a Mitsubishi Electric Starmex indoor unit. For a side-by-side comparison of all three levels of cleaning, see servicing vs chemical wash vs chemical overhaul; this post is about the overhaul itself.
Does your Starmex need an overhaul, or just a wash?
Work through these checks in order:
- Check the air filters. If they are grey and clogged, wash them and run the unit for a day. If cooling comes back, you only needed a clean.
- Look at the blower fan. Shine a torch through the air outlet. Black spots or a furry coating on the blades means mould and biofilm have built up deep inside.
- Look for water and smell. Leaking water or a musty smell on start-up usually means the drain pan and coil are coated too.
- Think back to the last wash. If a chemical wash on the wall did not fix it, or the problem came back within weeks, the build-up is deeper than a wash can reach.
- Rule out gas. If the filters, fan and coil look clean but the room still will not cool, the cause may be low refrigerant from a leak. That needs a leak check, not an overhaul. If steps 2 to 4 point to deep build-up, an overhaul is the right job. If your Mitsubishi leaks water as well and has never had a deep clean, a PowerJet wash may be enough first: see Mitsubishi aircon leaking water and not cooling. See the full price list for wash and overhaul rates.
Why do Starmex units end up needing an overhaul?
Starmex is Mitsubishi Electric's multi-split range, and it is everywhere in Singapore homes: one outdoor unit on the ledge running two, three or four indoor units. The bedroom units often run every night for years. In our humid climate, that adds up. Dust that slips past the filters sticks to the wet coil fins. Mould and slime grow on the blower fan and in the drain pan. Over time, airflow drops, so the room takes longer to cool or never gets cold; water backs up in a clogged drain pan and leaks; and the unit starts to smell musty when it switches on. A normal service cleans the filters, the front of the coil and the parts you can reach. When the build-up is deep inside the coil and behind the blower fan, the only way to get it all out is to take the unit apart.
What do we do in a Starmex chemical overhaul?
Every job is different, but the core steps are the same:
- Check the system first. We note how the unit is cooling and look for other faults, so we know what the overhaul is expected to fix.
- Pump down and disconnect. The refrigerant is pumped back into the outdoor unit, and the indoor unit is disconnected and taken off the wall.
- Strip it down. The casing, drain pan and blower fan come off, leaving the coil.
- Chemical wash. The coil, blower fan and drain pan are treated with cleaning chemical to break down grease, dirt and biofilm.
- PowerJet rinse. Our high-pressure jet wash flushes everything out of the coil fins and the fan blades, a far deeper clean than a wipe and spray.
- Dry, reassemble and refit. The unit goes back on the wall and is reconnected at the flare joints.
- Leak check. We test the joints for leaks.
- Vacuum evacuation. Because the pipes were opened, we evacuate the indoor unit and piping before releasing the refrigerant back in. Our post on why evacuation matters explains why this step is never skipped.
- Release the gas and test run. The refrigerant goes back in, and we check cooling and drainage. If you are worried about chemicals near your aircon, we answer that separately in is a chemical overhaul safe?.
The Nautical, Sembawang: three units not cooling
At The Nautical condo in Sembawang, three Mitsubishi Electric units were not cooling. All three were fixed with a PowerJet chemical overhaul. watch: 3 Mitsubishi units at The Nautical fixed by chemical overhaul This is a pattern we see often on multi-split systems. When several indoor units lose cooling together and the outdoor unit and gas are fine, the cause is usually dirt in each indoor unit, built up over the same years of use.
What about the outdoor unit?
The outdoor unit also collects dust, leaves and grime on its condenser coil, and a choked condenser cannot get rid of heat properly. We check it during an overhaul job and wash it only when it needs it, at extra cost. On an earlier PowerJet chemical overhaul of a high-capacity Mitsubishi Electric GE24VA, the difference on the outdoor unit was clear after only the first wash. The before-and-after difference on an overhauled Starmex can be striking. watch: PowerJet chemical overhaul restores a Mitsubishi aircon
What it costs
Job | Price | What drives it |
|---|---|---|
Chemical overhaul, 1 wall unit | S$180 | Unit size (BTU), how dirty it is, access to the unit and the ledge |
| Chemical wash, 1 wall unit (for comparison) | S$120 per unit | Heavy-duty coil cleaner, if advised on site, is an add-on from S$30 | Every chemical overhaul includes a free gas check and top-up (worth S$165) and a deep evacuation (worth S$395). Washing the outdoor unit, when it needs it, costs extra. Every service includes a 90-day warranty. After an overhaul, regular premium servicing with PowerJet keeps the coil and blower fan clean so the build-up never gets deep again.
When to call a technician
Book a check if your Starmex:
- takes much longer to cool the room than it used to, or never gets cold
- leaks water even after normal servicing
- smells musty when it switches on
- has black spots of mould visible on the blower fan through the vents We will tell you honestly whether it needs a chemical overhaul, a chemical wash or just a good service. Book online in under a minute, or ask Luna, our AI assistant, on WhatsApp at any hour.
Frequently asked questions
How long does a chemical overhaul on one Starmex indoor unit take?
At least 45 minutes to an hour or more per unit, because the unit is fully dismantled, washed and refitted, and the system is evacuated afterwards. The exact time depends on the unit and how it is installed.
Do all the units on a Starmex system need an overhaul at the same time?
No. Each indoor unit is assessed on its own. Often only the bedroom units that run every night need an overhaul, while a living room unit used less is fine with a chemical wash or normal servicing.
Does the aircon need a gas top-up after a chemical overhaul?
Not normally. The refrigerant is pumped down into the outdoor unit and the opened pipes are evacuated before it is released back, so the charge stays in the sealed system. We check the gas after every overhaul and any top-up is included free; a large shortfall points to a leak, which is repaired first.
How often will a Starmex need a chemical overhaul?
There is no fixed interval. It depends on hours of use, dust, cooking and how regularly the unit is serviced. Good regular servicing stretches the time between overhauls.
Is a chemical overhaul covered by the 90-day warranty?
Yes. Every iAircon service, including a chemical overhaul, comes with a 90-day warranty, and any flare joints we remake during the overhaul are covered.
Eric Lim, aka Uncle EricFounder of iAircon.Repair, now in its 10th year servicing aircons in Singapore. Every job is filmed, so you can watch the work on YouTube.
