Intermittently, I get a mildew odor when the AC first kicks on in my ‘22 ES350 UL, especially after the car has sat overnight. It seems to disappear in a few moments. I have occasionally encountered this in other cars over the years and it was helped with some Lysol spray into the air intakes, but in his case it doesn’t seem to change. I know there are some messy and expensive cleaning procedures from the dealer or others but it’s not that bad (and hopefully won’t be). Our weather has been humid and rainy lately which is probably connected.

Anyone had this issue as well? Any suggestions? I only have less than 5K on odo and at her annual service in April the cabin air filter was not replaced… can that hold odor or mildew as well?

Thanks.

 

AC units dehumidify the air they circulate by allowing condensate formed on the evaporator to collect and drain from the evaporator compartment. In a car, you will see water drip on the ground under the car, easiest seen if the car is parked and running on a hot humid day. There may be a rubber nipple that acts as a check valve to let water out of the evaporator compartment and prevent air from entering through the drain. If the drain opening for that condensate is partially plugged, water can be trapped in the air passage and get moldy. So the first thing to check is that the condensate is draining properly. If that rubber nipple-like thing can be found (directly above the puddle of water on the ground) and inspected, check it out. The next thing I would try is to remove the cabin air filter. Sniff the filter. Take a good look at the area where the filter fits and see if there is visible mold that you can wipe out with Clorox cleaner on a rag. Install a new filter, perhaps a low cost one from Amazon, and see if the odor is improved. Last resort for me would be to ask the dealer for advice, but they may know exactly what to look for.

I had my semi-annual home HVAC system service a couple months ago and the technician showed me the sump in the condensate pump was contaminated with mold or something ugly. He put Clorox and clean water in it and flushed it out a few times. Have you heard of Legionnaire's Disease? The bacteria can accumulate in stagnant water.

https://pubmed.ncbi.nlm.nih.gov/19379540/

 

Had the same issue but was able to get rid of it with vinegar/water spray into air intake while inside vents were sucking it in. Did it twice.

 

good idea! I would think any type of mold killer sprayed into the INTAKE side or the AC system would work.
The first reply responder had a very accurate explanation and suggested cures.

Another reason we are seeing more "smells" from the AC is because the Refrigerant amount is less than years past, so the manufactures design the cooling coil has to be more efficient by having more cooling fins and closer together. Closer fins tend to hold the condensation water. This creates a dampness and hence, Mold.

I had heard another way to combat this "collection of water" is to switch on the AC fan to HIGH before switching off the AC System, car. I would guess this is to help Blow the condensation out of the cooling coils..

 

A simple solution that works for me is to spray Lysol into the air vent. Before spraying AC should be in coldest setting and outside air circulation. Run the AC full speed for several minutes. After running keep the windows open for several hours. I do this several times a year for both my cars and never had smell issue.

 

There's a Technical Information Service Bulletin (TB) L-SB-0003-20, HVAC Odor Maintenance, (pdf) which lists several steps which may help reduce orders. The steps are:

 

Get this:

https://autoparts.toyota.com/product...kit-00289acrkt

 

I watched a video from the Car Care Nut and he said the same thing about using fresh air rather than recirculating all the time. I’m getting a new cabin filter and will redo the Lysol treatment. The Toyota AZC cleaner is good stuff, and that’s what the CCN showed, but the problem seems to be that in order to use it you may have to lift the car to inject the main cleaner through the drain line as it is hard to access with the car just parked normally, not something I can do (he was doing an LC, not an ES so I’m sure ours it in a different spot but not necessarily easy to access). Hopefully with the Lysol, new filter and using more fresh air mode I can avoid a trip to the dealer for a cleaning job.