We clean a bunch of kitchen condenser coils... what a mess. I don't do steam anymore. It seems to make matters worse.
I use Foam'n Clean cut by 70% water. Let it sit on a powerless condenser for 5 minutes then hose the crap out of it. Hot water works best but cold works too. Rinse WELL !!. It works great but don't spray controls or fan motors. Condenser fan motors will crap out that day or the next.
If a top mounted condenser is cleaned then tilt the reach in to the back. We use a 2 ton hydraulic floor jack. The cleaner and water will rush to the back of the box. If it is allowed to run down the sides or front it will stain the dull aluminum, even the front stainless will streak.
We then use a small shop vac to suck the dirty water off the floor and follow up with a clean water mop. It's not an easy job. If you don't get the soap water off the floor someone could slip and fall. You must warn all who enter the kitchen.
If bi-monthly or even quarterly PM are contracted then buy a flat sheet of 3/16th foam window shaker black filter pads. Cut to fit the entire coil. Use jumbo paperclips to hold the pad by pushing the double end through the pad and slide onto a condenser fin. Do this on all 4 corners or just the top two. You can wash the filter pad on the next PM through the dishwasher or mop sink. Dry them by shaking and put them back on. DO NOT leave them on without cleaning them for longer than 90 days.
DO NOT USE ROLL TYPE FOAM (open cell) FILTER MATERIAL. The thickness was changed a few years back and is too restrictive now. The compressor will over heat on blend refrigerants. When the roll type is used and as it ages it will stiffen up and make it useless. Use the single sheets only. The poly hair filter material (blue and white crap) is about as useless as a tit on a bore-hog. Waste of time and money.