Restoring a Webasto NiteCool TCC-100 evaporating cooler

I had to restore an old evaporating cooler on a RV. Since I was not able to find any help on the web, here's a post to explain the process.

What is an evaporating cooler ?

An evaporating cooler is a air conditioning unit that's not using a refrigerant gaz and a compressor to cool air. Instead, it's using a very simple effect based on the physic of dew point. When some dry and hot air goes through a humid environment, it captures water until it's saturated with humidity (so called the dew point). When water capture evaporates from liquid to gas, a huge amount of energy is required (latent energy of water is very high) and this energy is extracted from the air's temperature.

The humid air is then cooler than the initial dry air.

An evaporating cooler is a system using this principle to operate and cool a limited volume. It's not as efficient as a refrigerant based cooler (you could only expect a cooling factor of ~5°C), but it's using a small fraction of the energy required to operate such system. This is perfect for a mobile vehicle that can't be plugged on main grid to cool. For operating such system, only 5W to 150W is required (depending on the required cooling factor), that is: running the main system fan.

Webasto NiteCool TCC100

While Webasto is now making and selling refrigerant based air cooling unit, they used to produce and sell evaporating coolers. NiteCool TCC100 is one of them.

Webasto NiteCool TCC100

You can find its manual here and its installation procedure.


This product is really well made. I've opened it completely down to the electronic boards and I must say that it's manufacturing quality is very high. The PCB are varnished to limit corrosion, everything is perfectly fitting and well labelled. There are only few issue with the system and I'll explain them below.


When I bought the RV the unit was already installed. I suppose it was mounted around 2006/2008 but it seems it wasn't maintained at all since. So here's the process I've followed to restore it to pristine conditions:

Step 1: Open the exterior cover

You'll need to walk up the roof and remove all 6 Torx screws to open the exterior cover.

You'll then clean the cover carefully like this: Cleaned cover outside

and interior:

Cleaned cover inside

Step 2: Extract the evaporating cardridge

Then, inside the cover, you'll find the wood's fiber that are soaked with water and some foam used to isolate and close the air flow so that it's going through the wood. On my system, it's was completely going to dust, so I had to replace it. Hopefully, everything is well made so you can remove the cartridge (unplug the plastic tubing) and continue the cleaning process while the part is being delivered to you.

Underneath the cartridge, you'll find this: Exterior cover and cartridge removed

You'll clean it first: Cleaned system The working principle of this system is to pump up water from a reservoir in your RV up to a small reservoir on the roof (the part with the black oval cover on the previous picture). Then the water is pumped from this second reservoir into the cartridge. On my system, it wasn't pumping water from the first reservoir to the second reservoir.

So I had to inspect the water sensor (follow the black cables). One of mine was completely corroded: Corroded sensor

Here's the only defect I've found from this system: They are using resistance based water sensing and they are using a high voltage (5V I think) for this. At this voltage level, the 2 metallic probes in the system will start making water electrolysis if it's not pure (and it's not pure). A capacitance based sensing would have avoided this and wouldn't have made the electronic much more complex.

Anyway, to mitigate the electrolysis issue, they provided an additional wire connecting the ground voltage to the main water reservoir. Since only one pin is required for this, I swapped this wire with the bad sensor (making sure the connection is correct).

The good wire/sensor looks like this: Non corroded sensor

I wasn't able to find the same sensor anywhere. If you know where to source it, please comment below.

Step 3: Clean and replace the cardridge foam

I haven't took any picture of the dirty cartridge, so I'll just describe it. It was very dirty and the foam was crumbling to dust when touched. I've removed it and removed the double side tape maintaining it and used IPA to clean the plastic. I've measured the foam size and, hopefully, found a supplier for this exact foam dimension (see below for the link). I've also removed the plastic tubing and cleaned it with a air compressor. Remounting is the same as unmounting, but in reverse.

The clean cartridge looks like this: Cleaned cartridge without foam

You'll then stick the foam (that will inflate by itself over the next hour) and get this: Complete cartridge

And install the system back on the roof, plugging the plastic tubing back: Reinstalled cartridge

You can mount the cover back and you are done!

Step 4: Inside cleaning

Cleaning the internal part is very simple, but tedious. You'll need to unscrew the external cover and then the internal one. You'll need long and thin tools for this since screws are inside thin cones.

Once cleaned, you'll simply reassemble the system back to work: Interior part cleaning

If you need it, I've made a pinout of the connectors for this system, please ask in the comments below.

Finally, you'll put some chlorine in the big reservoir and let the system run for 2 hours at full speed. You'll need to monitor it's working as expected:

  1. It should light on slowly (progressing fan acceleration and stopping)
  2. It should pump the big reservoir once and stop few secs after (if not, power it off and check the water sensor, see above)
  3. You should hear the second pump running at regular interval
  4. Going back 2h later, you should feel the RV is cooler and a lot more humid.

Previous Post Next Post

Sponsored links

In order to pay for infrastructure cost for this blog, I'm listing some affiliated links about the hardware listed above.