Trav-L-Cool Air Conditioner – Explanation and Servicing

Trav-L-Cool air conditioning system

Like a number of old vans (and possibly some new ones!) our Hymer B544 came to us with a Trav-L-Cool air conditioning system installed. These are ‘evaporative’ coolers so work differently to compressor driven air conditioners like you would find in cars and offices everywhere.

Compressor based air conditioners work on exactly the same principle as a domestic fridge but are configured to remove heat from the air in your room (or car) and transfer that heat to the outside air, as opposed to transferring heat energy from the inside of the fridge to the outside of fridge. Evaporative air conditioners work by the principle that when water evaporates it removes heat from it’s surroundings, the same effect that causes your skin to feel cold if it is wet and you blow on it.

Being an engineer I felt compelled to take the Trav-L-Cool apart to see how it works, and decided to give it a once-over while I was at it………….

The Trav-L-Cool system consists of two main units, the roof mounted box and an internal tank/pump.

This is the roof mounted unit, which sits on a cut-out in the roof with vents & controls on the inside of the van:-

This is the outlet vent and controls mounted on the inside of the van directly underneath the main unit:-

In our van the tank and pump are mounted inside the wardrobe:-

The basic principle of the system:

Water is pumped up to the roof unit where a fan draws air through a stream of water (to cool it), through a filter (which is also wet) and down into the van. Excess water is returned to the tank. The system is not sophisticated but it is reasonably effective, with the main benefit over compressor based air conditioning being that it does not use much electrical power – the whole system runs off 12V so it can be used when mains electricity is not available. 

The system can also be used as a big extractor fan – the fan is reversed and the pump stopped so air is simply sucked up out of the van and discharged out of the roof unit.

One thing to be aware of is that compressor based air conditioners remove moisture from the air as they operate, whereas the Trav-L-Cool system actually adds moisture to the air, so it is not as effective if it is very humid outside and you need to have a window opened slightly to allow air to circulate, otherwise you could end up with condensation forming on the inside of the van if you run it for many hours.

Stripping and cleaning the unit:-

The top of the unit is held on with a few screws, simply remove these and the cover lifts off (you will find a tube connecting the top to the rest of the unit, you will need to pull this off to remove the top completely) revealing the filter unit within:-

The metal disc you can see on the top of the filter is attached to the fan so spins when the unit is operated, the water that is pumped up from the tank is sprayed onto this disc which then flings it off in all directions! The filter is the big bit under the white disc, sat in a large black plastic bowl thingy.

This is the underside of the lid, you can see the tube mentioned earlier and the nozzle that sprays water onto the disc. The water coming off the disc in caught by the back plastic bit and then runs down into the bowl that the filter sits in (kind of like a mini waterfall surrounding the filter)

The result is that the air drawn through the filter passes through this waterfall of water, cooling it down. The filter also absorbs water from the black plastic bowl so it is kept constantly wet while the unit is working.

After a few years of use the filter will be full of junk I took it out to clean it. To do this simply remove the three screws holding the metal disc in place and put the disc to one side. You can then remove the screws from the white plastic disc on top of the filter and lift the whole filter assembly out. I cleaned the filter by blowing the dust out with compressed air and then thoroughly rinsing the filter in clean water.

With the filter out you can see the fan itself (the small component connected to the red wires is a resistor that drops the voltage to the fan motor when low speed is selected):-

There was a reasonable amount of silt that had collected in the bottom of the bowl, and a lot of general grime everywhere. A quick clean up had it looking like this:-

The mesh that stops insects etc getting into the unit is fixed to the housing with rivets, and on inspection a few had failed leaving gaps around the mesh:-

Some small nuts and bolts quickly fixed that:-

After that it’s just a case or reassembling everything in the reverse order and the unit is ready for another few years of good service!

All of this is very easy to do with a few simple hand tools and an hour or so of time, so if you have one of these on an older van it is probably well worth the time to give it a clean out…….

Any questions, please leave me a comment below

If you want to know more about Evaporative coolers generally, Wikipedia has some good information here:-

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  1. très interressant mais à quoi sert le bouton pompe sur l’appareil quand j’appuie dessus cela gargouille . point
    j’ai exactement le même trav L cool
    je viens d’acheter ce camping car l’ancien me dit ne jamais sans servir ?

    • Dan

      July 16, 2019 at 7:02 pm

      Hi Claude – the pump button on the device turns the electric pump on to pump water from the reservoir up to the roof mounted cooler. The gurgling noise will be water being pumped. The fan will run without the pump but if you want the cooling effect you need to have the fan blowing into the van and the pump running. Hope this helps! Cheers, Dan

    • Dan

      July 16, 2019 at 7:03 pm

      Bonjour Claude – le bouton de pompe de l’appareil allume la pompe électrique pour pomper l’eau du réservoir jusqu’au refroidisseur monté sur le toit. Le gargouillis sera de l’eau pompée. Le ventilateur fonctionnera sans pompe, mais si vous souhaitez un effet de refroidissement, vous devez le faire souffler dans le fourgon et faire fonctionner la pompe. J’espère que cela t’aides! À la vôtre, Dan

  2. Hi there… great to hear of someone who actually knows of this product. We have this unit fitted to our S555 and are in dire need of a filter. any ideas would be vey much appreciated.

  3. thanks for the very handy advice

  4. Only just found this and it encouraged me to go service outs, do you a copy of the manual?

    • Dan

      May 23, 2020 at 8:31 pm

      Hi Grant – I’m afraid I don’t have a manual (I never managed to find one). I just resorted to working out how it works by taking it apart! 🙂 Cheers, Dan

  5. Roger Matthews

    May 24, 2020 at 10:53 am

    Hi Dan…….. again, sorry for long delay.. Thanks also for your thoughts. It is a bit of an ongoing problem made worse by the situation as it is now . Hey ho, I just have to wait.!!!
    Still not solved the filter problem yet. I have now looked properly at the picture in your original response. I don’t remember having the white disc. Will get up on the roof later today. Now also a bit difficult to get out to view anything.
    BUT we can only keep smiling…. Best wishes to you… keep well.
    Best wishes Roger

  6. Does anyone know the flow rate of the pump as I need a new one.

  7. Hello,
    I have the same system mounted on the used motorhome I bought, except it is not working. The fan does not work and the pump doesn’t run either.
    I removed the panel with the switches and saw three cables : one + going to the + of the auxiliary battery, and two (- and pump) going to the pump.
    Do you know if the wiring is similar on your unit ? Or maybe an idea on what is wrong with mine ?
    There is not much info on this on the internet, due to its age.
    Thank you very much,

    • Dan

      May 31, 2020 at 12:53 pm

      Hi Remi – You should have at least a ground (-ve) connection also going to the Trav-l-Cool unit (though it may not go switches) The fan and pump are then switched from the roof unit, via a resistor for the low speed setting. If neither the fan or pump are working on your unit I would check the incoming power first – make sure you have 12v and a good ground to the roof unit. If not, trace the wires back and look for damage, disconnection or a blown fuse. Hope this helps, Cheers, Dan

      • Roger Matthews

        May 31, 2020 at 1:29 pm

        Good advice Dan, well done. Good luck to Remi. Still have not been able [physically] to get on the roof yet…… Best wishes Roger.

  8. trav-l-cool manual can be found here, it’s in German but quite easy to understand or translate with google. Good luck

  9. Hugo Oliveira

    June 11, 2020 at 6:52 am

    Hi Dan, very nice article. Thanks for that!!
    I also bought a B544 with this cooler and will clean it up as you suggested.
    Notice that when I turn on the pump on the cooler it splashes a bit of water. Is that normal or should I replace the filter?
    Plus, there might be a electric problem because for any reason sometimes when turning on the cooler the pump fuse on the main unit of the camper burns out.
    Any advise will be very welcome. Cheers. Hugo

    • Dan

      June 11, 2020 at 11:41 am

      Hi Hugo – there shouldn’t be any water splashing when the system is operating – is this coming out of the roof unit or from the pump/water reservoir? If it is the roof unit you should be able to identify the problem once the top cover is removed – you can run the system and see if any water leaking out of somewhere it is not supposed to!
      Regarding the electrical issue it may be that your pump is partially seized, so is presenting a high electrical load when switched on. Does the pump fuse supply just the Trav-L-Cool pump or also other circuits on the vehicle?
      Hope this helps, Cheers, Dan

      • Hugo Oliveira

        June 12, 2020 at 7:59 am

        Thanks Dan. Thanks a lot for your help. I’ll figure it out and let you know if the problems persist.

  10. Hugo, the water return from the cooler works on a Venturi effect. If there is even a small blockage in the scavenge pipe it will allow the water level to increase so make sure these are all cleaned.
    Mine was also blowing the hab fuse, turned out to be my pump was on the way out and drawing too much current. I tried various pumps before sourcing an original and approx 3-4 lpm worked ok, any less and the Venturi effect wasn’t enough to draw water bank to the tank.

    There should be a few drain holes in the bottom cover that should prevent water ingress into the camper, these can become blocked so check.

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