The 4 fans of both, the MAX 1800 and MAX 2000.
There are 4 pieces of 12 Vold DC fans on one side of the chassis. You may replace them yourself with some skill. Dont touch the switched main power supply inside the MAXen. Getting them as a set is really expensive, but much easier to exchange.
You may need some skill too, to open the MAX and take of the 2 slot cage for the optional modemboards. You need to do that, otherwise you cannot take out the old fans. We did mount some fans with a hot glue pistol. It works fine, if you do not need to ship the unit to another destination. In that case, you need the original replacements.
This little fan is the source of the terrible noise of a MAX. It sounds like a 4 engine bomber aircraft from second world war, but there is no danger.
As long as it makes some noise, even terrible noise, it is running. That sounds good.
Take care when it is quiet ! Then you have very little time to do something against overheating.
The ELINA Model HDF 4012L - 12 HB is a 12V DC fan with 100mA and made in Japan.
The question is do we offer fan replacement service or do we ship lonely fans for your own exchange experience. We do not make acceptable profit with shipping fans, so we did give you all information, to buy your own choice. Dont take the cheapest Chinese brands, these fans will live less than 6 months and the down-time of the MAX to open and replace the fans is 1 hour 30 minutes at least.
Trust the experts, better to rent a MAX (here in Germany) for some days or some weeks or use your spare and prepare the replacement very well. We will support you, to save the config und load it onto the spare MAX for a downtime of some minutes.