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I run my fish room on mostly Eheim filters and heaters. Recently I have been servicing old filters and trying to get dud ones working, I have a bunch of old thermofilters, three professional 1 and a professional 2, I would love to get the heating capability working, so I bought new controllers through Aquaristik Shop in Germany. My problem is the controllers work only on series 4 heater units, my units are either without a series number or series lower than 4.
Has anyone come across this problem and is it solvable, I would be greatful for any advice?

I have had exactly the same problem. I used an inline hydro heater as it looked like the replacement part was the entire filter head.

Jools

The filter heads are fine, motors working and impellers are replaced.
The problem is the heating unit at the base of the filter body, they are controlled by an external thermostat unit with a probe, these new units are fine with heaters with a series number starting with 4 but units lower than 4 are not comparable...
Strangely I have an ancient classic model Eheim Thermofilter that has been running for about 15 years without any problems.

I know those inline heaters they seem quite popular they seem a bit flimsy to me, don't understand why there are not more external heating options...

I have 3 Eheim Pro II running and two more on the shelf. The bigger one is due to go into operation this summer. None are the thermofilter models. I chose to us the Hydor inlines. I have two Eheim 2026 running fine after 12-13 years and a third for about 9 months. I have thee Hydor inlines, one on each Eheim, and the heaters were all hooked up when each Eheim went into service save the first which went on in year two. I wanted to get the heater out of the display tank.

I chose specifically to avoid the thermofilter models. For one, space taken by a heater means less space for media and/or water. Next, I can deal with a Hydor malfunction by unplugging it and adding an internal heater to a tank. Very fast and easy and I could even not ever remove that inline heater despite not using it. Also the heaters in the filters are designed specifically for either fw or sw (or the used to be). I keep all fw tanks. But sometimes I resort to salt as a medication. Hmmm.

In your situation, I would try to return the stuff you bought and exchange it for Hydor inlines. You will not regret it, imo. Realistically, we buy filters top help clean the water and make it safe, usually by hosting mocroorganisms. We do not buy them as a way to heat the water, that is another matter. But the fact that I have a couple 11-12 year old working Hydors and your Eheim heaters are not working says a lot to me. This is one of the very few things I have seen from Eheim that I think were a mistake. The initial problem with the filters leaking from the head were diagnosed and fixed very early on in the life cycle of the Pro IIs. The heaters always seemed to be problematic.

Anyhow, just my 2 cents worth, or should I say two gallons?

I remember the old Thermofilters when they were in the U.S. Never really caught on here. The cost difference between the base model filter and the thermofilter was huge. Several times the cost of a traditional heater or even an inline heater.

I bought a used 2126 recently. I knew the heater wasn't working, but I got a deal, so was fine with it. It's a fine filter. I suppose I could add some foam to the bottom of the filter where the heater element is, but I haven't bothered to do that yet.

Of course, this doesn't solve your problem, but they are good filters, even without the heater working.

Thanks to all, these were largely second hand filters so they were a bargain but I expect more from Eheim, and there is no excuse there are countless cheap options for filters out there if you buy a premium production it unreasonable to expect back up? As it is I have heaters to spare, but I do love good technology... Why shouldn't you be able to filter and heat at the same time?

Gerald CapeTown wrote:Why shouldn't you be able to filter and heat at the same time?

TwoTankAmin wrote:I chose specifically to avoid the thermofilter models... I can deal with a Hydor malfunction by unplugging it and adding an internal heater to a tank. Very fast and easy and I could even not ever remove that inline heater despite not using it.

I'm not taking sides here, but I think TTA's answer addresses your last question. This is the same reason why I never liked combination all-in-one VCR-televisions or all-in-one (CPU/monitor) computers. If one part fails, the whole thing turns into a paperweight, or nearly so. If you have to return it to a store for servicing, you are at a loss for both functions, not just one. Moreso than pumps or lights, I find heaters to be... more often than not... the weak link in aquarium technology. If anything is going to burn out or fail, it's the heater before all else (not counting simple light bulbs). I have to agree that separate heating and cleaning systems seems wiser, even though I also agree with your (Gerald) other point:

Gerald CapeTown wrote:I do love good technology.

Cheers, Eric

Just to update... My solution to this is to replace the body section of the filters, either with new Thermofilter units or straight filter units, probably the latter as in my case I have spare heaters.