Background: I use reed with magnets under the cars to operate signals and switches. On my passenger route I have 10 reeds controlling the hidden yard and around 10 other reeds to operate signals and traffic control. For the steam, electric and diesel locs I use the 7558 magnet and for the ICE I use the 7556.

In testing the hidden yard there is one location where the reed does not activate the programmed action. But this only occurs for the ICE. . I have done the following in attempting to identify the issue and resolve.
- I pass a freight car over the reed and it activates the programmed routine - so the reed works
- I pass the ICE over the other reeds and each one activates - so the 7556 does activate reeds

This suggests the reed in question is 'weak'. So I replaced the reed (I have 2 spares) and the above still occurs. The 7558 activates the reed but the 7556 does not. This suggests the 7556 is of borderline strength

Next, I held a 7556 and passed it over the reed (literally brushing the reed). It activated the reed. This suggests the 7556 is not strong enough. I have placed 1, 2 and 3 7556's under the ICE (side by side) and still no success. Very puzzling and only thing I can think of is that a stronger magnet of same dimension (thickness) is needed. The dimension of the 7556 is 10x5x1.5 mm (the 1.5 is key.) In inches, 25/64x3/16x1/16

Does anyone know of a supplier who has this dimension and the magnet being stronger than the Marklin item. I don't know the strength of the Marklin item.

Thanks
Harvey

I take it that you already have studied the manual - but nevertheless:
https://static.maerklin....2df8923c341512382720.pdf

I too use magnets for activating the reed switches for my Rocrail block sensing. Unfortunately like you, I have found in most cases the Maerklin magnets are too weak if mounted as suggested and usually have to go to the next size up in order to get satisfactory functioning. However, in some cases especially near a curve they just do not function reliably.

In most cases I have switched to the Promag Neodymium magnets available from Michaels in North America. They come in 2 sizes and are very strong and in my experience if mounted properly are 99% reliable. Heed the warning if small kids are around. These can be deadly if swallowed by a small child.

Peter

I have ordered magnets and await arrival. In the meanwhile, will rub some magnets and see what happens

Thanks for the suggestions

Harvey