ABS sensor testing

[Eyvind Spangen]

How do I test the ABS sensors without the ABS-tester? I've measured
the resistance, they measure OK, but my ABS keeps switching off after
about 100 metres of driving, and before it switches off, the pump is
running. I've narrowed it down to sensors, tried reinstalling with new
caps, but no luck. I guess it's either dirty rotors or just bad
sensors. I'm thinking that an old-fashioned analog multimeter might
work, anybody BTDT?

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Regards,
ES
'90 200TQ, new winter tires, but non-functional ABS & diff lock..