ABS System on a 944/951

[arnebret]

Hi,

On my '88 951 there is something wrong with the ABS. At least, i thought there was... Normally, after a while the abs-light would come on and the abs would be disabled. This was going on for as long as i bought the car, the previous owner told me it were the sensors. When looking at the calipers i could clearly see two sensors missing at the rear, two sensors on the front, but not connected. It must be that, i thought. But as i asked around, people were saying these sensors never give any problem. So, might it have been other sensors i've been looking at between the brake pads??
Because, the strange thing is, the last two times i drove the car, the abs-light didn't come on and the brakes were working excellent (as normal) but the abs was doing his job as well. I found a bit of snow/ice on a piece of road and tried a hard brake... the abs worked and i came to a full stop without any problems in a very short time on ice. I was completly surprised that the abs worked so effectivly, but especially that it DID work at all. What could be wrong when abs starts working again after all the times it didn't... I have no idea about how the abs-system on the 951 works, so any info is welcome!!