Problem with electrics at over 60mph

[pmannu]

Hi new to this forum but using it as a last resort. BOth my mechanic and I asr stumped on this one. In summary; main lights are on travelling and when I reach 60mph my abs and BAS lights alarm and infuriatingly keep goin of (also when the alarm goes off the main lights dim as if they are losing power).. When I reduce my speed to less than 40mph over a period of a minute the situation resolves itself. We have checked the voltage on the alternator and there doesn;t seem to be a drop in the voltage. Apart from changing the controller which is a hefty grand and may not work does anybody have an clues as to what is going wrong. Its just done 150,000 miles and a lot more life in her yet but this is a real problem.

Thanks for any help anyone can give me.

 

[television]

Cannot you just turn them off, are they in the running light mode

 

[Triv]

When the lights dim, does the steering stiffen up / get heavier?

 

[television]

OK you have edited the post since I replied, re the ABS it could be a wheel sensor fault, wrong tyres, a STAR check should reveal all.