Post by Deleted on Jul 30, 2020 12:02:16 GMT
For awhile know my rev counter has been very erratic- over reading, under reading, wombling free sort of thing. Outwardly everything checked out ok, no loose connections, good belt tension, charging well, good voltage etc.
I havenβt stressed about it too much as these days the boost gauge is of more interest than the tach ππ
On our run to the Kings Head the alternator have a couple of bearing type squeals - still charging well but was enough of a warning to prompt me to do something about it before we set off in August.
Yesterday off came the alternator replaced with my spare I keep onboard - straight onto the operating table first thing this morning.
Ran the engine up, tach back to normal service π
The alternator is a Lucas A127 of 1989 vintage, I had replaced the regulator a couple of years ago to get from 13.7v to 14.4v, this was done insitu, the old brushes didnβt look bad, worn but nice and flat so I wasnβt unduly worried about the slip rings.
On stripping down the unit the first thing that was noticeable was the wear on the brushes, the rear most having worn with a pronounced shoulder on both edges, thatβs intriguing....
Sure enough, once I had it all to bits one slip ring had a deep groove worn into it, this is the most likely cause of the erratic tach operation, brush bouncing around but still making contact with the slip ring well enough to generate a decent amount of juice.
Bearings were fine, as was the rectifier, all diodes checked out ok.
Β£23 lighter and a nice man from Mid Ulster Rotating Electrics is winging a rebuild kit my way. Made more sense to leave Β£23 in a box in the locker rather than Β£60 plus for a Chinese unit Of unknown provenance.
Iβll stick some pictures up when it all goes back together next week.
TL;DR if your tach is shite itβs most likely worn brushes and slip rings π
I havenβt stressed about it too much as these days the boost gauge is of more interest than the tach ππ
On our run to the Kings Head the alternator have a couple of bearing type squeals - still charging well but was enough of a warning to prompt me to do something about it before we set off in August.
Yesterday off came the alternator replaced with my spare I keep onboard - straight onto the operating table first thing this morning.
Ran the engine up, tach back to normal service π
The alternator is a Lucas A127 of 1989 vintage, I had replaced the regulator a couple of years ago to get from 13.7v to 14.4v, this was done insitu, the old brushes didnβt look bad, worn but nice and flat so I wasnβt unduly worried about the slip rings.
On stripping down the unit the first thing that was noticeable was the wear on the brushes, the rear most having worn with a pronounced shoulder on both edges, thatβs intriguing....
Sure enough, once I had it all to bits one slip ring had a deep groove worn into it, this is the most likely cause of the erratic tach operation, brush bouncing around but still making contact with the slip ring well enough to generate a decent amount of juice.
Bearings were fine, as was the rectifier, all diodes checked out ok.
Β£23 lighter and a nice man from Mid Ulster Rotating Electrics is winging a rebuild kit my way. Made more sense to leave Β£23 in a box in the locker rather than Β£60 plus for a Chinese unit Of unknown provenance.
Iβll stick some pictures up when it all goes back together next week.
TL;DR if your tach is shite itβs most likely worn brushes and slip rings π