Suppressing electrical noise from alternator??

[srp]

Bought a Tiny Tach earlier this year, which started to play up, and was very speedily replaced by the UK distributor. The second one has also gone a bit strange on me and is in the process of being (very speedily again) replaced. The suggestion is that interference from the alternator is the cause of the problem, so I'm wondering if it is possible to suppress it in some way. The engine is a new 1gm10.
BTW, if anyone is thinking of buying a Tiny Tach, don't be put off by this - the support is absolutely first class and I'm sure mine is an isolated problem.

 

[2Tizwoz]

The usual method for supressing an alternator is with a small capacitor connecting the output to earth. If you have an AM radio connected you may be able to hear interference being produced whilst the alternator is running if this is the source of the problem.