"Bounding" Tachometer on Perkins 5154

[montenido]

Hi all,

I have an intermittent problem with my tach. My alternator is set to not charge immediately, giving the engine 5 minutes or so to warm up first. So the tach reads zero for those 5 minutes. Once the alternator kicks in the tach reads normally. Occasionally, like now, the tach will bounce from zero to the actual RPM, stay there for a few seconds, then drop to zero before bouncing back up.

Connections at the rear of the tach are all clean and tight. the connections coming out of the alternator appear sound as well. What do I check next?

Thanks, Bill

[atoll]

is the fan belt slipping when the alternater kicks in ,check your belt tension

[montenido]

No, the belt is not slipping. This condition pops up after hours of motoring generally.


Bill

[Stu Jackson]

Could be the bank is fully charged and the regulator is just cutting off.

[svHyLyte]

Originally Posted by montenido

Hi all,

I have an intermittent problem with my tach. My alternator is set to not charge immediately, giving the engine 5 minutes or so to warm up first. So the tach reads zero for those 5 minutes. Once the alternator kicks in the tach reads normally. Occasionally, like now, the tach will bounce from zero to the actual RPM, stay there for a few seconds, then drop to zero before bouncing back up.

Connections at the rear of the tach are all clean and tight. the connections coming out of the alternator appear sound as well. What do I check next?

Thanks, Bill

Batteries are likely at full charge. Add a load--lights, fan, refer, what have you and it will likely stabilize. It's not an uncommon occurance.

[transmitterdan]

Other posters nailed the problem. Turn on a large incandescent lamp and if tach runs all the time that proves the theory.

Some external regulators have a fix for this well known issue.