Tach Filter question...
Thread Starter
Racer
Joined: Oct 2007
Posts: 270
Likes: 0
From: Chapel Hill NC
Tach Filter question...
My tach was acting unusual... working perfectly for a month, then just stops working totally for about a month... then coming back to life, etc.
So I just replaced the tach board, now the tach needle is jumpy, up and down in nervous pulses.... but the tach reads correctly.
If I bypass the filter, the tach works smoothly... but the readings are way off (too high).
What gives?
Where do you think my issue lies?
Is the tach filter required? (protecting from spikes)
So I just replaced the tach board, now the tach needle is jumpy, up and down in nervous pulses.... but the tach reads correctly.
If I bypass the filter, the tach works smoothly... but the readings are way off (too high).
What gives?
Where do you think my issue lies?
Is the tach filter required? (protecting from spikes)
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,114
From: Crossville TN
The tach filter IS required and is likely your problem, since you have repaired the board. The filter takes out any unwanted spikes from the tach signal (anything other than the signal pulses). Now that you have bypassed it, many 'false' tach pulses are affecting your tach reading. The fact that the reading is stable indicates that you fixed the board problem, but the filter is also bad. You can either buy one or make one (with a few dollar$ worth of Radio Shack parts). Search the CF Archives for info on that subject.
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,850
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
I’ve seen on original filters where the wires going in and out are broken and just sitting in the hole making random contact with the filter. This would cause you intermittent working tachometer and might be fixable if it’s an original filter.
Sometimes you can put a drop of solder in there and it will reconnect the wire. Food for thought and it might keep you from buying one.
Sometimes you can put a drop of solder in there and it will reconnect the wire. Food for thought and it might keep you from buying one.
Instructor
Joined: Aug 2005
Posts: 225
Likes: 0
mopkop
looking for the position of the tach filter do you have any photo's on that
regards
MOpkop
mopkop@netvigator.com
regards
MOpkop
mopkop@netvigator.com
