Chaz
|
| posted on 19/7/06 at 08:21 PM |
|
|
Part-time Tacho
My tacho likes to read from 0-3000 and no more!!! When the needle reaches 3000 it stops...falls down...then it pops back up to 3000 when the engine
starts running down past 3000rpm and follows it down to zero again...WTF?
I have zetec with edis and smiths tacho...any ideas?
|
|
|
|
|
mark chandler
|
| posted on 19/7/06 at 08:45 PM |
|
|
Is the feed wire shielded ?
If not that may help, although only earth one end.
Rgds Mark
|
|
|
Chaz
|
| posted on 19/7/06 at 08:50 PM |
|
|
Its not like its twitching, it just seems to stop at the same place everytime??? Strange...
|
|
|
Bob C
|
| posted on 19/7/06 at 08:55 PM |
|
|
a million things could be the problem, but yours sounds like the tacho might benefit from a bigger signal - if you're feeding it from a
'logic' signal from ECU it might be 5V instead of 12, or not beefy enough. If you're taking the signal from the coil LT you might
have tapped off the ballast resistor side of the coil instead of the switchy side???
Point is I guess the smiths tacho is engineered to read coil LT type voltage, so the input is heavily filtered. SO when the frequency goes up, the
filtering makes the signal too small to detect.
Good luck - no doubt you'll find it's nothing to do with any of the above.......
Bob
|
|
|
MikeRJ
|
| posted on 19/7/06 at 09:42 PM |
|
|
Do you have diodes connected to the EDIS coil as per this thread ? (make sure you read the thread though!)
http://www.locostbuilders.co.uk/viewthread.php?tid=47440
|
|
|
Surrey Dave
|
| posted on 20/7/06 at 07:43 AM |
|
|
If you are using Megajolt , that is a common problem on older tacho's , you may have to connect to the coil leads with resistor / diode network
, that 's what I had to do with my old Skoda tacho.
|
|
|
Chaz
|
| posted on 20/7/06 at 09:28 AM |
|
|
OMG (baffled look)!! Sorry i'm not an electrician, that thread is v.difficult to follow MikeRJ.
The tacho i'm using is new. hmm. Thanks for your help guys i'll have to look into this alot closer.
|
|
|
MikeRJ
|
| posted on 21/7/06 at 10:22 AM |
|
|
You basicaly need two 1N4004s or better (e.g. 1N4005, 1N4006, 1N4007) and a zener diode of around 12-15volts. All parts available at Maplins or RS
Components or Farnell, or even Ebay.
 
Adapter to drive tachometer from wasted spark system (e.g. EDIS)
Actual layout of components, note the location of the stripes on the component bodies!
 
Layout of components
Hope that helps.
|
|
|
Surrey Dave
|
| posted on 21/7/06 at 05:57 PM |
|
|
That didn't work on mine I had to fit a resistor from the join of the diodes to earth , I think Paulf knows what value , 220 or 220k ohm rings a
bell.
|
|
|
paulf
|
| posted on 21/7/06 at 09:38 PM |
|
|
1K did the job on mine , anything that pulls it down to earth without drawing to large a current will do.
Paul.
quote:
Originally posted by Surrey Dave
That didn't work on mine I had to fit a resistor from the join of the diodes to earth , I think Paulf knows what value , 220 or 220k ohm rings a
bell.
|
|
|
Surrey Dave
|
| posted on 22/7/06 at 08:10 AM |
|
|
4.7k
The answer is here:
http://www.locostbuilders.co.uk/viewthread.php?tid=29956&page=1
|
|
|
Chaz
|
| posted on 23/7/06 at 10:18 AM |
|
|
Good work. Cheers
|
|
|
02GF74
|
| posted on 24/7/06 at 01:46 PM |
|
|
quote:
Originally posted by Chaz
Good work. Cheers
does that mean it now works?
|
|
|
.jpg)
