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jsmiller Samba Member
Joined: June 09, 2011 Posts: 24 Location: South Australia
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Posted: Tue Feb 03, 2015 4:51 am Post subject: Aftermarket Tachometer |
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Ok I'm sure this has been covered on here but after searching I couldn't find an answer! I have a 1990 caravelle (vanagon) 2.1 digifant. I currently have an old crappy aftermarket tach installed and it works fine (never had a factory in dash tach, it has the clock). So, here's the issue, I bought another tach (better looking, bigger etc) and it basically doesn't work! The needle just bounces all around and it's unreadable. So I thought the tach was broken. But I've heard it could be due to the signal from the ecu or the coil doing this? And that this is a digifant only thing? I had and 84 vanagon (digijet) years ago with the very same tach I'm tiring to install and it worked great! So surely someone has the answer? If it is a signal issue then why does the crappy old tach thats hooked up now work but not this brand new one? |
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djkeev Samba Moderator
Joined: September 30, 2007 Posts: 32433 Location: Reading Pennsylvania
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jsmiller Samba Member
Joined: June 09, 2011 Posts: 24 Location: South Australia
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Posted: Tue Feb 03, 2015 5:09 am Post subject: |
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New tach is an Autogage 2300 (ATM-2300), old tach (one hooked up now) I haven't a clue? It doesn't even have a name on it! |
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djkeev Samba Moderator
Joined: September 30, 2007 Posts: 32433 Location: Reading Pennsylvania
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jsmiller Samba Member
Joined: June 09, 2011 Posts: 24 Location: South Australia
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Posted: Tue Feb 03, 2015 5:18 am Post subject: |
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I've wired it up correctly, and yes the switches are set to the 4cyl position. The needle goes crazy, not just the wrong rpm reading. |
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danfromsyr Samba Member
Joined: March 01, 2004 Posts: 15130 Location: Syracuse, NY
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Posted: Tue Feb 03, 2015 7:02 am Post subject: |
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quite possibly your 85+ ECU puts out a different Tach signal than the tach is expecting
old early tachs (VW and other) use a signal from the coil to trigger
new tachs use a signal from the ECU
you likely need a Tach adapter, MSD is likely your best availability in Australia
Link: https://www.google.com/webhp?sourceid=chrome-insta...ch+adapter _________________
Abscate wrote: |
These are the reasons we have words like “wanker” |
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MarkWard Samba Member
Joined: February 09, 2005 Posts: 17014 Location: Retired South Florida
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Posted: Tue Feb 03, 2015 9:19 am Post subject: |
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I guess we need to know where you are getting your rpm signal from the ECU or directly from the ignition coil. _________________ ☮️ |
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jsmiller Samba Member
Joined: June 09, 2011 Posts: 24 Location: South Australia
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Posted: Tue Feb 03, 2015 1:41 pm Post subject: |
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I'm getting the signal from the the tach wire that goes to the cluster (pin 14??). But I've also wired it directly to the negative side of the coil and same thing happens! |
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crazyvwvanman Samba Member
Joined: January 28, 2008 Posts: 9895 Location: Orbiting San Diego
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Posted: Tue Feb 03, 2015 2:20 pm Post subject: |
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The tach wire on the dash cluster 14 pin connector comes from the coil negative side anyway, which is also connected to the ECU since the ECU is what fires the coil. (on USA/CA vans the tach signal is on pin 9 of 14)
There is a known issue with the tach signal on Digifant 2.1 models. The tach made for that works but other tachs often don't. Even the tach from an earlier Digijet can act crazy if hooked to the Digifant. Likewise the factory tach for Digifant models is known to give problems when you are trying to use it with something other than a Digifant.
Mark
jsmiller wrote: |
I'm getting the signal from the the tach wire that goes to the cluster (pin 14??). But I've also wired it directly to the negative side of the coil and same thing happens! |
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jsmiller Samba Member
Joined: June 09, 2011 Posts: 24 Location: South Australia
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Posted: Tue Feb 03, 2015 3:01 pm Post subject: |
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Ok pin 9 then, the green wire, the one the current tach is hooked too.
crazyvwvanman wrote: |
There is a known issue with the tach signal on Digifant 2.1 models. |
Well I'm thinking this must be the issue, but is there a known fix, or aftermarket tach that can read the signal? While I'd love to put a factory in dash tach in there, I've already got holes drilled in the dash for the tach that's there now. Plus a $60 aftermarket tach is way cheaper than and easier to find than a factory one. |
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djkeev Samba Moderator
Joined: September 30, 2007 Posts: 32433 Location: Reading Pennsylvania
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jsmiller Samba Member
Joined: June 09, 2011 Posts: 24 Location: South Australia
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Posted: Tue Feb 03, 2015 6:31 pm Post subject: |
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Thanks for that info Dave, however I don't believe this is and installation issue and is likely related the type of signal from the negative side of the coil specific to Digifant? Most tachometers rely on a 'square' type signal (I.e. on/off pulse from the coil) of which I'm starting to think (based on my research thus far) the Digifant system does not produce for reasons still unclear?
I'm tring to determine:
1. It's the signal from my Digifant coil unreadable by my new tachometer, and if so is there a solution? Different aftermarket tach that will work or some type of signal filter that will fix the issue; or
2. Is my newly purchased (Autogage 2300 tachometer) just broken?
As mentioned previously it appears to be a signal issue, that others have potentially also experienced? If any of you vanagon gurus can clear this up for me that would be much appreciated. |
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wcdennis Samba Member
Joined: July 20, 2004 Posts: 954 Location: Winston-Salem NC
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Posted: Tue Feb 03, 2015 8:09 pm Post subject: |
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Is it not worth even trying the resistor fix? |
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jsmiller Samba Member
Joined: June 09, 2011 Posts: 24 Location: South Australia
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Posted: Tue Feb 03, 2015 8:26 pm Post subject: |
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There's a video on YouTube by a 'mercedesdieselguy' where he had a similar issue when putting a tach in his 91. He did the resistor thing and it was no help? Hey I'd try it no worries just looking for a bit more of a solid confirmation that a fix actually does exist? |
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jsmiller Samba Member
Joined: June 09, 2011 Posts: 24 Location: South Australia
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Posted: Wed Feb 04, 2015 3:14 pm Post subject: |
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Ok I've heard that putting a diode in line with the signal wire might work? And someone on another forum said they used an 'older' VDO brand tach on their 89 and it worked?
Come on guys, surely there's a answer to this? I thought this would be a no brainer on here? Maybe it's more complicated than I thought? |
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crazyvwvanman Samba Member
Joined: January 28, 2008 Posts: 9895 Location: Orbiting San Diego
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Posted: Wed Feb 04, 2015 3:23 pm Post subject: |
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Most of our vans here came with tachs, the vast majority have them starting with 1985. Until recently they were easily available second hand at a reasonable price for people who wanted to add one.
Mark
jsmiller wrote: |
Ok I've heard that putting a diode in line with the signal wire might work? And someone on another forum said they used an 'older' VDO brand tach on their 89 and it worked?
Come on guys, surely there's a answer to this? I thought this would be a no brainer on here? Maybe it's more complicated than I thought? |
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Merian Samba Member
Joined: January 04, 2014 Posts: 5212 Location: Orygun
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Posted: Wed Feb 04, 2015 3:29 pm Post subject: |
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cars & tachs differ in how they do the pulse counting - e.g Porsche changed their method in the early 1970s
if the resistor doesn't work you might put a scope on the Van's trigger wire and see what it looks like |
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jsmiller Samba Member
Joined: June 09, 2011 Posts: 24 Location: South Australia
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Posted: Thu Feb 05, 2015 2:02 am Post subject: |
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Well someone suggested putting a diode in line with wire from the coil. So I tried it when i got home from work. It was worth a try I guess. But it didnt work, same issue diode or not?
How can the signal from the negative side of the coil have such a erratic pattern to we're a standard tachometer won't read it and the car still run? I'm starting to get pretty frustrated here. Especially because in sure it's a very simple answer!
Anywoo back to square one. |
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djkeev Samba Moderator
Joined: September 30, 2007 Posts: 32433 Location: Reading Pennsylvania
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Gauche1968 Samba Member
Joined: April 13, 2006 Posts: 1518
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Posted: Thu Feb 05, 2015 8:40 am Post subject: |
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crazyvwvanman wrote: |
The tach wire on the dash cluster 14 pin connector comes from the coil negative side anyway, which is also connected to the ECU since the ECU is what fires the coil. (on USA/CA vans the tach signal is on pin 9 of 14)
There is a known issue with the tach signal on Digifant 2.1 models. The tach made for that works but other tachs often don't. Even the tach from an earlier Digijet can act crazy if hooked to the Digifant. Likewise the factory tach for Digifant models is known to give problems when you are trying to use it with something other than a Digifant.
Mark
jsmiller wrote: |
I'm getting the signal from the the tach wire that goes to the cluster (pin 14??). But I've also wired it directly to the negative side of the coil and same thing happens! |
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Using two Digifant tachs on Digijet without any problems.... _________________ 1984 Vanagon GL
1984 Vanagon Westy |
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