Tachometer woes!

Eeyore

Eeyore

Well-Known Member
Joined
5 Oct 2007
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Location
Kudat, Malaysia
www.yachtrhumbdo.co.uk
Has anyone else had problems changing to the new technology tachos? I have an old Mercedes OM636 with an equally old VDO tachometer which is driven by a VDO 4 pulse generator bolted on the rear of the injector pump. I bought new VDO viewline instruments, wired the tacho as instructed in the accompanying destruction sheet - and it doesn't work! I contacted the (now Swiss) owners, Veratron, who very nicely told me the unit was a piece of rubbish and they had withdrawn it from production. Pity the retailer didn't tell me that when I ordered it. Now I am having trouble sourcing a tachometer that will run off the pulse generator without going to the extortionate cost of replacing the generator with another type. Any suggestions chaps?
 
Eeyore said:
Has anyone else had problems changing to the new technology tachos? I have an old Mercedes OM636 with an equally old VDO tachometer which is driven by a VDO 4 pulse generator bolted on the rear of the injector pump. I bought new VDO viewline instruments, wired the tacho as instructed in the accompanying destruction sheet - and it doesn't work! I contacted the (now Swiss) owners, Veratron, who very nicely told me the unit was a piece of rubbish and they had withdrawn it from production. Pity the retailer didn't tell me that when I ordered it. Now I am having trouble sourcing a tachometer that will run off the pulse generator without going to the extortionate cost of replacing the generator with another type. Any suggestions chaps?
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One that runs from the "W" connection of the alternator?
 
Thanks, but there is no A/C take off point (terminal 'W') on my alternator and they are notoriously inaccurate, hence the need of one driven by the pulse generator. The Durite one looks good and might fit (depth wise) in my newly designed instrument fascia but it would mean finding an alternator shop capable of modifying the alternator, and that may not be possible here in Borneo.
 
Eeyore said:
Thanks, but there is no A/C take off point (terminal 'W') on my alternator and they are notoriously inaccurate, hence the need of one driven by the pulse generator. The Durite one looks good and might fit (depth wise) in my newly designed instrument fascia but it would mean finding an alternator shop capable of modifying the alternator, and that may not be possible here in Borneo.
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Do a google search "Adding W terminal to alternator" lots of info and not that difficult. Appreciate everyone not practically minded but deep breath and plenty of time should help.
 
Boater Sam said:
Could I ask why you need an accurate tach or one at all?
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I'd like one - just to be able to say ..... at xxxx rpm I have x knots !!

But being without one - I use sound and throttle lever position to set at a nice pleasant setting ....

;)

I have a hand held optical Tacho if I want to know RPM ... bit of reflective tape on crank pulley .... shine tacho on it ... read display.

I also have a 'bicycle' tacho ... that I thought to fix .. has the magnet on the 'wheel' - sensor fixed to frame ... I saw someone actually use one to feed pulses to a dial that he had created an RPM scale on ... but I would just have a chart converting the 'bicycle' display to RPM ...
 
Alex_Blackwood said:
Do a google search "Adding W terminal to alternator" lots of info and not that difficult. Appreciate everyone not practically minded but deep breath and plenty of time should help.
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Yes I'm aware of the info on youtube, google etc in respect of adding a 'w' terminal - I just have so many other jobs to do while sitting here at anchor and unable to go beyond a 10Km radius for the last 15 months! I might pull the alternator and have a go at it tomorrow. Still have to find and order another tacho as Veratron have rubbished their own product.
 
Eeyore said:
Yes I'm aware of the info on youtube, google etc in respect of adding a 'w' terminal - I just have so many other jobs to do while sitting here at anchor and unable to go beyond a 10Km radius for the last 15 months! I might pull the alternator and have a go at it tomorrow. Still have to find and order another tacho as Veratron have rubbished their own product.
Click to expand...
Good luck, hope you have success (y)
 
I am not sure if they are still produced, but TinyTach make a tacho which uses the impulses in the fuel injection system to drive a compact digital display. It also functions an hour meter and can show max and min rpm in the most recent engine run.
A small sensor is clamped to one of the injection pipes and that is wired to the display. Very easy to fit and use.
 
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