Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 31-07-2009, 01:27   #1
Registered User

Join Date: Jul 2009
Posts: 3
Yanmar 3ym20 VDO Tachometer Settings

Hi,

I have a Yanmar 3ym20 motor in my Beneteau First 31.7. The tachometer went crazy, showing first full RPM and after the next start zero RPMs. Also digital hour meter started blinking.

The tachometer is a VDO made unit, in a Yanmar B Panel.

I first thought it must be a wiring issue, or alternator issue but then proved both assumptions were wrong. Finally I tried to change tachometer settings and that solved the problem: now I get some near correct readings out of the tachometer and hour meter also works.

Now the problem is how to figure out correct pulses/round settings without any meter to show the RPM?
Does anyone know how many pulses per revolution the standard Yanmar alternator produces?
Or even better, what is the correct setting for this yanmar tachometer?

I don't have a clue how the tachometer lost its settings. Does anyone have similar problems?

BR,

--Jussi
__________________

__________________
jussip is offline   Reply With Quote
Old 31-07-2009, 06:03   #2
Registered User
 
Sunspot Baby's Avatar

Join Date: May 2003
Location: New Bern, NC
Boat: Prout Manta 38' Catamaran - Sunspot Baby
Posts: 1,521
Images: 14
You can use a strobe to determine true RPM and then adjust the tach to match.

George
__________________

__________________
She took my address and my name
Put my credit to shame
Sunspot Baby, sure had a real good time
Bob Seger
Sunspot Baby is offline   Reply With Quote
Old 31-07-2009, 06:51   #3
Moderator Emeritus
 
GordMay's Avatar

Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 31,595
Images: 240
See “Calibrating the Tachometer”

http://usa.vdo.com/NR/rdonlyres/09F0...eHourMeter.pdf
or
http://www.egauges.com/pdf/vdo/0-515-012-037.pdf

If you have additional questions contact VDO:
Repair & Service for OEM Instrument Clusters and Systems
Merri MCIntyre
Phone: 540-665-2446
Fax: 540-662-2515
Email: mmcintyre@vdo.com
__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"



GordMay is online now   Reply With Quote
Old 31-07-2009, 07:39   #4
Registered User

Join Date: Jul 2009
Posts: 3
Thanks for the documents, however I already found them earlier.

I don't have a strobe or anything else to measure the real RPM.

I'd just neet to know how many pulses per revolution the alternator produces, I'd then be able to calculate correct pulses/revolution factor for the tachometer using following formula:

pulses/motor rev = alternator pulses/rev * alternator gearing

This is not a real big issue, I already have it close because I know the idle speed was somewhere near 800 and I have set the tacho for that...

BR,

--Jussi
__________________
jussip is offline   Reply With Quote
Old 31-07-2009, 09:16   #5
Moderator Emeritus
 
GordMay's Avatar

Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 31,595
Images: 240
Hitachi alternators typically have 8 or 12 poles.
You can count them by removing the pulley & fan. You could ask a Yanmar dealer.

Pulses per Revolution = (NUMBER OF POLES ÷ 2) x PULLEY RATIO

The standard alternator for a 3YM20 is a 60A or optional 80A Hitachi.
__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"



GordMay is online now   Reply With Quote
Reply

Tags
yanmar

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Where is the Tachometer sensor on a Yanmar 4JH3e? MarkJ Engines and Propulsion Systems 9 31-01-2009 18:41
VDO Ocean Line in UK collordon Marine Electronics 0 20-09-2008 11:03
Yanmar with funny Tachometer 45Sticks Engines and Propulsion Systems 1 14-07-2008 19:41
Continental acquires VDO GordMay Electrical: Batteries, Generators & Solar 0 06-12-2007 04:03
Default notification email settings... coot Forum Tech Support & Site Help 1 02-04-2006 22:15



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 06:01.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.