Cruisers Forum
 


Join CruisersForum Today

Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on Cruisers Forums. Advertise Here
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 12-10-2018, 02:11   #1
Senior Cruiser
 
OldManMirage's Avatar

Cruisers Forum Supporter

Join Date: May 2017
Location: NE Florida
Boat: Cape Dory 28
Posts: 208
Tach Send for Tachometer 4 wire VS. 3 wire

I have a question here I hope someone can answer for me.

My Volvo MD7A has a tach send that comes off the camshaft I believe. It is two wires. The tach doesn't seem to care which is which, it is a 4 wire tach that uses the "W" and "G" for the send.

I'm looking at a new panel upgrade that has a 3 wire tach. I believe I can just connect the "G" wire to the negative ? The "W" would go to the "Tach Send."

And thoughts on this ?
__________________

__________________
Old Man and Miss Mirage
YouTube Channel - https://www.youtube.com/channel/UCb6..._as=subscriber
OldManMirage is offline   Reply With Quote
Old 14-10-2018, 02:17   #2
Senior Cruiser
 
OldManMirage's Avatar

Cruisers Forum Supporter

Join Date: May 2017
Location: NE Florida
Boat: Cape Dory 28
Posts: 208
Re: Tach Send for Tachometer 4 wire VS. 3 wire

The silence is awkward.
__________________

__________________
Old Man and Miss Mirage
YouTube Channel - https://www.youtube.com/channel/UCb6..._as=subscriber
OldManMirage is offline   Reply With Quote
Old 14-10-2018, 11:29   #3
Senior Cruiser
 
OldManMirage's Avatar

Cruisers Forum Supporter

Join Date: May 2017
Location: NE Florida
Boat: Cape Dory 28
Posts: 208
Re: Tach Send for Tachometer 4 wire VS. 3 wire

Am I not asking the right question ? Or is my explanation poor ?

I guess I can go trial and error but I thought some pretty good mechanics were on here and would have come across this before.
__________________
Old Man and Miss Mirage
YouTube Channel - https://www.youtube.com/channel/UCb6..._as=subscriber
OldManMirage is offline   Reply With Quote
Old 14-10-2018, 19:18   #4
Certifiable Refitter/Senior Wannbe
 
Wotname's Avatar

Cruisers Forum Supporter

Join Date: Jan 2008
Location: South of 43 S, Australia
Boat: C.L.O.D.
Posts: 8,541
Re: Tach Send for Tachometer 4 wire VS. 3 wire

I don't have direct knowledge of the Volvo MD7A tach circuit but I do know a little bit about some electrical/electronic systems.

From your description it would seem the old Volvo circuit had a two terminal tach sender on the engine (neither of which is connected to the frame of the sender) and these was connected to two terminals on the tach meter and the polarity of these two wires didn't matter.

Also the new tach meter only has three wires which presumably are 12v power positive, 12V negative and the tach sender wire.

If both of the above assumptions are correct, I would approach the wiring this way.
Connect the tach meter power wires (+ve and -ve) in the normal manner and then connect the tach meter sender wire from the tach meter to either of the terminals on the engine sender and the other one on the sender to engine ground (i.e. 12V -ve). If that doesn't work , reverse the wires on the terminals of the engine sender. If still no joy, perhaps the new tach isn't compatible with the Volvo engine sender.

What is the make / model of the new tach meter?
__________________
All men dream: but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find it was vanity: but the dreamers of the day are dangereous men, for they may act their dreams with open eyes, to make it possible. T.E. Lawrence
Wotname is online now   Reply With Quote
Old 15-10-2018, 10:13   #5
Senior Cruiser
 
OldManMirage's Avatar

Cruisers Forum Supporter

Join Date: May 2017
Location: NE Florida
Boat: Cape Dory 28
Posts: 208
Re: Tach Send for Tachometer 4 wire VS. 3 wire

Thanks for the reply Wotname, that's pretty much what my thinking was.

I don't know the brand of the new tach, I haven't bought the panel yet. There is a company in California (I think) called ACDCMarine that builds them.

You understood exactly what I was trying to say. Thanks again. I suppose the smart thing to do would be to email them also.

__________________
Old Man and Miss Mirage
YouTube Channel - https://www.youtube.com/channel/UCb6..._as=subscriber
OldManMirage is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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
Using "Send to GPS" to send via IP? jim326 OpenCPN 10 30-03-2016 17:41
Yanmar 2GM20F tach Glenn Whaley Engines and Propulsion Systems 4 12-07-2008 03:47
Yanmar intermitant tach and instruments Celestialsailor Engines and Propulsion Systems 6 24-07-2007 19:50
Tach slow/alternator not producing starfish62 Engines and Propulsion Systems 15 28-05-2007 15:04
Anyone know about debugging a flaky tach? Paul L Engines and Propulsion Systems 2 31-07-2005 05:15



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 15:18.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2018, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.