Tach, Alternator odd trouble.... - SailNet Community

   Search Sailnet:

 forums  store  


Quick Menu
Forums           
Articles          
Galleries        
Boat Reviews  
Classifieds     
Search SailNet 
Boat Search (new)

Shop the
SailNet Store
Anchor Locker
Boatbuilding & Repair
Charts
Clothing
Electrical
Electronics
Engine
Hatches and Portlights
Interior And Galley
Maintenance
Marine Electronics
Navigation
Other Items
Plumbing and Pumps
Rigging
Safety
Sailing Hardware
Trailer & Watersports
Clearance Items

Advertise Here






Go Back   SailNet Community > On Board > Gear & Maintenance > Engines > Diesel
 Not a Member? 

Diesel This is a forum dedicated to diesel engines and their applicable accessories.


Like Tree1Likes
  • 1 Post By MarkSF
Reply
 
LinkBack Thread Tools
  #1  
Old 08-27-2013
Pacific Skipper
 
Join Date: Jan 2001
Location: Los Angeles / San Pedro / Palos Verdes
Posts: 27
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
Rasputin is on a distinguished road
Tach, Alternator odd trouble....

1986 Young Sun with an 80 HP Ford Lehman Diesel.

Earlier this winter, my alternator finally died. A new one has been installed along with a regulator. It´s been solid until a heater hose clamp failure that dripped coolant on it while it was running and hot. An alternator shop claims she´s still in good shape but: ISSUE: My tachometer now fluctuates and is off and on far more regularly. And when off, stays off for a while. (Usually first hour after starting engine.) ALSO, it does not charge batteries when the tach is at zero or fluctuating (I have checked batteries for input voltage and found no charge coming from alt).

Thoughts? Ideas on where to start? Possible issue(s)? I probably will call a mechanic but am looking to learn as much as possible to address myself when possible.

Thanks!
__________________

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Young Sun 50' Center Cockpit Cutter Sloop
Permanent Waves - Long Beach, CA. ~ USCG 673238
CBYC / LBYC
Reply With Quote Share with Facebook
  #2  
Old 08-27-2013
Faster's Avatar
Just another Moderator
 
Join Date: Sep 2005
Location: New Westminster, BC
Posts: 14,669
Thanks: 68
Thanked 192 Times in 184 Posts
Rep Power: 10
Faster has a spectacular aura about Faster has a spectacular aura about Faster has a spectacular aura about
Re: Tach, Alternator odd trouble....

Sounds like an alternator driven tach, and the symptoms look like worn brushes, or some other issue with the brush connections. Have you got a smart regulator, or is the tach driven direct from the internally regulated alternator?

The symptoms match failing brushes, but you'd think the alternator shop would have seen that...
dried antifreeze insulating the slip rings??
__________________
Ron

1984 Fast/Nicholson 345 "FastForward"

".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)
Reply With Quote Share with Facebook
  #3  
Old 08-27-2013
Senior Member
 
Join Date: Feb 2011
Location: San Francisco Bay area
Posts: 2,220
Thanks: 2
Thanked 36 Times in 36 Posts
Rep Power: 4
MarkSF is on a distinguished road
Re: Tach, Alternator odd trouble....

The tach signal comes from the alternator but there are things that could be wrong other than the alternator itself.

Some systems use 12V supplied via the ignition switch accessory position to provide the excite voltage. So a faulty ignition switch, or wiring between that and the alternator, could do the trick. Old ignition switches can develop bad contact, I replaced mine last year because it would only start the engine intermittently.

What do you mean "My tachometer now fluctuates and is off and on FAR MORE REGULARLY"? So it had this problem before you changed the alternator and it got worse? That really points to wiring.

Do you have an ignition light?
OPossumTX likes this.
__________________
1984 Bristol 31.1
Alameda, California, USA

Last edited by MarkSF; 08-27-2013 at 02:49 PM.
Reply With Quote Share with Facebook
  #4  
Old 08-28-2013
Pacific Skipper
 
Join Date: Jan 2001
Location: Los Angeles / San Pedro / Palos Verdes
Posts: 27
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
Rasputin is on a distinguished road
Re: Tach, Alternator odd trouble....

Thank you MarkSF and Faster.

I've had the boat 7 years this past July. On rare occasions in the past (maybe2 or 3 times a year at most), while motoring (again the motor RPM was consistent and running smooth) the tach would jump to zero, maybe stay there for a moment or two, jump back up to a higher RPM reading or maybe a lower reading or both but would quickly go back to normal after a few moments.

Since I put in the new alternator and had my hose clamp fail, the tach has done the same thing as above, but only for much longer periods (up to an hour). And I also finally noticed that when the tach was screwey, it also wasn't charging the house or engine batteries.

Yesterday - Wednesday Aug 27th. I replaced the original ignition button and key. I put in a brand new key switch (like a car). I'm positive all wires are tight and connected. If this doesn't fix it, I'll assume the shop missed the stuck brushes.

~Scott
__________________

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Young Sun 50' Center Cockpit Cutter Sloop
Permanent Waves - Long Beach, CA. ~ USCG 673238
CBYC / LBYC
Reply With Quote Share with Facebook
  #5  
Old 08-28-2013
Senior Member
 
Join Date: Jul 2007
Location: Truckee, CA
Posts: 7,504
Thanks: 2
Thanked 109 Times in 107 Posts
Rep Power: 8
dabnis is on a distinguished road
Re: Tach, Alternator odd trouble....

Quote:
Originally Posted by Rasputin View Post
Thank you MarkSF and Faster.

I've had the boat 7 years this past July. On rare occasions in the past (maybe2 or 3 times a year at most), while motoring (again the motor RPM was consistent and running smooth) the tach would jump to zero, maybe stay there for a moment or two, jump back up to a higher RPM reading or maybe a lower reading or both but would quickly go back to normal after a few moments.

Since I put in the new alternator and had my hose clamp fail, the tach has done the same thing as above, but only for much longer periods (up to an hour). And I also finally noticed that when the tach was screwey, it also wasn't charging the house or engine batteries.

Yesterday - Wednesday Aug 27th. I replaced the original ignition button and key. I put in a brand new key switch (like a car). I'm positive all wires are tight and connected. If this doesn't fix it, I'll assume the shop missed the stuck brushes.

~Scott
Where the tach was acting up before you changed the alternator, the wiring to the exciter terminal may be the cause?

If the new ignition switch doesn't solve the problem, you might try running a wire, through a switch, if you want, directly from the battery supply to the exciter terminal of the alternator? If that doesn't work then the contacts in the alternator may be the problem.

Paul T
Reply With Quote Share with Facebook
  #6  
Old 08-28-2013
Maine Sail's Avatar
Senior Member
 
Join Date: Jan 2003
Location: Maine Coast
Posts: 5,333
Thanks: 10
Thanked 120 Times in 88 Posts
Rep Power: 15
Maine Sail is just really nice Maine Sail is just really nice Maine Sail is just really nice Maine Sail is just really nice
Re: Tach, Alternator odd trouble....

Quote:
Originally Posted by Rasputin View Post
Thank you MarkSF and Faster.

I've had the boat 7 years this past July. On rare occasions in the past (maybe2 or 3 times a year at most), while motoring (again the motor RPM was consistent and running smooth) the tach would jump to zero, maybe stay there for a moment or two, jump back up to a higher RPM reading or maybe a lower reading or both but would quickly go back to normal after a few moments.
This can be normal behavior on an a alt with a sloppy regulator when the battery bank gets full. When the bank gets full if the regulator allows it to over-shoot its voltage limit, this can happen, it will cut the field power entirely thus shutting down the alt and tach. When the voltage drops it comes back on...

Quote:
Originally Posted by Rasputin View Post
Since I put in the new alternator and had my hose clamp fail, the tach has done the same thing as above, but only for much longer periods (up to an hour). And I also finally noticed that when the tach was screwey, it also wasn't charging the house or engine batteries.
This would not be normal unless you have an additional charging source such as solar, generator or wind on-board that have a higher regulation set point than the alternator regulator....
__________________
______
-Maine Sail / CS-36T


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.




© Images In Posts Property of Compass Marine Inc.


Reply With Quote Share with Facebook
  #7  
Old 08-29-2013
Pacific Skipper
 
Join Date: Jan 2001
Location: Los Angeles / San Pedro / Palos Verdes
Posts: 27
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
Rasputin is on a distinguished road
Re: Tach, Alternator odd trouble....

To Maine Sail: I would notice that the alternator wasn't charging after being on a mooring all weekend. The house batteries would be down to 12.2 or so and the starter battery would be at ~ 12.5/6. My point being, once the engine is on and we're motoring away from the mooring, the alternator shuold be doing some charging... and it isn't as long as the tach was going wacky.

I only have 3 sources of charge. Shore power, Alternator and a Honda 2000 Generator (which is terriffic). No wind or solar as of yet.

Huge thanks all. I'll be on the water this long weekend and see what transpires.
__________________

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Young Sun 50' Center Cockpit Cutter Sloop
Permanent Waves - Long Beach, CA. ~ USCG 673238
CBYC / LBYC
Reply With Quote Share with Facebook
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

 
Posting Rules
You may post new threads
You may post replies
You may post attachments
You may edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Tach PAULCR1 Gear & Maintenance 9 02-11-2013 11:01 AM
Replacing the Tach; Universal 5411 "Tiny Tach" jrhamp Diesel 3 10-23-2012 12:26 AM
Tach and alternator intermittent problem steveg353 Gear & Maintenance 2 04-20-2011 05:47 AM
I need a tach ekenna Electronics 0 03-09-2011 08:46 PM
desiel tach: Tiny-tach dreuge Diesel 5 04-30-2010 11:04 AM


All times are GMT -4. The time now is 12:40 AM.

Add to My Yahoo!         
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
(c) Marine.com LLC 2000-2012

The SailNet.com store is owned and operated by a company independent of the SailNet.com forum. You are now leaving the SailNet forum. Click OK to continue or Cancel to return to the SailNet forum.