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 24-08-2019, 12:24   #1
Registered User
 
Peregrine1983's Avatar

Join Date: Aug 2016
Posts: 803
Bizarre voltage drop

Curious if anyone can shed some light on this issue...

We recently replaced our Raymarine autopilot computer because the old one was fried.

This morning while underway under sail we had the autopilot steering for about 5 hours in about 20kts of wind. I then noticed that our Vesper XB8000 AIS wasn’t transmitting or receiving.

I went below, checked connections, looked OK. Breaker not tripped. Volt meter on panel showing around 12.3v in the batt bank. I ended up pulling the power wires from the ais unit and testing with a voltmeter - the voltage was fluctuating from 12.x down to 2-3 volts every couple of seconds. It seemed to correspond with the autopilot drive unit engaging. Time to shut off the autopilot.

Thinking this meant the autopilot had basically drained our house battery bank (600ah golf cart batts), I had my wife hand steer and turned on the engine to charge them up. I figured our 300w of solar would not be enough to charge them up in any reasonable amount of time if they were so low that the autopilot drive was causing such a huge voltage drop.

With the autopilot off and the engine on the power wires to the AIS now say about 13.8x. I reconnect them to the ais, but the unit won’t power on. When I stick the voltmeter probes into the butt connector connecting the ais unit to the power wires it shows that same low voltage of 2-3v, but now constant at just 2-3v.

I remove the butt connectors and disconnect the ais, check the power wires again coming direct from the panel and they read 13.8x. Reconnect to the ais, the ais wont turn on and the same wires show 2-3 volts.

I’m super confused. Any ideas what is happening here? Now I’m concerned that some sort of power issue fried our old autopilot and is on track to fry other gear.
__________________

Peregrine1983 is offline   Reply With Quote
Old 24-08-2019, 13:00   #2
Registered User

Join Date: Jan 2008
Location: SF Bay Area (Boat in La Paz)
Boat: Valiant V40
Posts: 717
Re: Bizarre voltage drop

I would suspect a bad connection at the other end of the power cable. Don't forget to check both positive and negative leads, could be on the ground side.
__________________

jamhass is offline   Reply With Quote
Old 24-08-2019, 13:08   #3
Registered User
 
Peregrine1983's Avatar

Join Date: Aug 2016
Posts: 803
Re: Bizarre voltage drop

Thanks jamhass. Will check that and report back.
Peregrine1983 is offline   Reply With Quote
Old 24-08-2019, 13:12   #4
Registered User
 
DeepFrz's Avatar

Cruisers Forum Supporter

Join Date: Mar 2006
Location: Winnipeg
Boat: None at this time
Posts: 8,461
Re: Bizarre voltage drop

Sounds like you have a bad connection or wire to the AIS. Also maybe your batteries are weak. Just guessing because you haven't given us much to go on like battery age, usage, charging regime, etc.
DeepFrz is offline   Reply With Quote
Old 24-08-2019, 13:22   #5
Registered User
 
Peregrine1983's Avatar

Join Date: Aug 2016
Posts: 803
Re: Bizarre voltage drop

Quote:
Originally Posted by DeepFrz View Post
Sounds like you have a bad connection or wire to the AIS. Also maybe your batteries are weak. Just guessing because you haven't given us much to go on like battery age, usage, charging regime, etc.
Thank you. I do not think the batts are weak. Performance has been fantastic. Topped them all off with distilled water just a few weeks ago. They are 4xDuracell 6v golf cart batteries in two 12v pairs. 2017 vintage. Charging is through 300w of solar into a Victron 15/75 charge controller and from the motor through a 150 amp alternator through a Aqualine Plus marine regulator. Batteries have seen heavy use over the past 4 weeks due to a long cruise, but I'm inclined now to think this may be a negative/ground connection issue. I need to wait until we stop to take the panel apart, but will report back.
Peregrine1983 is offline   Reply With Quote
Old 31-08-2019, 13:54   #6
Registered User

Join Date: Aug 2015
Posts: 461
Re: Bizarre voltage drop

You have a bad connection somewhere in the wiring. When the AIS is not operating there is no current draw so no voltage drop. Diagnosis is simple... make sure current us flowing in the power wires and use you meter to check the voltage at each end and at any splices that exist in the wiring.
boatbod is offline   Reply With Quote
Old 31-08-2019, 15:39   #7
Registered User

Join Date: Aug 2009
Location: between the devil and the deep blue sea
Boat: a sailing boat
Posts: 18,546
Re: Bizarre voltage drop

To me sounds like something shorted on the ais unit pcb.


If I read you post right.


b.
barnakiel is online now   Reply With Quote
Old 09-09-2019, 07:25   #8
Registered User
 
Peregrine1983's Avatar

Join Date: Aug 2016
Posts: 803
Re: Bizarre voltage drop

Promised I would report back on this fwiw... turned out to be a bad breaker. The terminals on the back were loose and every other rock back and forth of the boat was causing the voltage to drop on the positive. I’ll likely be replacing my breaker panel this winter as it’s the original Marinetics.
__________________

Peregrine1983 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
Bizarre Weather Phenomenon Dockhead Weather | Gear, Reports and Resources 33 27-05-2014 13:51
Bizarre Nuts Target9000 Construction, Maintenance & Refit 3 30-12-2012 14:50
Bizarre FrigoBoat Behaviour ! s/v Jedi Plumbing Systems and Fixtures 35 26-10-2012 17:50
Bizarre Sounds In the Night ahnutts! Off Topic Forum 3 29-08-2011 06:28
Bizarre calcification issue on props and shafts aquabumdotnet Propellers & Drive Systems 9 18-07-2008 08:12

Advertise Here


All times are GMT -7. The time now is 13:17.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2020, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.