Low voltage from alternator on 12v92 DDEC

[northshoreone]

Ran the boat with the ZF transmission tech. on board yesterday to assure that my transmissions were operating properly and noticed that the port engine alternator actually dropped in voltage from like 12.6 volts to about 11.2 when rpm was increased! When you dropped it down in rpm to hull speed it returned to the 12.6 the starboard alternator seems to be working properly. Looking for direction for where to start looking for the issue and how to correct it.
Thanks

 

[JLR]

If the readout was taken from the ECM, check the Vanner that drops the output from 24V to 12V for the DDEC's. Also, on the analog battery gauge, verify that the alternator is putting out about 26 volts. Had the same issue. The Vanner was the problem.

 

[northshoreone]

Where would the Vanner be located?

 

[northshoreone]

And where did you get the replacement Vanner from?
Thanks

 

[JLR]

The Vanner is located between the batteries and the ECM for the DDEC. Is is a box with three terminals on it. One is for 24v one is for 12v and one for ground. They are pretty hefty cables, equal in size to battery cables. I bought mine from an outfit in NJ. I got the name of the distributor from Vanner. The exact replacement for the one you have is obsolete so you will need either a 65-60 or a 66-60. The distributor was not very knowledgeable on the units so I would verify the replacement model with Vanner. I paid $600 for mine after a bit of back and forth on the price. I am not certain that is the cause of your problem but it fixed my low voltage on the EDM after I verified it was not due to a bad alternator/regulator. If you can't get the number, I will get the phone number from my records on Monday.

 

[northshoreone]

I wasnt on the boat when I asked but then went there and saw it on the engine room wall. I will check the Alternator first and then go from there. Thanks for the fed back and I will get back with the results one way or the other.

 

[JLR]

Ruling out the alternator is a good first step. Remember though that anything below 12 volts on the EDM, would seem to indicate a Vanner issue.

 

[JLR]

Also, the Vanner website has a good description of how to test the Vanner.

 

[northshoreone]

Thanks again for the info, I will go to their site and check it out!

 

[JLR]

Keep us posted.

 

[northshoreone]

Alright...the Vanner is putting out 13 volts....alternator is putting out 27.9 volts..rated 28 volts and when running at about 1000 rpm the DDEC display shows 12.3 volts ( it shows 12.8 v prior to starting the engine ...the same as the other engine prior to start). Run it up on plane and its 11.4 volts. I shut down that engine and switched DDEC voltage source ..with the switch...so it now draws voltage from the Vanner on the other engine which is showing great voltage. I get the same voltage on the DDEC of 11.4 volts on plane...AHHHH So what am I still missing???