Unusually high alternator output Cat 3116

peterkvs

peterkvs

Active Member
Nov 11, 2012
511
Guntersville, Alabama
Boat Info
400 Sundancer 1999
Engines
3116 Cats, 1000 hours
I was on the end of a 100 mile trip yesterday and noticed the voltage varying on my port xantrex battery monitor about a half volt. I switched the monitor to current mode and it was charging at 20 amps, but the current draw would rapidly vary from 18 to 30 amps. I turned off all electronics and the values did not change. I shut the engine off and the charging went away. As soon as I started the engine it went back to this behavior. So either the batteries or the alternator must be causing this erratic charging behavior. Also I should note that the generator was running with the ac converter on for hours prior to this so the batteries should not need any charging at all. The behavior continued need after I turned off the ac converter. Any thoughts?

Pete
 
Bad voltage regulator in the alternator?

I recently had to replace both of my alternators and found Caterpillar’s OEM supplier and bought replacements directly from them for about $260 ea. or less than 1/2 the price at the Cat dealer. I’ll look up the vendor and part no. if you need them.
 
Be sure you are buying new Leece-Neville not a rebuilt alternator with Chineese components. Wh ois the vendor and are they a L-N/Prestolite dealer? $195 seems too cheap.
 
Received the alternators today, Came in a nice Prestolite, Leece - Neville box. They look really good, Black, Nothing some Cat white paint won't take care of. Be a few weeks before I get them on. Update then.
 
Be aware that the new alternators do not turn on until you run the RPM's uo tp abput 1000 rpm. If you crank them at the dock and run the engine at normal idle speed, the voltage is going to look low. Run the rpm's up a bit momentarily, then back to idle and you will see the voltage jump up to 13.6-13.8V.
 
fwebster said:
Be aware that the new alternators do not turn on until you run the RPM's uo tp abput 1000 rpm. If you crank them at the dock and run the engine at normal idle speed, the voltage is going to look low. Run the rpm's up a bit momentarily, then back to idle and you will see the voltage jump up to 13.6-13.8V.
Click to expand...
Frank is this evertime you start the engines or just the first time after you install the new altenators? I have a 2001 and both altenators take a few minutes before the voltmeters register that they are charging the batteries. I have not tried bumping up the rpm'sover 1k to see if that works.
 
Pete - I had these exact units on the 400DA. It's unusual but if you get no output when increasing the engine's RPM that most likely means they have been sitting in the boxes for a long time and lost the residual magnetism and will need to be "excited". Simple procedure -
Also on these units the output voltage is adjustable through the little potentiometer on the back of the housing; I set mine to 14.3 volts at 1200 engine RPM using a digital meter on the alternator's B+ post.
 
Nevr Say Nevr said:
Frank is this evertime you start the engines or just the first time after you install the new altenators? I have a 2001 and both altenators take a few minutes before the voltmeters register that they are charging the batteries. I have not tried bumping up the rpm'sover 1k to see if that works.
Click to expand...


Yes.

Here is the Leece - Neville spec sheet for tat alternator. See the notes section at the top. The cut-in speed is 1500 rpm. This is the alternator rpm, not the engine rpm. Mine cut in at about 1000-1200 engine rpm.

http://www.prestolite.com/pgs_products/specs.php?item_detail_id=897&item=8MR2070TA
 
You must log in or register to reply here.

Forum statistics

Threads
113,163
Messages
1,427,620
Members
61,073
Latest member
kolak3
Back
Top