CAT 3126 Electrical Control Box

Discussion in 'Diesel Engines/Drives/Transmissions/Props' started by dtfeld, Nov 16, 2019.

  1. dtfeld

    dtfeld Water Contrails GOLD Sponsor

    Jun 5, 2016
    Milton, GA
    410 Sundancer
    2001
    Axiom 12 MFD
    Cat 3126 V-Drives
    Going over the engines I found a loose/broken wire in the engine junction control box. I have the schematic, but can anybody explain the operation? Specifically the inlet air heaters?

    Are they temperature or time controlled?

    Is there a test proceedure for the heaters themselves? I think there are 3 connections, and either 2 or 3 wires as I recall.
     
  2. dtfeld

    dtfeld Water Contrails GOLD Sponsor

    Jun 5, 2016
    Milton, GA
    410 Sundancer
    2001
    Axiom 12 MFD
    Cat 3126 V-Drives
    Replacing this...
     

    Attached Files:

  3. dtfeld

    dtfeld Water Contrails GOLD Sponsor

    Jun 5, 2016
    Milton, GA
    410 Sundancer
    2001
    Axiom 12 MFD
    Cat 3126 V-Drives
    I have both air heater back in working order after repairing the broken ring terminal.

    Best of my understanding, these air heaters come on for 30 seconds when power applied and if the coolant temp is below 120F as a starting aid and to reduce white smoke on start up.

    They then alternate on/off for 30 seconds each. Seems about right, I can see them turning on/off on the voltage.
     
  4. carterchapman

    carterchapman Well-Known Member TECHNICAL Contributor SILVER Sponsor

    Mar 25, 2008
    Lake Chickamauga/Marietta, GA/Ft. Myers, FL
    2006 Sea Ray 58 DB
    MAN CRM V8-900s, Twin Disc Drives; Onan 21.5 Generator
    I recall that is correct. The Boat Diesel expert says you can disconnect them in the summer in the South.
     
    dtfeld likes this.
  5. dtfeld

    dtfeld Water Contrails GOLD Sponsor

    Jun 5, 2016
    Milton, GA
    410 Sundancer
    2001
    Axiom 12 MFD
    Cat 3126 V-Drives
    PO disconnected a couple wires and the one shown needed fixing. I put it back together and all is working as intended. With the winter temps around here, I need them working in the late fall/winter/early spring. I didn't notice a huge difference in the white smoke output, but maybe a slight improvement. Might help more in the summer on first fire up of the week-end. Once these motor are warm, no smoke issues.

    I could do like you Carter and add heater pads, but this keeps the energy bill down as its on demand only.
     
  6. JVM225

    JVM225 Well-Known Member GOLD Sponsor

    Apr 8, 2008
    Farmingdale, NY
    2002 410 Sundancer, Monaco Edition.
    3126 Cats.
    Dave,
    Not at the boat and can’t remember what it looks like in there, but is that wire connected to a relay in the electric box.
     
  7. carterchapman

    carterchapman Well-Known Member TECHNICAL Contributor SILVER Sponsor

    Mar 25, 2008
    Lake Chickamauga/Marietta, GA/Ft. Myers, FL
    2006 Sea Ray 58 DB
    MAN CRM V8-900s, Twin Disc Drives; Onan 21.5 Generator
    David,

    On my 410, I would turn the start switches on, let the heaters heat for 30 seconds, and then start the engines. Never did have any white smoke. If I didn’t wait to 30 seconds, my port engine is usually OK, but my starboard engine with white smoke - just a first puff.
     
  8. dtfeld

    dtfeld Water Contrails GOLD Sponsor

    Jun 5, 2016
    Milton, GA
    410 Sundancer
    2001
    Axiom 12 MFD
    Cat 3126 V-Drives
    The boat came from Florida, so PO disconnected the air heaters. Both of mine put out white smoke until warmed up. Worse in cold weather.

    I did read on boatdiesel.com to turn on and let heat for 30 seconds, so I’ll follow that procedure. Thanks Carter. Hopefully the white smoke issue lessens on start up (not too bad now). The good news is both engines fire off immediately.

    As far as operation, I believe the heaters should come on for 30 (or 10?) seconds before start. Then alternate on/off at 30 second intervals for 13 minutes or until Coolant temp reaches 120F. I’ve never come across a CAT official explanation.
     
  9. dtfeld

    dtfeld Water Contrails GOLD Sponsor

    Jun 5, 2016
    Milton, GA
    410 Sundancer
    2001
    Axiom 12 MFD
    Cat 3126 V-Drives
    I’d have to look at the schematic as well...I think the short wire goes between the 105A circuit breaker and one of the relays.
     
  10. JVM225

    JVM225 Well-Known Member GOLD Sponsor

    Apr 8, 2008
    Farmingdale, NY
    2002 410 Sundancer, Monaco Edition.
    3126 Cats.
    Thanks Dave.
    It’s on my “to do” list.
    at the end of last season I noticed an intermittent voltage drop on my starboard voltmeter.
    Sometimes I would start the motors and voltage would be at 12.5, other times I would start then and it would be at 13.5 or more.
    My thought was that the times when the voltage remained low might be due to a relay (if there is one) for the heater on that motor hanging up and leaving the heater on.
    If that’s the case, I’m going to have to identify and replace the relay if there is one.

    BTW: sounds like you are on the right track. The only time I get white smoke after starting is in the colder shoulder seasons.
     
    dtfeld likes this.
  11. carterchapman

    carterchapman Well-Known Member TECHNICAL Contributor SILVER Sponsor

    Mar 25, 2008
    Lake Chickamauga/Marietta, GA/Ft. Myers, FL
    2006 Sea Ray 58 DB
    MAN CRM V8-900s, Twin Disc Drives; Onan 21.5 Generator
    I wasn’t letting mine wait for 30 seconds at first. No smoke out of the port engine, one puff of white out the stbd. I asked my CAT expert at my CAT dealer in CHA and he laughed - he said “that’s the trouble with having two identical engines side by side - you expect them to be identical, but they usually are not!”.

    Interestingly, my MAN common rails do not have intake heaters or glow plugs, and they start instantaneously without any smoke of any kind..
     
    dtfeld and JVM225 like this.

Share This Page

Show Sidebar