CAT 3126 Electrical Control Box

dtfeld

Water Contrails
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Jun 5, 2016
5,519
Milton, GA
Boat Info
410 Sundancer
2001
12" Axiom and 9" Axiom+ MFD
Engines
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.
 
Replacing this...
 

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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.
 
I recall that is correct. The Boat Diesel expert says you can disconnect them in the summer in the South.

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.
 
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.

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.
 
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.
 
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.
 
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.

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.
 
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.

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.
 
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.
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..
 

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