ECM control for air heaters

[Kevin Carlson]

I am having trouble with my air heaters on my 1998 Cummins 270 serial number 45661773. I know you recommend removing them but I am stubborn and want to know how they work. My port engine heaters worked fine, I could hear a click when turning on the key, the wait to start light illuminated and they started easy. The starboard solenoids didn’t work and the wait to start light didn’t light up. So to diagnose the problem I hooked up a test light to one of the small wire terminals on the magnetic switch on the port engine (since it is easier to reach the port engine switches.) and turned on the key. No power indicated and my wait to start light did not light up. So now neither engine has a working air heater. I removed one of the magnetic switch on the port engine and tested it and it works fine.
What I want to know is what exactly energizes the magnetic switches. I assume the ECM does this but I have no clue where it is or how to test it.
I attached a couple of pictures in hopes that it helps identify what I am working on.

Topic

[Kevin Carlson]

Well after spending hours running a power line to the fuse on the engine from the ignition switch, everything worked fine; once!
Now it never works. I thought maybe I have to ground the other side of the fuse, so I ran a wire to ground, no difference.
Does this mean the ECM on both engines suddenly doesn’t work? How much is a new ECM?

Kevin

[Kevin Carlson]

Thanks Tom that is exactly how I plan to use it, but it is nice to know that if you forget to turn it off the system will still act normally. I was worried that the air heaters would be on all the time the switch was on.
Kevin

[firehoser75]

Hi Kevin,
The purpose of the switch I wired in was to be in total control of the air preheat (only). With the switch “on” the air preheat will function as designed by Cummins, in other words it will preheat prior to engine start, then cycle on and off until you either reach the preset temp or RPM. With the switch “off” the preheat will not come on at all, but all else will function normally!
I like to turn my preheat off as soon as the engine starts, especially if I will be using the thruster or windlass, as the preheat really taxes the alternator! The switch allows total control, but you must get into the correct habits. “Prior to start check switch is on, as soon as start switch goes off”.
Hope that helps,
Tom

[Kevin Carlson]

Well for those out there that are as dense as me, the correct way to activate the ECM circuit as shown in the article is to apply power to one side of the fuse terminal as I described above.
I did like Firehoser75 said and took the power off of the ignition switch to a 3 amp fuse and then to the on/off switch.
And to answer my second question, after doing this the ECM controls all functions normally. It cycles on and off every 5 seconds and cuts out at 950 RPMs.

Kevin

[Kevin Carlson]

Ok I am going to need some serious hand holding. The article say to put a switch between the 2 wires designated, so when the switch is closed it would be the same as if the fuse were in place.
So I guessed that I would have to apply power to one of the wires. I tested both side of the fuse holder and found one went to ground and the other one didn’t. So I applied power to that one and the solenoid clicked.
So my question is do I only have to get power to one side of the fuse holder and everything will work.

Second question is: If this works will the ECM still control everything so that the it will cycle the heat and shut down at the correct temp and RPM?

Kevin

[Rob Schepis]

firehoser75 wrote:

Kevin,

This is the article I used to set up my “pre-heat” control switch. I also have a Wolverine oil pan heater.

https://www.sbmar.com/articles/electrical-instrumentation/dealing-with-the-cummins-marine-air-heater-circuit/

That is correct and that is why I circled those bundled connectors.

[firehoser75]

Kevin,
This is the article I used to set up my “pre-heat” control switch. I also have a Wolverine oil pan heater.

How to Deal with the Cummins Marine Air Heater Circuit

[firehoser75]

Hi Kevin,
That article (and engine setup) does not look familiar. The changes I made were on the injector pump side of the engine to some “low amperage” wiring and fuse holder. We added a “on / off ” switch at the helm, and connected into the starting key switch wiring so that the switch only functions when the key is on.
I found the “how to” on this site! The whole job only took about 1 hour.
The actual “magnetic switches” are on the other side of the engine on my 2002 6BTA.

[Kevin Carlson]

Firehoser7 5,
did you use the existing magnetic switches (solenoids) and heavy wiring or set it up like in Tony’s tips?

Simple Cummins Marine Grid Pre-Heater Control Setup

With 2 heating elements per engine and 2 engines this seems like a daunting task without using the existing solenoids.
Kevin

[Rob Schepis]

Kevin Carlson wrote:

It appears the only thing I can check is the 10 amp fuse that goes to the ECM. Would this red button be that fuse?

No, that’s the circuit breaker for the engine harness back to the helm. Plenty here on that: https://www.sbmar.com/community/search/engine+mounted+circuit+breaker/?gdpos=power-search-request&gdpos_search_users_input=rob

See attached pic – air heater control fuse should be in here

[Corey Schmidt]

Kevin Carlson wrote:

It appears the only thing I can check is the 10 amp fuse that goes to the ECM. Would this red button be that fuse?

If the engine still starts and runs, then the fuse is GOOD.

[firehoser75]

Check out Tony’s tips on the air preheater. I installed a “cut off” switch so now, my air heaters only come on when I want them to. So, I turn on the preheat prior to the engine start, then as soon as it starts, I shut them off. This does not work the alternator as hard prior to the engine getting totally up to temp. Tony has an article on how to do this complete with photos.

[Kevin Carlson]

It appears the only thing I can check is the 10 amp fuse that goes to the ECM. Would this red button be that fuse?

[Corey Schmidt]

The ECM is supposed to control everything as it assesses sensor input, etc.

When you figure out how it all works, can you let us know? LOL

Here’s a link to the Cummins diagram: https://www.sbmar.com/articles/electrical-instrumentation/cummins-marine-heater-grid-assembly-wiring-diagram/

[Author]

Replies