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​Heat and ECMs

By Fernando DeMoura

April, 2019

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The last three articles I wrote have been about dealing with the heat created when an engine makes power.

Heat or extremes in ambient temperature can be a problem for ECMs as well. The DDEC III and DDEC IVs are often used in military applications and the components in these ECMs are designed to endure temperatures as low as -40 degrees Fahrenheit and as high as 250 degrees Fahrenheit. The DDEC V has some of the same parts but the case and circuit board design leave it more susceptible to damage due to rapid thermal expansion and cooling. On a DDEC V the circuit board is glued directly to the inside surface of the ECMs aluminum skin. The sheet of aluminum is about 2 millimeters thick and transfers heat quick. This works great for internal cooling but that rapid heat transfer goes both ways. When the BGA pads connected to the 32-megabyte microprocessor running next to a Series 60 cools rapidly because the DDEC gets splashed with water the rapid cooling can cause the fine traces to peel off and delaminate. Before I ever understood why I heard of stories of DDEC Vs that wouldn’t start unless they were heated with a torch first. Sometimes a little heat brings the detached traces back together, but it also makes the delamination worse, so I never recommend doing that. On a DDEC III this isn’t very common. The older DDECs are built heavier. These boxes have more aluminum, thicker cases, and thicker traces with more space between the traces for thermal expansion. 

That’s why I was surprised when I heard the story from the owner of this P23518645 DDEC III. He recently bought this ECM from one of the bigger Texas ECM rebuilders. He had them send it up to Edmonton, Alberta and he discovered his box would not start when the ambient temperature fell below 50 degrees Fahrenheit. I didn’t bother to ask him why sent it to me instead of the guys he bought it from in Texas. They probably assumed it was a fueling issue and didn’t believe him. Cold start issues are usually a fueling issue but after I cooled it to about 40 degrees Fahrenheit and tested it, I saw exactly what he saw. A dead ecm. Given he’s in the middle of Alberta and it’s going to be a while before global warming…or is it global cooling? I think it’s back to global warming again… but just in case I’d better fix this box. 

After removing another “Warranty void of removed” sticker I took a few shots through a thermal imaging camera. It can only see in Infrared…like the Predator. Areas that give off the more heat glow red while the colder areas stay blue. In this other photo the ECM was slowly warming up from 48 degrees Fahrenheit and sure enough. I turned the ignition to the on position and nothing. Everything stayed cold and amperage draw was almost nothing. The next shot is around 60 degrees Fahrenheit. Here you can see the ECM starting to come back to life. I found some broken traces, made some repairs, and am now running some automated tests while the ECM freezes and thaws over the weekend. If all goes well this box will be back in service next week.

Fernando DeMoura

Diesel Control Service

Phone 412-327-9400

ebsite: www.dieselcontrolservice.com

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