Heat and ECMs
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