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Cooling fan temperatures – DDEC V
Doing some digging around in the DDEC V parameters on my 2007 Marathon coach and thought I would clarify some things regarding coolant fan operation. I have always heard the coolant fans are set to kick on at 204 Degrees (F) for low speed and 208 degrees (F) for high speed fan. I decided to check that out in the DDEC parameters and discovered something very different. Just to verify, I checked a friends coach (2008 Marathon) and his parameters are set exactly the same as mine…….This is what I found for the 2-speed fan (typical of my era coach):
Low speed fan is set to kick ON at 199 degrees (F)
Low speed fan is set to kick OFF at 197 degrees (F)
High speed fan is set to kick ON at 208 degrees (F)
High speed fan is set to drop back to low speed at 206 degrees (F)
These fan temperatures are actually in degrees (C) in the ECU, but I have rounded and converted them to (F) for those of us that missed the metric train.
There is another interesting parameter that seems to be unused in the DDEC V eco-system. Apparently, you can enable the coolant fan to run at high speed (1:1 ratio with the gearbox) when Jake 2 is active regardless of actual coolant temperatuer. Jake 2 is switch position 2 or the highest engine brake setting. Might be nice to get a more effective Jake drag as well as more cooling while on Jake. I have watched intake air temperatures while on Jake and can tell you engine braking generates a fair amount of heat. Having the extra cooling might be nice.
Hope this helps someone chasing fan temps
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3 Replies
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Prevost told me for my DDEC3 60 series low speed is engaged at 200*f and high speed at 204*f . I installed a ScanGaugeD last winter and I can see high speed kick on at 204.
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Thanks Don. I’m sure EGR has something to do with the differences. Unfortunately, my coach is equipped with EGR.
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Those temps are programmable by a dealer. Initial Prevost Series 60 owners got scared when they saw the engine temps compared to their 8V92 175 degree readings so in some cases they had the temp set points reprogrammed.
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