Temp gauge vs idiot light accuracy

[Jim&MaryJo]

Toured the Colorado Rockies last month. On steep grades, temp readings seemed to go a little high.

After a read of the Cummins and Coach manual, it appeared the Cummins ECU should light a "temp warning" idiot light at 205 degrees and further sets a "maximum allowable" temp at 212 degrees, which --if programmed-- would initiate an engine shutdown.

Put a call into Mark Hara (great help in the past on technical issues). Mark advised the temp gauge can be off by 10-15% (not sure if that's of range or value) and the ECU 205 setpoint would be more accurate (which never lit up on my trip).

AT this point, I'm cautiously concluding my temp gauge reading on grades of well over 205 was inaccurate and I never hit over 205??

I have 2 questions:

Has anyone seen an over-temp idiot light (or other similar Silverleaf indication) on when running?

And, there's an implication in my Cummins manual that the ECU will protect the motor under high IAT/temp conditions, regardless of FIG (Mike's moniker for pedal mashing). My last diesel had this feature and would override FIG and back off fuel/power. Anyone experience this after the idiot light lit?

Thanks for any replies...

[Jim&MaryJo]

Toured the Colorado Rockies last month. On steep grades, temp readings seemed to go a little high.

After a read of the Cummins and Coach manual, it appeared the Cummins ECU should light a "temp warning" idiot light at 205 degrees and further sets a "maximum allowable" temp at 212 degrees, which --if programmed-- would initiate an engine shutdown.

Put a call into Mark Hara (great help in the past on technical issues). Mark advised the temp gauge can be off by 10-15% (not sure if that's of range or value) and the ECU 205 setpoint would be more accurate (which never lit up on my trip).

AT this point, I'm cautiously concluding my temp gauge reading on grades of well over 205 was inaccurate and I never hit over 205??

I have 2 questions:

Has anyone seen an over-temp idiot light (or other similar Silverleaf indication) on when running?

And, there's an implication in my Cummins manual that the ECU will protect the motor under high IAT/temp conditions, regardless of FIG (Mike's moniker for pedal mashing). My last diesel had this feature and would override FIG and back off fuel/power. Anyone experience this after the idiot light lit?

Thanks for any replies...

[Danny Gayhart]

I can tell you from first hand experience you can't trust the idiot light. I though I had an overheating problem for years. After many calls to WRV and Cummins I solved it on my own. I bought a SilverLeaf to track temp. My idiot light would come on at 200! According to experts you can run a Cummins diesel all day long at 212, some say as high as 224.

SilverLeaf confirmed my suspicions. I now ignore the light. According to the SilverLeaf my temp never goes above 205. On the subject of shut down, Cummins has disabled that function in our coaches. Since you own a 34ft overheating is the least of your worries, try fuel prices!

Danny

[EngineerMike]

Jim, On my last diesel rig there were 2 temp sending units, one for ECU & other for temp gauge on the dash. Our light = 3 reporting functions (including Silverleaf & gauge) which could be accomplished on less than 3 senders. Presumably the ECU sender would be the more respected device. Under the theory that w/one watch I know the time, but w/two watches I don't, having more than one sender puts us in the position of having to worry which reporting path is working. I haven't determined whether we have multiple senders yet, but Danny probably knows.
Dan- IIRC you did your own Silverleaf install, no? What did you hook to for coolant temp input?

I hate being called an idiot. Specially by a dumb light.

[Danny Gayhart]

SilverLeaf gets data from engine and trans through diagnostic port under the dash. I run the pc based model.

Danny

[Ted III]

We have just returned from the Charlotte, NC pre rally where we were affordr a question & answer period with Cummins, Allison,Onan.,Silverleaf, HWH & Onan. I believe that Cummins considered an overheat @ 260?. I am still a poor believer in Silverleaf and I did not feel that their representation at Charlotte was very convincing.

[Jim&MaryJo]

This is all very confusing....

I would think the Cummins Manual would be "reliable"; it says the maximum "allowable" temp is 212.

I interpret their choice of words to mean the ECU takes preventative action at that temperature, which the manual indicates is a warning followed by a delayed programmable engine shutdown.

The Alpine manual says the idiot light comes on when the motor temp is out of range (185-205), which coincides with the Cummins manual.

Not stressing over this, just have an inquiring mind and wanted to validate what appears to be a temp gauge that reads high, apparently by ~10-15 degrees.

[EngineerMike]

Jim,
My Actia speedo has a preset and constant 2mph minimum, adding 2mph to velocity at all times (great for fuel economy while parked). Maybe your temp gauge has a similarly fictitious 12 degree "boot" in the reading.

[Jim&MaryJo]