Bad temperature gauge or sensor?

[Waterloo]

Could the fan clutch simply be stuck? I had issues with mine after it sat, I could not break it loose for the life of me, and it was a new fan clutch, so I figured it still had to be good...

So, I rigged this little tool up... FleetPride hooked me up with the 1/4" air line and fittings, I think it all cost around $15 or so...



I hooked the push pull fitting to the air line running off the solenoid to the fan clutch, and hit it with a full blast of air from my little Lowe's 90psi compressor. POP! That is all it took, may be worth a shot. The motor was NOT running when I did this. CM-871

[Meanwhile]

With the engine off, if I turn the key into the on position the fan will release and spin freely. The solenoid has power, I hear air release when I unplug it and Insite shows the fan as being on. Now I’m looking for broken or worn wires.

[Chamberpains]

Sounds like you caught a faulty sensor with the intake temp. So thats good. It may have been some of your problems.

I see you said you bought the high and low pressure switches on the Expansion valve. My t660 has both of those and the fan high pressure switch on the low pressure AC line close to the AC compressor. That is the 1 that actually turns the engine fan on and off according to what the AC demands. I dont know if your truck is wired this way but Did you replace that one too and check its wiring.

[Waterloo]

On my ProStar, the wire from the high pressure switch, roughly 6 inches or so from the sensor itself, has broken twice on me, I assume from engine vibration. Peel back the split loom and start there. That is assuming it is up there on top by the radiator.

[Meanwhile]

I haven’t changed that one yet but it’s looking like I will be. I’ll check locally for that one, maybe I’ll get lucky tomorrow and not have to drive an hour and a half out and back to get one.

[Meanwhile]

I’ll check that one next. Thanks guys!

[fargonaz]

At 400K you could probably use a fan clutch/rebuild, could be leaking past the seal in there.

[Meanwhile]

Found a pressure switch today for $15 and everything seems to be back to normal. Ordered an intake switch also. Thank you for your input and assistance with this!

Fan clutch rebuild will also be added to the list, Thanks!

[Rawze]

(06-28-2020 )Meanwhile Wrote:  I just found this on an ASE Diesel diagnosis page.

High Intake Manifold TemperatureECM will turn the engine cooling fan on at 190 ºF. A 20% power derate begins when the mainfold tem-perature reaches 210 ºF. The derate increases to 40% if the temperature remains high.

I'm gonna go check my Intake sensor and see if it's covered with junk.

I was looking thru a CM2250 file today for someone and thought about this post you made while going thru it.

Here is how this persons CM2250 is set with regard to engine fan use and CAC temps...

* From factory, the engine fan is requested to come on if the CAC estimated inlet temp is above 166+F.

* For trucks equipped with a with variable speed engine fan, 33% fan speed is requested at 166-F, 66% at 184-F, and 100% at 199F.

Cummins programming refers to it as "Charge Temperature".

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I am not implying this is your issue, but just thought I would follow up with that assumption/question that you posted earlier.