Bad temperature gauge or sensor?

[Meanwhile]

After unplugging the high pressure sensor, I dove over 300 miles. The only time the fan came on was when coolant temperature reached above 200 degrees. Thanks again for your help with this!

[RustyWood]

(06-05-2020 )Meanwhile Wrote:  After unplugging the high pressure sensor, I dove over 300 miles. The only time the fan came on was when coolant temperature reached above 200 degrees. Thanks again for your help with this!

Interesting, I noticed the last month or so when my truck was running, that my fan seemed to be nearly always running as well, I think I'll look into trying this also and see if it cures my fan running so darn much. Thanks for this thread !

[Meanwhile]

I bought AC parts Monday and got both the high and low pressure switches for the expansion valve. Thursday, before I could get the new parts put on, my fan would not shut off. I messed with it for a while and one of the guys in the boss's shop was looking at it too. He thought it was the fan solenoid so later on I got one of those also. I ended up driving close to 400 miles and the only time the fan shut off was when I shut the truck off.

I did NOT put the high and low switches on the expansion valve, yet. The AC is charged and seems to cycle well with the old ones in there. The fan solenoid was not the cure. The other guy in the boss's shop believes that the fan hub is bad BUT after reading posts here I'm not convinced. I took the air line off at the fan hub to make sure the was air running through it and it does but, only when the engine is off and key is on. When the engine is running there is no air. With the air line hooked to the hub, key off the fan won't move, Key on, the fan spins freely. Am I on the right track here?

I hooked Insite up and fumbled around a bit, I need to get more familiar/learn how to use it.

Going off the list Lonestar10 posted earlier on:

Water temp was about 180
Intake temp was about 195
Oil temp, from what I remember was about 200

I'm thinking my next step is to check the Fan override switch on the dash and look for any rubbed or broken wires under the hood.

[Chamberpains]

Intake temp of 195° is awful high. On a hard pull my cm870 would only reach 160ish. Any other time it floats 20-50° above ambient temp. Depending on if I was using any throttle. When was that temp taken?

[Meanwhile]

I was parked with the hood up when I was looking at that temp, idling about 900 rpm and fan on. I'll double check that today to make sure.

[Meanwhile]

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.

[Rawze]

when is the last time someone took apart the front end and cleaned out all the dust and depris between the CAC and radiator? -- cleaned out all the dirt from the fins? etc.

could be the radiator or CAC full of dust and dirt, blocking air flow.

[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.

this would highly depend on the brand, make and model year engine and truck. - not all trucks have the same programming or settings for this, and some trucks do not use the engine fan at all to lower high intake temps.


I.E.. Don't take what you see on those SAE generic sites and books, etc.. as any kind of final word. Many of those docs can be misleading. Sometimes the info found there is helpful, but sometimes it can lead you into the wrong path too.

[Meanwhile]

I wondered about dirt and junk in there also. I kept my old intake sensor, cleaned it up and put it in just to see what the readings were. At normal temperature, water temperature of 180ish and 850 rpm, intake air temperature was around 130 degrees. Dropped down to 700 rpm idle it was 93 degrees and outside temperature here is mid 80’s today. The fan still runs. I put the AC high pressure sensor on and the fan still runs.