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kozakvod · 03-05-2021, **(Subject: Engine Fan )**

Good morning all!

Yesterday, I'm humming down the highway back to Dallas from Amarillo and as I always do just scanned my gauges and I know my coolant temp was sitting at or just about 180. A couple minutes later my engine fan comes on (There are no hills there to climb that would cause a 20+ temp deg rise that would cause the fan to come on) and after I stopped chewing on the seat because it scared the hell out of me I'm looking around at everything and see no issues anywhere on the gauges except that the temp gauge is just about 180, not 200+ and that's not right.

I'm thinking the pneumatic switch on the firewall went out (for the record that switch did go out no more than 6 months ago and I replaced it) and kicked the fan on and not looking forward to hearing the fan running for the next 300 miles to the house. Then as the temp dropped, the fan cut off. Behaving just as it would if heating up pulling a hill. It remained off, never acted up again until just before Decatur, same thing, exact same temps, comes on, temp drops, fan cuts off.

I'm thinking it's a sensor or switch or something. Any ideas or directions to run in?

Engine: 2013 cm2350

snailexpress · 03-05-2021, **(Subject: Engine Fan )**

(03-05-2021 )kozakvod Wrote: Good morning all!

Yesterday, I'm humming down the highway back to Dallas from Amarillo and as I always do just scanned my gauges and I know my coolant temp was sitting at or just about 180. A couple minutes later my engine fan comes on (There are no hills there to climb that would cause a 20+ temp deg rise that would cause the fan to come on) and after I stopped chewing on the seat because it scared the hell out of me I'm looking around at everything and see no issues anywhere on the gauges except that the temp gauge is just about 180, not 200+ and that's not right.

I'm thinking the pneumatic switch on the firewall went out (for the record that switch did go out no more than 6 months ago and I replaced it) and kicked the fan on and not looking forward to hearing the fan running for the next 300 miles to the house. Then as the temp dropped, the fan cut off. Behaving just as it would if heating up pulling a hill. It remained off, never acted up again until just before Decatur, same thing, exact same temps, comes on, temp drops, fan cuts off.

I'm thinking it's a sensor or switch or something. Any ideas or directions to run in?

Engine: 2013 cm2350

I think you have bad grounding to cab controller or somewhere as a result fan acting up and starter clicking.

Rawze · 03-05-2021, **(Subject: Engine Fan )**

just a blind guess...

could also be faulty wiring for or bad sensor for A/C pressure. Even if A/C is off, the engine fan will kick on if the sensor gets disconnected or reads high.

maybe pull A/C high pressure sensor connector and look to see if there is corrosion in the plug?

kozakvod · 03-05-2021, **(Subject: Engine Fan )**

(03-05-2021 )Rawze Wrote: just a blind guess...

could also be faulty wiring for or bad sensor for A/C pressure. Even if A/C is off, the engine fan will kick on if the sensor gets disconnected or reads high.

maybe pull A/C high pressure sensor connector and look to see if there is corrosion in the plug?

Rawze yes I failed to mention that the AC Comp was off.

kozakvod · 03-05-2021, **(Subject: Engine Fan )**

(03-05-2021 )snailexpress Wrote: ...
I think you have bad grounding to cab controller or somewhere as a result fan acting up and starter clicking.

Okay, showing my ignorance...by cab controller you mean what/where?

Waterloo · 03-05-2021, **(Subject: Engine Fan )**

I'm with Rawze on this one, as it was my first thought too, having been through this myself... I would suspect that AC high pressure sensor, not the sensor itself, but the wiring to it. Pull the split loom back on that wire harness from the sensor back, they tend to break from engine vibration over time or rub the jacket off the wires. Simple thing to check...

If the wiring is OK, and you have a PACCAR product, like Snail said, the flaky cab/body controller could be the issue. In a ProStar, it is located behind the kick panel on the driver side. No clue on other brands.

Curtisj28 · 03-16-2021, **(Subject: Engine Fan )**

Is fan clutch air on or air off? Could possibly be a bad fan clutch leaking air.

Chamberpains · 03-17-2021, **(Subject: Engine Fan )**

I dont know about this model engine but something to at least look at with insite... On older engines the fan will kick on like this without a CEL (check engine light) for higher oil temps and higher intake temps but under CEL thresholds.