Cooling fan rapid fast cycling

[Joshtheplumber1]

Fan comes on but does not have enough time to do any cooling. Off 8sec, on 4 sec, off 8sec, on 4 sec ………. Continues all during idiling. Not during driving. Not during coasting. We also discovered today if the AC IG off and the interior heat is turned on too high it continues fast cycling. The entire cooling fan system was replaced under warranty about 1 year ago and comes with a 2 year part and labor warranty. We tested a new 2022 van yesterday and no fast cycling. We have listened to a fedex delivery vehicle and no fast cycling either. Daytona Dodge Garage refuses to replace the assembly insisting it’s ok despite anyone who comes near the vehicle asking why is it doing that. Any suggestions? I thought thermostat maybe isn’t opening at idle and trapping excessive heat and fan try’s to cool it but does no good.

 

[RamRod37]

I would look more towards the Coolant temp sensor but they would normally throw a DTS for coolant temp but could be cause fans to go on/off like than also check relay

 

[crash68]

The cooling fan is turned on by more than just the coolant temperature, it's also driven by the oil temp and AC system.
That rapid cycling wouldn't be from a sticking thermostat, as mentioned above it's more likely a sensor issue.

 

[Oliver Closehauf]

That does not sound like a problem to me. I used to have SAAB 900 Turbos. Several of the tune up procedures required you to idle the engine with fans cycling. They would do exactly what you describe. On for a few seconds, off for about double. I never counted the seconds but it was about 4 and 8.
AC overrides the coolant temp switch and turns on the fan for better AC efficiency.
I think I was able to find a switch with a wider range (like 5 degrees) where it would kick off at a lower temp which reduced the cycling but that was a long time ago and I may be imagining that. If a computer is controlling your fan under normal conditions that wouldn't help you, but you might want to investigate that as a potential option.

 

[turkeybird56]

The cooling fan is turned on by more than just the coolant temperature, it's also driven by the oil temp and AC system.
That rapid cycling wouldn't be from a sticking thermostat, as mentioned above it's more likely a sensor issue.

Sensor or relay outta whack and/or going bad. Something not kosher there. Even the Humvee's did not cycle like that, and that fan was a roaring monster. All IMHO... I sure as heck would go to another dealership. Also, if you have a code reader, see if it has thrown any codes, any perm codes, any pending codes.