2007 Chrysler Pacifica 4.0L, cooling fan runs constantly

Joined
Mar 2, 2004
Messages
4,410
Location
Kentucky
I have a 2007 Chrysler Pacifica 4.0L V6, about 195K miles. When I last went to drive it I noticed the cooling fan started running at startup and it doesn't stop until the car is shut off. This was on a cold start with no A/C. I can reproduce it at every startup.

I plugged in my scan tool, I don't have any stored codes or CEL. Reading live data with engine running (fan on), all temps are normal (coolant temp, ambient air, trans oil temp, A/C not engaged, etc). The "low speed fan commanded" and "high speed fan commanded" variables are both false, so it appears the PCM is not asking for the fan. What's interesting though is that the fan won't run with the ignition switched to on. You actually have to start the engine and there is about a 2-3 second delay before fan kicks on.

Curious if there are any common culprits for this condition before I go chase down wiring diagrams and do a deep dive into the fan circuit. Appreciate any insight!
 
IIRC it has a pwm module/fan speed controller.....Scope the PWM trigger at the module & see what the duty cycle is.

Per Alldata....
"The solid state radiator fan relay is controlled by the Powertrain Control Module (PCM) by way of a Pulse Width Modulated (PWM) signal. The relay control circuit supplies a 12 volt signal to the PCM. The PCM then pulses the ground circuit to achieve fan on time. The relay provides a voltage to the fan motors which is proportional to the pulse width it receives from the PCM. The duty cycle ranges from 50% for low speed operation, then ramps-up to 100% for high speed operation. This fan control system provides infinitely variable fan speeds, allowing for improved fan noise, A/C performance, better engine cooling, and additional vehicle power."

Or just throw a new module/relay at it.....
 
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