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Discussion Starter #1 (Edited)
Hi all,

I've looked through the TSBs and various forums, but I can't come up with an answer to the trouble for my 07 300C AWD. Normally, the cooling fans would kick in to high when the car is warmed up and at idle, and run for several seconds until the temperature comes down (they're rather noisy on high, so it's easy to notice). Recently, I notice that the fans are not doing their thing and when I watch the temperature in the EVIC, I can see it climb up as high as 220 at idle when 204 would be normal.

At one point I had a light and the codes P0480 and P0481, which are left and right cooling fan motors. The light and codes have since cleared on their own. The fans do run on low.

Now, before you say my fans are burnt out, if I turn on the AC, the fans come on high right along with the compressor and the temperature stays right on the money. I checked the fuses and tried replacing the relays in the power control box up front anyhow, and they work perfectly fine - but only with the AC running.

I understand the stock settings in the FCM should be 205 for low fan and 215 for medium/high (because there is no medium speed on our cars). I don't have a Predator, so I can't try setting those values at lower points.

Is there anything further I can do to diagnose this, or am I stuck going to a shop that has a Starscan?
 

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It does sound like a stuck relay but it could be a break in the harness, a corroded connection or a broken pin in the connection to the fan from the harness. I'm not sure why they would only run with the A/C on but I strongly suspect an electrical or control problem here.

P0480 & P0481 trouble codes result from:

- Faulty fan control relay
- Fan control relay harness is open or shorted
- Fan control relay circuit poor electrical connection
- Faulty cooling fan 1
- Fan cooling fan harness is open or shorted
- Fan cooling fan circuit poor electrical connection

The system needs a voltage and continuity test from the front power module to the fans.
 

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Discussion Starter #3
Well, I find it odd that the same relays that power the high fans when the AC is on aren't being actuated on the coolant reading alone.
 

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Discussion Starter #5 (Edited)
Does anyone know if there is a menu on the Starscan to reset the FCM, or are there a bunch of stock parameters that must be set in it after a reset? I'm suspicious that the fan temperature settings have become scrambled, and if they have, what other settings may have been scrambled along with it. If I go to a non-dealer shop that has a Starscan, will they be able to figure out how to do a reset. I can not find a TSB that describes this issue.

You'd think that with the ELM OBD readers being so cheap, that someone would have programmed it for our cars as has been done with some Fords.
 

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Sorry I don't get on here much, but I should.

I have seen this a few times, mostly on Police Package cars. The FCM was the fix. If my memory serves me right, there is a fan state in the FCM scan tool data shows that the fans are in high mode, but it's not actually performing the task. I know one of the police garages had put 3 sets of fans and 2 CTSs on it.

Only way to know for sure is to let it idle out in direct sun, preferably up against a wall so the heat can flow up around it and watch the scan tool. Under normal conditions, you might see high speed fan mode for engine temp for about a 10-20 second window, so it's tough to pin it down.

The answer to the question "why do the fans run high speed for A/C, but for not engine temp high?" The vague answer I got was that the 2 relays are controlled in different ways depending on the BUS request/signal. If you look at the wiring diagrams for the relays/IPM/FCM, there are 2 different FCM control circuits labeled for the "High/Low relay control" and the "High speed". If you sit and stare at it for a while, you can understand in a Rainman sort of way how it works. (<<<not an engineer lol)

P0480 Fan #1 Control Circuit

FUSED (B+) CIRCUITS
(N201) RADIATOR FAN CONTROL RELAY CONTROL CIRCUIT OPEN
(N201) RADIATOR FAN CONTROL RELAY CIRCUIT SHORT TO GROUND
RADIATOR FAN CONTROL RELAY
FRONT CONTROL MODULE
 

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I considered the FCM as the problem but wanted to get closer to the relays and wiring first.

But it is conceivable that the FCM is the culprit and it would be a dealer who could say for certain.
 

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cooling fans

I was wondering if the cooling fans used on police and other hard service vehicles would work on a 300c? You can only buy them piece meal, because when mine failed at 59,000 miles, I could no longer get the whole module. When I was at jeep from 99-2008, we changed cooling fans like crazy. I have friends who drive Japanese cars and never deal with this problem.:salook::arms::biggrin:
 
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