Hey guys, new member here. I have an 07 1500 HEMI and recently my condenser fan gave out. I've searched all over the forums and I know that this is a common problem with these trucks and usually replacing the fan does the trick. Yet my problems lies in the fact that I have 12V sitting on the harness all the time. It reads 12V no matter what I do....and I mean any combination of climate control settings, everything completely off...it doesn't matter. If ignition is set to ON and/or the engine is running, the fan would run non-stop. I really want get this fixed but I'm worried that if I buy a replacement fan that it will run constantly until it burns up. Should the fan stay on? Please help....Texas doesn't know what winter is and I need my AC back. Thanks in advance for any info.

 

The fan motor is energized by a relay in the power dist. box (fuse box). Look at the map on the inside of the cover, theres a good chance that you have a relay the is bad---the contact points are fused together. Thats the best place to start anyway, after that it could be something in the control center, defrost control, or front control module (computer) attached to the power dist center, figure out which relay it is, pull it, see if 12v goes away, if it does go away, switch another relay into its place, see if it stays away, if not, good chance its a computer problem

 

At the same time, maybe 12v is constant and the ground is switched? IDK as Ive never checked it.

 

VERY likely. My 300C has a whole buncha switched grounds. Not sure why Chrysler did that.

 

Chrysler isn't the only mfg that uses switched grounds. In CANbus systems voltages aren't always referenced to a straight grounds or 0 volts. Some of what to appear to be switches in automotive can actually be sensors used to control circuits where the reference is a variable.

 

Thanks for the quick response guys. I guess the next step is to work backwards from the fan but where is the relay? Most relays that I've seen in vehicles look like little black boxes but when I open the fuse/relay panel next to the battery, I don't see anything like that. Some people have even told me that my truck doesn't have traditional relays but I'm not sure what to make of that.

 

Update: So I downloaded the 06 service manual -thanks weedahoe- to find out more about the wiring and the diagrams for the condenser fan don't show a fuse or a relay. I tried to follow the subsequent diagrams and it sends me to 4 other pages and then brings me back to the original one that I started on. Somehow it suggests that it "magically" comes from the C8 harness connection on the back of the power distribution board but it wont tell me where it originates from. I feel like I'm chasing my tail on this one.

 

When I responded above, I had gone through an FSM for my 2005, and forgot that the 2006 was the first year for the canbus protocol, so it could very well be a common 12v and switched ground. I did in my FSM, verify that the fan is fed through a relay and is a switched 12v and common ground. Look in the regular "wiring" section of your FSM---if this section exists, I started in the A/C-heat section and eneded up looking under general wiring section

 

I believe it is actually switched from the PCM like everything else since 06.

 

So I have good news and strange news. First the good news, the condenser fan works! Now the strange part about how it got fixed. I traced the wiring back to the fuse panel and everything checked out. ie. resistance checks proved that the wiring was good. However the PCM was still closing that ground. I said what the hell and bought a new fan motor from O'reillys for only 25 bucks. Way better that 75+ for a whole new assembly. Long story short is that since the PCM showed the fan active when it died, somehow it stayed in that condition. So when i hooked up the new fan and tried it out, it ran for a few seconds and the turned off. From that point on it has been working exactly like it should and my AC works great now. Thank you guys for all of your help and advise.