Hi y'all
I am currently in the process of diagnosing why the radiator fan on my 2004 XF doesn't work, when I apparently causes another issue. First, I jumped the fan motor directly, which actually works, and then checked the 50 amp fuse with an ohmmeter, which seems fine. During this process, I now have a situation where the horn comes every time I start the car. Nearest I can conclude is I somehow jarred the RCM while checking the fuse. The negative battery cable was off when I did all of this, and I unbolted the fuse before checking with the multimeter.
Any thoughts!

 

Most likely the fan regulator.

 

Maybe something is shorting the horn relay in the RCM?
The horn relay fuse is #6 in the picture. Try taking that out and see if the horn stops.


FUSE # AMPs USAGE
1 15 Traction System Relay
2 15 Oxygen Sensors, Air Pump Relay, EVAP Purge Solenoid, Charcoal Canister Shutoff Valve, Air Pump Switchover Solenoid, EGR Solenoid (except SRT), Supercharger Clutch (SRT), Short Runner Valve Solenoid (except SRT)
3 15 Power train Control Module, Fuel Injectors, Camshaft Position Sensor, Fuel Pump Relay
4 40 Air Pump Relay
5 15 Fuel Pump Relay
6 15 Horn Relay

 

I found and fixed the horn issue! Somehow, a mouse or small rodent managed to get into the main electrical box that houses the RCM(the lid was on tight, so I don't know how it would have gotten in there). The animal chewed a bunch of wires on RCM connector "E", which goes to the horn relay. I had to use a ton of electrical tape, as there was so much wire chewing. I took a look at the RCM, and it appears to be in decent shape, with no signs of solder burns.
Now, I need to find a pest deterrent for my car!