2004 S40, in otherwise very good condition.

There are 2 radiator fans - drivers side and passenger side.
Upon moving the ignition key to the "III" position (without starting), both fans turn on, and will stay on if the car is started.

Whether the car is started or not, if the ignition key is put back into the "I" position and key removed, one fan turns off, but the other stays on, and remains on for about 15 minutes, or until the battery runs down, whichever comes first (since the car has not been driven lately, it's usually the latter).

Searching through this forum (and elsewhere), the consensus solution was to replace the engine temperature sensor, which was done (along with the thermostat). No improvement.

Further reading suggested cleaning the MAF sensor. It appeared to be perfectly clean, but I cleaned it anyways. No improvement.

The only way I found to "fix" the problem was to remove the "Radiator Fan Speed 1" relay. Thinking this might be the source, I swapped it with one of the other (identical) relays, but the problem persisted.

I'd be very grateful for any tips on how to further troubleshoot this puppy.
Many thanks, and have a happy New Year.


BTW: How bad an idea is it to simply leave the "Radiator Fan Speed 1" relay out?
Like "it's not advisable", or more like "you must be crazy".
With it removed I let the car idle for quite some time in my garage, and the temperature gauge didn't go above mid range...

 

If you are located in a cool climate you may be fine for a while. It's been in the 30's here and my temp has not reached over 205°, the fan doesn't come on until about 216°.

 

I can't really offer any troubleshooting tips but I can share my recent experience on the radiator fan as I just replaced mine less than a week ago.

Just a few days before the fan never stopped running on my V70 2004 and eventually drained the battery. I had to jump start the battery in order to drive but the fan still kept running. The same cycle went on. I decided to take it for service and check the relay. However, and unfortunately, I had to drive over 100 miles in order to come back home. After a couple of hours drive I started to smell a plastic burn odor so I pulled over and after opening the hood, I noticed that part of the fan was actually on fire with flames coming out. I had to replace the entire fan assembly with a new one. Now my car drives fine and the new fan almost never comes up. I realized that for months the fan was running much more than needed. It sometime took 15 to 20 minutes for the fan to turn off after stopping the car. When I drove last week, the fan overheated since it was running consistently. This led to a fire. I would keep a close eye on what's going on with your fan but a fan that can't stop running could be a recipe for disaster. In my case, replacing the fan assembly was expensive and drastic but if it's not the relay, it might be the fan.

 

Interesting.
My S40 has two fans, both of which run all the time while the engine is on.
Is that normal?

If it's normal, then there probably isn't a problem with spontaneous combustion.
On the other hand, if it isn't normal, then there are more serious issues to deal with.

It doesn't seem like the fan itself could be the source of the problem, since it doesn't get power unless the relay delivers it. More likely it's upstream of the relay.

 

Update 2:
The sucks. It died in 50 miles and the fans stopped, leaving the engine overheated. Anyone knows if Land Rover dealership sells compatible model and what's the call number?

 

Hi

You can try whit it , at least I know it has been working for more than 5.000 km in an XC70 2010 3.2 engine
https://www.ebay.com/itm/292613368330

 

That doesn't appear to be the right part number for any S40 / V50.

 

No , it is not for S40, I was answering to Fiedel