2003 Lincoln Town Car Cooling Fan runs constantly while engine running

Please fill out the following to ask a question.

MAKE: Lincoln
MODEL: Town Car Signature
YEAR: 2003
MILES: 51,000
ENGINE: 4.6 liter
Just picked up a 2003 Lincoln Town Car from the original owner. It is an unmolested, all original private owner Car.

Problem is, at least I think it's a problem, is the cooling fan runs constantly while the engine is running.

A/C is off.

Car does not overheat, antifreeze is full. Heat works too.

Temperature Gauge never goes past the middle, whether in stop and go traffic, or on the highway. Or local errands.

Any advice appreciated, thanks.


Staff member
Find the fan relay and pull it out, see if that stops the fan (then put it back in, this for a test only). If pulling the relay stops the fan, then we know which direction in the system to precede; from the relay to the fan or from the relay back to the PCM. Oh, and be sure to try swapping in a similar relay from a different location in the relay/fuse panel... it may be just a stuck relay.


Wrench. I help when I can
Since we know the fan is not running engine off, we know this is not a direct short. The wiring shows hot at all times, so if it was a direct short, it would be on at all times until battery runs out.

So thing is to know, does it come on key on engine off, or only engine running. If it is engine running, we have to know why. This is a PCM driven fan via various sensors such as A/C and ECT various sensor.

The idea of a stuck relay is in principle a good idea. But if it were stuck, it would run all the time, even with the key in your hands.

This also being known, fan runs even with AC off. SO my idea is to try to disconnect the ECT sensor first to see if that shuts down the fan.

Pull codes first. If any codes are present record them, as if you start disconnecting sensor and connectors, you may get false codes frrom your testing. Better to note any codes present before starting to trouble shoot.

Ford gives a very simple and non comprehensive wiring of the fan circuit. Not much help there. A scanner will be of the utmost help. If not, bear with me, we will find this solution fast enough.


Wrench. I help when I can
On this model, only one electric fan yes? Not two, example one for for high speed and one for low speed. Only one? Yes?


Wrench. I help when I can
So why is the PCM commanding the fan on once the engine is running? Does the fan turn on AT MOMENT of engine engagement?


Wrench. I help when I can
This is me thinking/writing out loud. I do this to help me sort out different questions within my self. So we know the gauge in dash shows a no heat condition.

I am going to go on two assumptions which I know have not been proven to be correct yet, but will move on this assumption.

I will assume ECT if good as it gives cluster info. Fan shuts down once engine is off, meaning the relay is cutting out, meaning it is not stuck or fan plug has not melted to the point to give a direct path bypassing the PCM. (which BTW is a known issue on these fords/lincolns) The only other thing that controls that is the PCM.

So to rule out the AC, removing the AC main fuse would rule that module out also. This will code probably, but for the sake of trouble shooting a bad PCM, I think it important to rule out the HVAC module as a possible culprit.

Once that is done, you might just be looking at a bad PCM driver that has grounded that circuit for good once the engine is on. If this turns out to be the case, you can by pass that with a patch if you want.

To 100% rule out the ect sensor, a scanner is a must here. But my doubts do not lye there.

So, to repeat myself, fan off, engine off?

Fan on once engine starts? Yes. Even if cold? yes?

This is going to be a PCM control issue and should be treated as such. Plz confirm no codes before diving into this, it would help greatly.


Wrench. I help when I can
I have done this before on older models, but would think it would apply to you.

If we find that the PCM is at fault and is grounding the fan circuit to be on all the time when engine is on, a thermal switch can be introduced to automatically swtich that fan on depending on temp the thermal switch is seeing.

I have installed a few of these to save customer the expense of a new PCM. All you need is a thermal switch, some machining skills and some tubing, or you can by a t-adapter which will fit your rad hose leading to the t-stat. The bypass should look something like this. 685229352_8cacb35978_o.jpg


Wrench. I help when I can
You can buy an inline adapter and a thermo switch that threads in to there. You fan should have a two pin connector. It fits together easy as pie and once the thermo switch reaches a target temp which you will determine by your region to set off the fan, you won't have to worry about it.

The other option is wiring in a direct switch which requires you to monitor engine temp at all times and flick the switch when you see temps rise. But I only did that for my drag cars cuz I didn't like my fans sapping power when not needed. Here is a link to what an inline adapter should look like. I make my own cuz I have tools and skills. But this is a worthy option for someone who does not have access to some tooling.



Wrench. I help when I can
Also, someone here may be able to correct me, but I think the relay is integral to the fan module.

I am NOT seeing the relay for rad fan in power distribution/junction box and my memory, even though failing, reminds me the relay was in the fan module integral to fan assembly. Which like I said before, tended to melt alot on these town cars and crown vics. But again, I need confirmation from a colleague here to say for sure.


Staff member
Good points and questions nickb2, and the schematic helps me understand this system better. I was thinking too simple.

Yeah, probably no relay with that fan control module, and isn't it PWM from the PCM? I would be suspicious of that fan module, I think we have had other threads where that has failed on Ford vehicles.

OP, do you have an electrical multimeter and the skills to use it? We need to see what the voltage is on that wire 229 (RD/OG), you should "back-probe" it using a sewing needle into one of the connectors, with harness still connected.
Hi and thanks for the replies.

The fan runs when engine running, not when key is in on position with engine off.
KOER; yes...KOEO;No.

To confirm:
1)Fan on once engine is running, even if cold.
2)Car has only one electric fan.
3)Fan stops, once you shut the motor off.

I have access to a generic obd 2 scanner,
...will this be sufficient to pull for the type of code triggered by the fan ? No lights on on the dash.

Which relay can I swap out under the hood. To see if it's a bad relay? I don't want to cause another problem by swapping out a wrong amperage relay.

Thank you again.


Hero Member
This is sounding like a common problem and the aftermarket seems to offer a workaround. My friends at RockAuto.com show a Hayden 3651 "fan controller"
. It seems you might be able to identify the power that the Fan Module is sending full time to the Fan Motor, and install a device like this in line. My first thought was "substitute the relay" too, but I soon found out from the guys with experience that such isn't the case. "Module" which is of course "serviced as an assembly" instead. RockAuto's Fans seem to include a "Module."