The two Radiator fans are always running even at start up on a cold day. I have not had time to investigate as yet but I am assuming it is the temperature sensor located near the thermostat or a relay. No CEL on. Any thought on what it likely is and how to approach the trouble shooting?
Try a different ventilation function. They may turn off in another position when started cold.
The two fans are controlled independently–one runs at a certain temp, then if more cooling capacity is needed, such as on a very hot day or with the A/C on, the other one comes on. If they are both running all the time, I would suspect the temp sensor more than a relay. What does the engine temp gauge read at startup? Normal? I thought the computer made the decision to turn on the fans based on the coolant temp–the same sensor that shows the dash display of your engine temperature, but I could be wrong–there might be a 2nd one.
I did try some different ventilation positions. It did not seem to matter. But I will take another look at it.
The temp gauge seems to behave normally. I did not look exhaustively but it looked like the only temp sensor was on top of the water jacket near the thermostat. There are no sensors on the radiator. This is the 3.3L engine.
Is there a specific electrical module that controls the fans?
For some reason the car thinks the engine temp is hot or the A/C is on. It has been in the 20’s and 30’s this past week and the A/C has been disabled on this car for over 10 years.
It will be near 50 Deg today and I will see if that matters.
I need to dig out the manual but I doubt it addresses this problem directly.
Bad a/c pressure transducer. Down low, pass side between engine /radiator. Unplug it. Or change it
The a/c has actually been removed from this car. The compressor and some of the lines are gone. I will look to see if such a thing is even still present. I should have said removed vs. disabled.
All of the A/C equipment in that area of the car is long gone.
There are individual relays for the high and low fans. So going back to what Oblivion said it is likely not the relays. I will see if I can get codes pulled and see if that offers some clues.
If the heater controls are set in any defrost mode the
Fans will be on because defrost always runs the a/c.
Rock auto shows a radiator fan relay the looks like the fan controller in slightly newer models. It looks nothing like the other relays in the van.
I ran the codes using the MIL method and got.
12: Bat. disconnect in last 50 key cycles
33: High or low A/C pressure
66: No message from TCM or BCM (P1698 or P1695)
I disconnected the bat and reset the codes and restarted the car.
The fans did not come on right away and did come on when the temp rose as they should.
Rechecked the codes and had
12 and 33.
33 makes sense since there is no Freon in what is left of the system.
I am not sure what caused the problem to happened or was is has now gone away.
I also checked the resistance of the engine temp sensor cold and hot and both resistances seemed to be reasonable with the ranges in the Chilton manual.
Thanks to all who chimed in.
It’s possible the ECM thinks this car still has AC installed, and for some reason it thinks the AC is turned on, so it turns on the fans too. However if this fan always on problem just started, and the AC was removed years ago, that’s not likely a cause.
So … hmmm … the check engine light isn’t on right? And the check engine light does come on with the key in “on” but the engine not started? Right? Then I’m thinking this may be a stuck relay. Not an uncommon thing. What happens is the current to make the fan spin goes through a coil of wires in the fan motor, and when this current it cut off, the magnetic field collapses and creates a big voltage spike, which can jump across the relay contacts. This happening time and time again can eventually sort of weld the relay contacts together, cause the relay to stick in the “on” position. Someone with appropriate auto-elec training could determine if the relay was stuck on or not.
The 33 code is normal based on the circumstances of having the A/C completely ripped out, I think. A lot of Mopar cars of this vintage throw a 12 code all the time, regardless of whether the battery was disconnected or not. It is perhaps a bug in the firmware. This code doesn’t normally turn on the check engine light, I think. You might check your battery terminals for tightness and corrosion though–if the battery voltage drops very low during starting (which a poor connection can cause), this code can be set.
The 66 is a bit worrisome–if the ECU and the BCM aren’t communicating properly, it could possibly be causing all sorts of problems. Since you’ve reset the codes, I’d see if that one comes back.