Fan runs continuously

[Jeep in Ethiopia]

Hey everyone,

I'm thankful for this forum already. I just joined today. I'm not particularly mechanically inclined. And here I am in Ethiopia driving a Jeep Wrangler TJ 2006. Often, there are no parts here and/or no mechanic who knows what to do with a Jeep. So, I'm mostly on my own (good way to learn).

Recently, my radiator fan has been running continuously. When I start the engine, it runs and never turns off. I've limited driving to 4 day a month in short stints right now as a result. I've replaced the two fan relays. The mechanics here (don't laugh at them or my own ignorance) suggested it was the circuit fuse for the fan. So I swapped that out as well. Anyway, those three parts replaced makes no difference. Fan still runs without stopping, ever.

So, would it be the temp sensor that I should check next? If so, where can that be found on the Jeep Wrangler TJ 2006?

If you'd all try looking at something else, I'd appreciate feedback in that regard as well.

I've included photos of the parts I replaced. And given that this is my first post, I've included a photo of my jeep here in Ethiopia (that's the rarest wolf in the world walking past my jeep; yes, it's the critically endangered Ethiopian wolf, not a fox).

I get to track lions and all kinds of amazing wildlife here as a result of my baby (Jeep). Need it back up and running smoothly again.

Thank you all so much!

 

[Steel City 06]

I don’t have experience with the electric fans, but here is a good place to start. Download the FSM for your TJ.

https://wranglertjforum.com/threads...ice-manuals-fsm-technical-documentation.4618/
There should be some wiring diagrams that can help troubleshoot if you know what you’re looking at

 

[Jeep in Ethiopia]

I don’t have experience with the electric fans, but here is a good place to start. Download the FSM for your TJ.

https://wranglertjforum.com/threads...ice-manuals-fsm-technical-documentation.4618/
There should be some wiring diagrams that can help troubleshoot if you know what you’re looking at

I'm lost when I look at these. Sorry, a bit helpless I guess. In the service manual doc for my 2006 TJ, would page 339 or maybe 355 be where I'd start? Sorry, just completely lost on what to do.

I asked my mechanic friend in the US if he thought it was the temp sensor. He said, " it's possible, there should be two sensors, one for the dash gauge and one for the fans, disconnect it and see if they stop, if they don't look at the dash gauge and see if it has went down to cold, if so it's the other...the fan thermistor is usually located in the cylinder head while the one that signals the gauge is almost always by the thermostat housing, close to where the top radiator hose goes into the engine..."

Even those simple instructions confused me as I'm not sure what I'm trying to figure out nor the process for removing those. Logic seems to dictate that removing those while the vehicle is running is a really bad and dangerous idea. :/

 

[Steel City 06]

I'm guessing you have a 4 cylinder engine? (The 6 cylinder models have a mechanical fan clutch.)

You could shut off the engine and unplug them and restart to test. I certainly wouldn't want to reach in by a moving fan or belt and risk serious injury

 

[Jeep in Ethiopia]

I'm guessing you have a 4 cylinder engine? (The 6 cylinder models have a mechanical fan clutch.)

You could shut off the engine and unplug them and restart to test. I certainly wouldn't want to reach in by a moving fan or belt and risk serious injury

Yes a 4 cylinder.

What would unplugging them accomplish? I guess I'm assuming unplugging them would cause the fan to not work regardless. So, can you help me figure out what unplugging them accomplishes? What am I trying to figure by doing so?

 

[Steel City 06]

Yes a 4 cylinder.

What would unplugging them accomplish? I guess I'm assuming unplugging them would cause the fan to not work regardless. So, can you help me figure out what unplugging them accomplishes? What am I trying to figure by doing so?

It would basically tell you if they are the cause of the fan being on. If the fan doesn't run without them, it may be a bad switch. I'm not familiar with how they're wired (fail open or fail closed), but there is probably a way you could test the switch with a multimeter

 

[Jeep in Ethiopia]

It would basically tell you if they are the cause of the fan being on. If the fan doesn't run without them, it may be a bad switch. I'm not familiar with how they're wired (fail open or fail closed), but there is probably a way you could test the switch with a multimeter

So, if things were normal, unplugging those sensors would not change the status of the fan running? They would continue running with the sensors (either one) not being connected?

I think part of this comes from my complete ignorance of their functions and so not knowing how they ought to operate causes even further confusion during diagnostics.

Thanks so much for your help right now.

 

[Steel City 06]

My guess is that the fan switch acts like a basic thermostat. Once the coolant hits a threshold temperature, it would close and allow current to pass to the relay, turning it on. Once the coolant drops below a threshold temperature, it would open and turn off the relay to the fan. So it seems like it would be a basic on-off switch. Though I could be wrong

 

[AMS417]

My guess is that the fan switch acts like a basic thermostat. Once the coolant hits a threshold temperature, it would close and allow current to pass to the relay, turning it on. Once the coolant drops below a threshold temperature, it would open and turn off the relay to the fan. So it seems like it would be a basic on-off switch. Though I could be wrong

I think you are on the right track. I would assume, logically that the switch would fail closed for safety to prevent overheating. If equipped with a/c some vehicles use the PCM to turn on the cooling fans when the a/c is on also. I would remove the connection from the temp sensor, start the engine and see what changes. Process of elimination. Do the simple (inexpensive) stuff first. Testing the theory is free, and a good place to start.

 

[Jeep in Ethiopia]

My guess is that the fan switch acts like a basic thermostat. Once the coolant hits a threshold temperature, it would close and allow current to pass to the relay, turning it on. Once the coolant drops below a threshold temperature, it would open and turn off the relay to the fan. So it seems like it would be a basic on-off switch. Though I could be wrong

When you said "Fan Switch" did you mean Temperature Sensor? Are they the same?

I'm concerned about starting the vehicle with one of those two sensors (or switches) unplugged. Doesn't one of them tap directly into the coolant line?

 

[Jeep in Ethiopia]

I think you are on the right track. I would assume, logically that the switch would fail closed for safety to prevent overheating. If equipped with a/c some vehicles use the PCM to turn on the cooling fans when the a/c is on also. I would remove the connection from the temp sensor, start the engine and see what changes. Process of elimination. Do the simple (inexpensive) stuff first. Testing the theory is free, and a good place to start.

OK, I just replied to Steel City 06 asking about disconnecting one of the sensors and starting the car. Clearly I'm ignorant of all this then. You disconnect as opposed to unplug or remove? That way it is safe to start the vehicle even though it isn't connected?

And then, if the fan is continuously running still, what should I conclude?
Whereas if the fan is not continuously running, should I assume the temp sensor is bad?

Now, to find these items

Thanks so much! I'm going to learn this stuff if it's the last thing I do!

 

[Steel City 06]

It might throw a CEL at worst. As long as you don’t physically remove the sensor and let the coolant pour onto the ground, you should be fine. If you notice the engine overheating, stop the test. It would likely take a while for it to overheat, so you should be fine running the engine without the sensor connected temporarily.

 

[AMS417]

OK, I just replied to Steel City 06 asking about disconnecting one of the sensors and starting the car. Clearly I'm ignorant of all this then. You disconnect as opposed to unplug or remove? That way it is safe to start the vehicle even though it isn't connected?

And then, if the fan is continuously running still, what should I conclude?
Whereas if the fan is not continuously running, should I assume the temp sensor is bad?

Now, to find these items

Thanks so much! I'm going to learn this stuff if it's the last thing I do!

Need someone more knowledgeable to explain. The temp sensor may be acting as a switch to control the fan by way of the relay. Making it both a sensor, and a switch. It may also be sending signal to the PCM to control the relay. Not 100% sure on the 4 cylinder. Let me look at the wiring diagram.

 

[Jeep in Ethiopia]

It might throw a CEL at worst. As long as you don’t physically remove the sensor and let the coolant pour onto the ground, you should be fine. If you notice the engine overheating, stop the test. It would likely take a while for it to overheat, so you should be fine running the engine without the sensor connected temporarily.

Thanks. Yeah, the check engine light and check gauges lights are both stuck on. They clear them and they both immediately come back on. The mechanics here in ethiopia can't figure it out. They don't know what to do. They don't know this kind of vehicle and are extremely limited. Any parts I have to ship into the country as well. Tough situation only made worse by my own ignorance.

 

[AMS417]

Ok, just a hunch here but I think this is what is going on. The temp sensor is sending data to the PCM, the PCM is controlling the gauge and the fan relay. Disconnect the wire to the temp sensor and tuck it away so it doesn't get sucked into the belts or anything. Disconnect your battery for a few minutes. Reconnect your battery, but leave the temp sensor disconnected and start the vehicle. See what happens. I think your temp sensor has failed. Could be a bad PCM also, but the sensor is cheap to replace. Start there.

Also make sure both fan relays are re-installed. It has two for high and low speed fan operation.

 

[Jeep in Ethiopia]

Ok, just a hunch here but I think this is what is going on. The temp sensor is sending data to the PCM, the PCM is controlling the gauge and the fan relay. Disconnect the wire to the temp sensor and tuck it away so it doesn't get sucked into the belts or anything. Disconnect your battery for a few minutes. Reconnect your battery, but leave the temp sensor disconnected and start the vehicle. See what happens. I think your temp sensor has failed. Could be a bad PCM also, but the sensor is cheap to replace. Start there.

Also make sure both fan relays are re-installed. It has two for high and low speed fan operation.

Awesome. Will do.

How might I go about finding the two temp sensors? Again, full-on ignorance. Been trying to look it up online to no avail. Is there an illustration that might show where they can be found on the 2.4 Wrangler TJ 2006?

How difficult to replace the power control module?

 

[AMS417]

Awesome. Will do.

How might I go about finding the two temp sensors? Again, full-on ignorance. Been trying to look it up online to no avail. Is there an illustration that might show where they can be found on the 2.4 Wrangler TJ 2006?

How difficult to replace the power control module?

I believe the connection you want to remove is here:

Pretty sure you only have one sensor on the 2.4 liter engine.

The temp sensor looks like this:

Should be easy to change with a deep well socket of the correct size.

The PCM is hanging on the firewall passenger side, a silver box with three large wiring harness connectors plugged into it. Easy to change out, but expensive. Hope the sensor is the only issue here.

 

[Jeep in Ethiopia]

I believe the connection you want to remove is here:

Pretty sure you only have one sensor on the 2.4 liter engine.

View attachment 170719

The temp sensor looks like this:

Should be easy to change with a deep well socket of the correct size.

View attachment 170720

The PCM is hanging on the firewall passenger side, a silver box with three large wiring harness connectors plugged into it. Easy to change out, but expensive. Hope the sensor is the only issue here.

That's super clear. Thank you so much!

For the sensor, is it disconnecting it (on the black end of that sensor) or unscrewing it? I assume it's the former option. I've never locked at this before. It's super late here so I can't really look at it until tomorrow. Otherwise, I'd just go outside and check it right now. My security guards would wonder what the heck I'm doing.

 

[Steel City 06]

That's super clear. Thank you so much!

For the sensor, is it disconnecting it (on the black end of that sensor) or unscrewing it? I assume it's the former option. I've never locked at this before. It's super late here so I can't really look at it until tomorrow. Otherwise, I'd just go outside and check it right now. My security guards would wonder what the heck I'm doing.

Disconnect the black connector for the test. If you unscrew it you will dump coolant onto the ground.
You will have to unscrew it to replace it, but you should be prepared to catch and refill the coolant. Chances are you’ll have to unplug it to unscrew it anyways

 

[mrblaine]

Ok, just a hunch here but I think this is what is going on. The temp sensor is sending data to the PCM, the PCM is controlling the gauge and the fan relay. Disconnect the wire to the temp sensor and tuck it away so it doesn't get sucked into the belts or anything. Disconnect your battery for a few minutes. Reconnect your battery, but leave the temp sensor disconnected and start the vehicle. See what happens. I think your temp sensor has failed. Could be a bad PCM also, but the sensor is cheap to replace. Start there.

Also make sure both fan relays are re-installed. It has two for high and low speed fan operation.

I had my helper peruse the diagram. He reports that if the dash gauge is working, the temp sender should also be working. If the relays fail closed, the fan will run with the key off. The power to the relays is direct from the battery with a circuit breaker on the ground side.

A bad sender would make the fans run full time and a check gauges light turn on due to the gauge being pegged one side or the other.

If the dash gauge is working, then the sender is likely good and the issue is between the sender output, PCM and its output to the relays.

If one unplugs the connector off of the sender, that should force the fans on full time with the key on as a default to prevent overheating in the event of a sender failure.

About the most we can decipher from the wiring diagram.