Radiator Fan not switching on...leading to overheating

Hi. I'm new to the forum and seeking some pointers. My 2004 FJR overheated in heavy traffic because theradiator fan didn't switch in when it should have. If I apply power direct to the fan it works, so I'm thinking it's either the fan motor relay or temperature sensor (if it has one seperate to the one that drives the temp dispay?? - which is working fine).

My problem - I can't find the location of the fan motor relay or temperature sensor and trying to follow te wiring back through the loom is doing my head in!!

Any pointers very much appreciated - thanks in advance.

amberdaz

Amber,

Here is a post for the Relay:

https://www.fjrforum.com/forum//index.php?s...mp;#entry559195

or it could be the Temp Sensor:

https://www.fjrforum.com/forum/lofiversion/...php/t17894.html

or your Main Harness may be Corroded and not allowing the Relay to trip, here is a way to do this:

https://www.fjrforum.com/forum//index.php?s...st&p=268059

or if you are low on Water or have an Air Bubble in the System, the Sensor/Relay may not trip. In this case you should Burb the System (get the Air Out) and this may solve your problem. (Do this first)

Go Luck on your fix....

amberdaz said:

Hi. I'm new to the forum and seeking some pointers. My 2004 FJR overheated in heavy traffic because theradiator fan didn't switch in when it should have. If I apply power direct to the fan it works, so I'm thinking it's either the fan motor relay or temperature sensor (if it has one seperate to the one that drives the temp dispay?? - which is working fine).
My problem - I can't find the location of the fan motor relay or temperature sensor and trying to follow te wiring back through the loom is doing my head in!!

Any pointers very much appreciated - thanks in advance.

amberdaz

Click to expand...

I had that same problem happen at the begging of April on the way to Arkansas to attend the 2nd Annual TwistyButt 500 ride.

I was about 800 miles into the trip up to AR, somewhere in Alabama stuck in traffic on I-65 with the ambient temp around 85F. As soon as I was able to get off the Interstate i pulled over into the closest gas station and started troubleshooting the problem. I checked the fuses which where OK. Then I went into the Diag screen and manually activated the fans, I could hear the fan rely click but the fans didn't run. I ended up jerry-rigging a the old On/Off SPST ignition switch i used to carry around before the ignition recall (I have the GenII) and some spare emergency wiring I keep on hand. I pulled off the two lower fairings, unplugged the fans and spliced into the fan wiring on the fan side. This worked OK for the rest of the trip to AR, the AAD500 and the trip home. I've ordered a replacement relay which should arrive early next week, so I'll post up my results.

I believe the temp sensor is located on the RHS end of the coolant pipe sitting on top of the rocker cover, it's got a green color connector in all Gen FJRs.

From my troubleshooting, I don't think the temp sensor is faulty because the DIAG should activate the fans directly, bypassing the temp sensor, and since the fans themselves work.

I suspect the relay mechanicals are simply worn out, which means contacts don't make a solid enough connection when engaged, this leads to more "contact burn" which helps wear away and oxidize the contacts...

Thanks Silver - really useful links to previous posts (which my searching failed to find - but i'll get better, promise!!).

As it happens I spent the afternoon tracing the wiring and finally found the radiator fan relay - it's the centre one mounted directly behind the dash clocks. Had relay out and tested it - seems to be working fine! And the wiring to the switch side of the relay connector are also fine. So by deduction that only leaves the wiring from the ECU to the relay to check. (Job for another day 'cos I stuck the end of my thumb and was bleeding like a pig so gave up for the day :angry:

I do have a couple more questions...

1) The bike's not normally running hot - only when I gt stuck in bad traffic for about 20mins. Am I safe to assume that means I have no air bubble in the cooling system?

2) The temperature readout on the digital display is working fine (it is - but the fan's not kicking in at 4 bars, or even 5), does that mean that there's no point me checking out the temp sensor??

(I'm assuming that the digital display temp readout and the switching of the radiator fan relay are all triggered off the same thing)

Thanks again for the help - this forum is awesome!

amberdaz

Amber,

You may want to Burp the System of Air Pockets and make sure you have the proper level of fluids.

There are situations where if there is Air present in the System, I may not trigger the /Temp Sensor/Relay even though you see the Bars on the Dask.

Then go from there. I would take off the Right Front Panel, take off the Radiator Cap and warm it up to 4 Bars or so and see where the Coolant is and if you may also have a challenged Radiator Cap.

(Remember to use the 50/50 mix or Antifreeze with Distilled Water- you don't need hard water left overs in your bike's coolant system)

Good Luck on this....

amberdaz said:

Thanks Silver - really useful links to previous posts (which my searching failed to find - but i'll get better, promise!!).
As it happens I spent the afternoon tracing the wiring and finally found the radiator fan relay - it's the centre one mounted directly behind the dash clocks. Had relay out and tested it - seems to be working fine! And the wiring to the switch side of the relay connector are also fine. So by deduction that only leaves the wiring from the ECU to the relay to check. (Job for another day 'cos I stuck the end of my thumb and was bleeding like a pig so gave up for the day :angry:

I do have a couple more questions...

1) The bike's not normally running hot - only when I gt stuck in bad traffic for about 20mins. Am I safe to assume that means I have no air bubble in the cooling system?

2) The temperature readout on the digital display is working fine (it is - but the fan's not kicking in at 4 bars, or even 5), does that mean that there's no point me checking out the temp sensor??

(I'm assuming that the digital display temp readout and the switching of the radiator fan relay are all triggered off the same thing)

Thanks again for the help - this forum is awesome!

amberdaz

Click to expand...

I still think, and hope it's just a worn relay, at least in my case because it would avoid further dicking around troubleshooting. Now the other fun part, trying to figure out which relay to order :dribble: On the GenII fiche there is no specific description of which relay is which, so I imagine the same applies to the GenI too. Even calling up the parts guys didn't help since they don't seen to have any more info than what we the retail people get to see. The best advise they could give me was "try to match the approximate position of the relay on the schematics and get that one". From examining the two side-by-side mounted relays in that area on the GenII the Headlight and the Fan relays appear to be the same so should be interchangeable if you ordered the wrong one...

Okay, think I've finally found the problem, though if someone with good electricals knowledge could confirm my suspicion that would be ace...

Followed Silver's advice, burb'd the system and checked the connectors for any corrosion - no problems found and I double checked by simply checking the connectivity of all the wires in the radiator fan circuit from source to destination with the trusty test meter - all good.

So this leaves me with a fully connected circuit, a fan that's operating if I put 12V across it and a relay that's switching if I put 12V across it's solenoid...

The green/yllow wire out of the ECU is dropping to earth when the bike hits 4 bars on the temp display, which is tripping the relay - perfect, but nothing from the fan... now I'm getting annoyed :angry2:

Back to basics...

• I break the connector just before the fan - apply 12V across the fan side and the fan operates, all good with the fan.
• Put my volt meter across the other side of the connector (coming from the relay) and when I trigger the relay (manually by shorting the green/yellow wire to earth to simulate what the ECU would do) I get 12V registering on the voltmeter (14V if I have the bike running) - so the relay appears to be connecting the power through okay! So why the hell aint it working???? Now I'm getting really annoyed :angry:

So I suspect that there's something wrong with the relay when it's under load i.e. it switches okay, but if you try to put any current through it then it aint playin'

I tested my theory by connecting an inspection lamp with a 25W bulb in it across the connector from the relay that's registering 12V on my voltmeter - with this relatively small load on it, I now get no voltage registering and the lamp doesn't operate diconnect the lamp and my voltmeter registers 12V again.

I also tried reconnecting this connector block and simply shorting across the switch terminals on the relay - and the fan operated perfectly.

Question: Am I correct in my suspicion that this means the relay is the culprit after all, and even though it switches and shows a voltage, that it's not capable of passing any currect through if you connect anything to the other side of it to put it under load???

[Even though I just wasted another 3hours of my life checking out the coolant and all that wiring I'm really hoping someone confirms my theory then I can just throw in a new relay and put all that bodywork back on and go for a blast ]

JamesK said:

I still think, and hope it's just a worn relay, at least in my case because it would avoid further dicking around troubleshooting. Now the other fun part, trying to figure out which relay to order :dribble: On the GenII fiche there is no specific description of which relay is which, so I imagine the same applies to the GenI too. Even calling up the parts guys didn't help since they don't seen to have any more info than what we the retail people get to see. The best advise they could give me was "try to match the approximate position of the relay on the schematics and get that one". From examining the two side-by-side mounted relays in that area on the GenII the Headlight and the Fan relays appear to be the same so should be interchangeable if you ordered the wrong one...

Click to expand...

Well as a reference point to follow up on my diagnosis of my own similar (identical) problem. Today I finally received the new Fan relay a simple plug & play swap in fixed the fan problem. So your further testing simply verified my original troubleshooting conclusion that the relay is toast.

Just order a new rely and all will be well again.

The high/low beam headlight relay is identical to the radiator fan relay. So you can try that relay in the fan circuit to see if the fan runs as expected.

Constant Mesh said:

The high/low beam headlight relay is identical to the radiator fan relay. So you can try that relay in the fan circuit to see if the fan runs as expected.

Click to expand...

Yep, they are, just be real careful unplugging them, since those little lock tabs are very fragile. Having experienced two OEM relay failures on my 07 with 88k miles on it, the Headlight On/Off relay a couple of months ago, and now the Fan relay, I preemptively also replaced the Headlight HI/LO relay. Btw, these two relays are also the same as what I think is the ABS related relay located by the ABS controller box.

Is there a 'most common' error for when the fan doesn't work?

What's recommended to check first?

Hopefully it's what's easiest!

[Note this thread was 2 years old. Atta'boy for searching!]

Fast 'n easy, go to the diAG screen and use actuator code 51 to turn on the fan relay. If you hear the relay click the problem is most likely the fan. If the relay does not click the problem is most likely the relay. You can unplug the fan connector and jump 12 volts to the connector pins and see if the fan turns. Ground the fan's black wire and put 12 volts to the blue wire.

As previously mentioned in this thread the headlight HIGH/LOW relay is the same as the Radiator Fan relay and you can swap the two.

Detailed troubleshooting:

The coil of the relay gets power from the ignition fuse Red/White wire, and gets ground from the ECU Green/Yellow wire. The relay contact gets power from the Radiator Fan fuse, Brown/Black wire and goes to the fan connector on the Blue wire. With the relay plugged in clip your volt meter to the Red and Green wires, then use diAG to turn on the fan -- read 12 volts upon actuation. This verifies that the coil of the relay is being turned on by the ECU.

If this passes clip the black meter lead to a good ground and clip the red meter lead to the Blue wire and actuate the relay again -- read 12 volts upon actuation. This verifies that the relay contacts are closing.

If this passes the problem is the fan.

ionbeam said:

Fast 'n easy, go to the diAG screen and use actuator code 51 to turn on the fan relay. If you hear the relay click the problem is most likely the fan. If the relay does not click the problem is most likely the relay.

Click to expand...

Actually, reading back through the earlier posts in this thread, both people had the relay clicking and no fan running, and in each case the problem was still a faulty relay, one that the load contacts had eroded on enough to not be able to run the fan. In the one case measuring the relay output unloaded showed the proper 12V on the meter, but loading it the voltage was dropped on the contacts.

So in retrospect, you might say that the most likely problem is always the relay, whether it clicks or not.

Fred W said:

So in retrospect, you might say that the most likely problem is always the relay, whether it clicks or not.

Click to expand...

Note that in the detailed troubleshooting I say to leave the relay plugged in when checking for voltage on the Blue wire. This will detect failed contacts.

There have been instances of failed fans so I covered that. I did try to put out some troubleshooting that could be done without having to take off all the plastic to access the relays. Once ALL the plastic is off it is simple to swap with the headlight HI/LO relay.

The problem is likely to be the relay but it is worth verifying what you can before stripping off the plastic.

Someday....I want to attend a one day FJR electrical troubleshooting seminar hosted by Fred and Alan. I would hope that I would learn something...I KNOW I would be entertained. :lol:

Learn something? Those two would be arguing about which way current flows the whole time....

odot said:

Learn something? Those two would be arguing about which way current flows the whole time....

Click to expand...

downhill. current is like water, downhill

odot said:

Learn something? Those two would be arguing about which way current flows the whole time....

Click to expand...

But...it WOULD be an intelligent argument!

odot said:

Learn something? Those two would be arguing about which way current flows the whole time....

Click to expand...

Ya, those sneaky electrons. While everyone is distracted by the red meter lead the electrons are industriously flowing from the negative pole to the positive pole in the reverse direction from which the meter reads :blink: