Radiator Cooling Fan Not Activating at Temp

[QuadX]

Yesterday I was working on syncing the throttle bodies on my 2005 FJR. Syncing requires a lot of starting and stoping of the engine and a lot of idle run time. For first few runs the radiator fan would kick in at 4 bars, but later in the process the fan no longer would kick in. As soon as the temp got to 6 bars I would turn off the engine and let it cool.

Today I did a diag check of the radiator fan. I would hear a click as the engine light would turn on and off to actuate the fan, but he fan would not turn on. I checked the fuse and it is fine. I assume it is not the thermostat sensor, because if it was then the DIAG would still be able to trigger then fan.

So, my guess is either the Relay or the Fan. (let me know if I'm missing something)

What is the best/easiest way to test the fan motor?

How hard is it to test the relay?

Any other advice is always welcomed!

 

[Bustanut joker]

Quick and painless would be to disconnect the fan leads and check for voltage there..

 

[Geezer]

As Bust said, check for voltage to the fan when it is trying to run.

Spin the fan by hand to verify that there are no binds.

Apply 12V directly to the fan motor and see what happens.

 

[ionbeam]

The good news is that the fan relay clicks.

The problem showed up after many fan cycles in a row causing the wires, relay and fan to heat up, and heat causes problems to express themselves. There is a chance that once things cool down the problem symptoms will have gone away, but the underlying problem will still be there and it needs to be fixed before warm weather returns.

I would recommend that you check for voltage at the fan connector by back-probing the connector while the fan is plugged in because this has the wires under full electrical load. If you have 12 volts at the fan connector the problem is the fan. If you don't have 12 volts read on.

It is becoming more common to see this kind of fan failure in the older Gen I. The problem is often turning out to be a bad wire and sometimes a bad relay.

The fan relay is the same as the headlight relay and they can be swapped to troubleshoot the issue. Once you finally can get to them.

There have been several failures that I know of where the power wire to the fan was burned inside the insulation, from the outside the wire looks OK, but when the fan tries to draw full current the wire is not up to the job and voltage will not pass beyond the internal damage. So far the problem has been the Brown/Black wire between the fuse and the fan relay. Depending on your electrical skills and electrical tester you can either troubleshoot the problem or use a piece of wire to jump 12 volts to the relay and see if the fan runs. If it does, you need to trace the Br/B wire back to the fuse looking for the internal damage. What has generally been found is internal wire damage within a few inches of the relay socket.

If I have time I may be back to add to this post.

 

[Fred W]

There are two fuses in the fan circuit: One for the actuation (coil) side of the relay, 10A , called the ignition fuse (ignition switched 12V), the other is 15A for the fan power to the switching side of the relay (constant 12V). The fact that the relay clicks when you run the diag says the former is OK, but the latter is still suspect.

Otherwise, the relay contacts are suspect and the fan motor itself. I would imagine that the more likely is the relay contacts have arced and burned up. Much more likely than the fan motor.

 

[Redfish Hunter]

Bust, Fred W, Geezer and Ionbeam are all absolutely on the money here. I would have made those same recommendations myself though probably not as well as Fred and Ion expressed it. Bust gets points for simple, brief and to the point.

Like Fred and Ion, I believe that a voltage test without a load on the circuit may be useless. Scorched contacts in a relay or a heat damaged wire may allow a good voltage reading but not allow enough current flow to maintain that reading under electrical load. I have been "burned" more than once by a relay with scorched contacts in just this way.

 

[JamesK]

I experienced a failed relay on my 2007 at around 60k miles, I was exiled in South FL for most of those miles so the fans had to work extra hard. The relay itself was working (clicking) but the contacts had burned enough to make a bad connection when activated. If this is your problem (given the age of the bike), you cold test it by tapping the relay case with the handle of a screw driver or something to see if the fans come on (when at temp), this is how I confirmed my relay problem.

Or as Ionbeam mentioned if you have easy access to the both the Headlight relay and the Fan relay simply swap them over to test. From memory this relay is only around $20 so probably does not hurt buying a new one to have as a spare.

 

[Bustanut joker]

Bust, Fred W, Geezer and Ionbeam are all absolutely on the money here. I would have made those same recommendations myself though probably not as well as Fred and Ion expressed it. Bust gets points for simple, brief and to the point.

Geezer and I are the kind of guys who don't go to a lot of trouble just to cause ourselves trouble..

Those other two jerki bois have too much time and smarts to be as smart as me an Greg.

 

[ionbeam]

Geezer and I are the kind of guys who don't go to a lot of trouble just to cause ourselves trouble..

There is 'looking for the problem' and effective troubleshooting. The difference is several hours of wasted time and wasted $$$ replacing good parts. Put a little effort up front for good troubleshooting and there will be a lot more time and money left for drinking later

 

[dcarver]

https://candybuttorg.ipage.com/cba/node/175

For pix of disassembled relay.

 

[QuadX]

Thanks for all the help! The problem has been found and fixed. One of the wires in the harness had corroded. A little soldering did the trick!

 

[gumba]

If you're getting your engine hot enough to burn down your cooling system, you're not getting a very good TBS.

 

[ionbeam]

If you're getting your engine hot enough to burn down your cooling system, you're not getting a very good TBS.

Quad is drawing enough fan current over a long enough time period to compromise a wire. This is strictly an electrical failure. It would be interesting to know if it was the Brown/Black wire and to know if the corrosion was right at a connector or relay socket.

 

[QuadX]

If you're getting your engine hot enough to burn down your cooling system, you're not getting a very good TBS.

:blinksmiley: Quad is drawing enough fan current over a long enough time period to compromise a wire. This is strictly an electrical failure. It would be interesting to know if it was the Brown/Black wire and to know if the corrosion was right at a connector or relay socket.

It was the brown and black wire and it was at the connector, not the relay.