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Discussion Starter · #1 ·
This should be titled "paging DEcosse" the T509 electrical master. I have a high mile '97 T509 that the cooling fan stopped running on. It has gotten pretty hot but not really overheated. The thing that is strange is that the MIL is not on and my service manual states that practically any problem in that circuit should trip the light.

Any ideas?

Thanks,
Wally
 

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Hi Wally - haven't seen you on here in a while.

A fault in the cooling circuit would not trigger an MIL light on your bike.

Do you know for sure that it is reaching temp that would kick in the fan? Coolant gauge is reading high?
(have you seen any difference in your cooling gauge indication in recent times?)
The control mechanism for turning on fan (via the ECM) comes from same temp sensor; but if indication is what it typically has been, then no reason to suspect that - at least as first order.
i.e. any problem with the sensor would also be seen in the gauge.

On your model, the ground return is permanently connected to battery -ve and the power is switched by a relay.
You can disconnect the plug from cooling fan and ensure that you have continuity to battery -ve. (or conversely, if you put meter on V-DC then put one test lead on the battery + and the other on that black wire in the fan connector plug and you should measure 12V.)
If you don't then you need to ifnd the cause of the missing ground return (is your ground block in good shape, latest revision, blue clock with the extra wire that goes to the battery -ve?)


The Cooling Fan Relay is the second from right side in the row of 4 (the one on its right, closest to frame is the turn signal relay)

Power for the relay coil is ignition power, while the control signal (low) for the relay coil, comes from the ECM when the temp sensor reaches the fan set-point (103 degC)

The relay switched power directly to the fan through the mormally closed contact; the common, power in, comes from the same source as the main power relay input to both coil & common, so unlucky to be that.

First thing would be to make sure the fan spins freely - very common to get small rocks jammed in the blades which stop it turning.

If you can take a wire connected to your battery plus and touch that into the blue/white wire of the fan connector plug, then fan should run. If it doesn't, and you affirmed that the ground wire connection is good, then you must have a bad fan.

Next, try swapping the relay out with something that will give you an instant indicator of whether relay is good or bad - the fuel pump relay & main power relay (in that order) are next to the cooling fan relay - so if you swap your cooling relay into either of those, you should get very affirmative feedback of its functionality when you try to start the bike. (Fuel pump is a good one as you can hear the pump run for a few seconds without even attempting to start)

Next, energize the relay to see if it closes & switches power: turn on ignition and take a wire from the battery -ve touched to the black/yellow wire of the cooling fan relay - fan should run.

That's pretty much everything so hopefully that can hone you in on the problem.

If your power circuit all checks out to be OK, then perhaps the sensor is not reflecting the true temperature.

Good Luck!!!
 

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Discussion Starter · #3 ·
thanks!

Thanks DEcosse, I had this feeeling you would know more and be more helpful than the manual!

I loaned the bike to a friend so I am going to try and get down to work on it over the weekend. Fortunately, the guy was considerate enough to shut it down when it started heating up.

We were on a 5 day trip when this happened (turned over 75K on it on the way home). The gage still appears to work without any abnormalities and I know for a fact it is getting close to boiling over due to the conditions we put it through and the bad smell of coolant. One thing that did happen on the way down to West Virginia is the bike plowed through 6-8 inches of standing water a couple times when we got caught in a deluge.

Thanks again for your help and I will keep you posted,
Wally
 
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