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Cooling Fan won't come on - I'm stumped for tonight.

Started by davexz, July 13, 2011, 11:17:36 PM

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davexz

OK - I have a vision (bike #2) where the fan won't come on.  I look at the schematic and I narrow it down to the thermoswitch.  Why? because when I pull the lead off and touch it to ground the relay clicks and the fan turns on.  I try 3 used ones and it still doesn't work.  I boil them in water like the manual says and it looks like they are bad.  I order a new one ($89 bucks) and try it and it still doesn't work.  I take one out of my other bike (bike #1) that I know worked a week or so ago and it still doesn't work in bike#2.  I stick the new thermoswitch in the bike#1 that used to work and now it doesn't work either.  I suppose I could put my thermoswitch back in bike#2 to see if it works again like it did but I'm low on energy right now and need to regroup.  So I have tried 5 different thermoswitches in bike#2 and no fan - I also have bike#1 with the new thermoswitch and no fan now - I lost ground.  I also swapped around the relay and no change.  I'm going nuts - on both bikes if I short the thermoswitch lead to ground the fans come on - what the heck else could it be besides the thermoswitch.  When I short to ground I short it to the coolant pipe the switch is in so I know that is a good ground because the fan always comes on. Heck I even jumpered the thermoswitch housing to ground to make sure and no difference.  I have a full radiator so the thing is getting hot.  Both rubber coolant lines are getting hot so I know the thermostat is working and my temp gauges shows high temp.  Are these thermoswitches super fragile?  The manual says that if you tap them you may need to get a new one?  Any ideas?

Re-Vision

Suspect that you have a bad Ground connection from Thermostatic Switch Connector (3Pin) and Grounding Ring near Front Coil on left side of frame. Trace this Ground Connector Ring back 10 inches into wiring harness and you will find a crimp connector (Likely a poor connection here but also check connector for corrosion) tying the Thermostatic Switch Connector to the Ground Connector Ring.If you don't want to tear into the harness, try adding a new wire from Thermostatic Switch Connector (Black Wire) to a good ground connection on the frame.     BDC

Rikugun

That's some good info - I was unaware of that crimp connector in the harness. I may add a supplemental ground to mine just as a preemptive measure.

Davexz, it sounds like it's been driving you nuts, sorry to hear that!  :(  I've had problems like that and sometimes just looking at it the next day with fresh eyes helps.

That's curious how three used ones all tested bad. Also how the new one failed to work in bike #1! Let that be a lessen to you: Never mess with a functioning system! Could it be the ground was marginal on that bike too and disturbing it tipped the balance in favor of the electron demons!?

Hopefully between checking the multi plug connector and running an additional ground you'll be good to go.
It is far better to grasp the universe as it really is then to persist in delusion, however satisfying or reassuring.  Carl Sagan

davexz

Thanks for the help.  Yea sometimes it best to give up and try another day.  I'll look into that ground because I got something wrong.  Is that a ground for the fan?  What has got me is when I pull off the thermoswitch lead and touch to ground the relay flips and the fan comes on.  Thats why I keep looking at the thermoswitch.  How does the ground in the 3 wire connector play into this?  Is it the ground for the relay or the fan? 

Re-Vision

I formulated my reply about a possible ground problem on the basis of an intermittent ground problem or a possible short of the Thermoswitch housing to the bike frame. It appears that you have troubleshot correctly in as far as the ground is concerned. The likelihood of having five bad Thermoswitches is slim, perhaps you could check the resistance of one with an Ohmmeter when its hot.
The ground for the Thermoswitch housing is routed through the three wire connector to the crimped connections mentioned previously and should energize the relay whenever the Thermoswitch is closed. The ground wire from the cooling fan motor goes through a two wire connector and ties to the same crimped connections as the Thermoswitch.     BDC

davexz

I've got a good ground to the coolant housing, I even ran a separate jumper to ground and no difference.  But I hear ya - the chance of all the thermoswitches being bad sure did seem wrong so I went back out last night and retested 4 of them (5th still in bike) with a little better set up and all were bad.  They stayed open the whole time up to about 107 C.  The manual says they are suppose to close about 95C and above.  I should just put a manual switch in there but now I have a quest to solve this thing.  It has to be the thermoswitch - stay tuned I'll let you know when I get a new one.  I'm going to test it first before I put it in the bike.

Re-Vision

Hope you don't spend any more money on a Thermoswitch, I can send you one still in the housing that will likely be good.     BDC

Lucky

stoopid question:  your not wraping the switch in thread tape or using pipe dope are you?...
1982/3 XZ550 Touring Vison, Gold on Black

Re-Vision

I thought about that but figured surely it would cut through and make contact.    BDC

Lucky

1982/3 XZ550 Touring Vison, Gold on Black

jasonm.

hey...here's the fix.The switch completes the ground to the fan...SO, run a direct ground to one or  both terminals of the switch... If the fan works instantly. Which will happen even w/ignition OFF. Then...your tape is the issue .  Now you can fix your mistake w/o removing the switch by finding out which of the 2 terminals is INPUT ground. And run a jumper from that wire to the frame. THe input will be the wire that does NOT trigger the fan instantly when you run a ground to it.  Remember the fan circuit is ALWAYS live.
looks aren't important, if she lets you play by your rules