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overheat light on

3K views 19 replies 8 participants last post by  Ramie 
#1 ·
the red light came on after about an hour of riding. As i got off the highway, sat in a mild traffic, and the light turned on. I got off the road, turned the engine off. Few minutes later, start, and off I went, without any problems. After a while, I rode back, also problem free. No weird noises. The fan did not seem to go on. A week ago I rode in a heavy traffic for an hour, and definitely heard the fan coming on. As I rode fast, without the traffic on the way back, and in somewhat cold temps of close to 33F, I think I could have been getting away with "air cooling", but I'm wondering if there is something wrong with fan or thermostat - any way to check it? It was a bit too dark to really see what's the level in the coolant reservoir, will take a look tomorrow, as the daylight would be helpfull...
Oh, BTW, it is ACE 750...
 
#2 ·
Look at the engine side of the bottom of the radiator, there is a single wire connected to something that looks like a large bolt, it has a spade connector so you can just pull it off..

With the ignition switched on touch that spade connector to any bolt that connects to the frame (ground) if the fan is ok it will run..

A modification you might want to do for when you are stuck in traffic and the engine is getting hot:-

Fit a handlebar switch and run one wire to the spade connector wire (you can get a simple in line adaptor) and the other wire to ground or frame..Now with the switch off the fan will start as it normally does but you can bypass the thermal switch and switch the fan on anytime you want to.

John.
 
#19 ·
Look at the engine side of the bottom of the radiator, there is a single wire connected to something that looks like a large bolt, it has a spade connector so you can just pull it off..

With the ignition switched on touch that spade connector to any bolt that connects to the frame (ground) if the fan is ok it will run..

A modification you might want to do for when you are stuck in traffic and the engine is getting hot:-

Fit a handlebar switch and run one wire to the spade connector wire (you can get a simple in line adaptor) and the other wire to ground or frame..Now with the switch off the fan will start as it normally does but you can bypass the thermal switch and switch the fan on anytime you want to.

John.
What model? I have a 1993 shadow... Could I do that on this as well???
 
#7 ·
ok friends, luckily I found the immediate problem right away - the fuse(fan) was blown, indeed. Now, what caused it - I hope just old age, it seemed a bit oxidized... Coolant level is just right, could not really find those switches on the bottom of my radiator, though...
 
#8 · (Edited)
ok, aparently, the fan is not kicking in - i started the bike, let it idle for about 20 minutes - the light came on, but the fan did not kick in. Will check the fuse tomorrow, as it got too dark to see now...
Also, John - are you talking about the very bottom left on the radiator, where I see some black wire with a black rubber sleeve going into what looks like, rather a large "nut", or a bit above, midway - there are also wires with a white rectangular "connecting", or may be it is only a fastener kind of thing. Not being shure what to pull, I thought I'd rather ask first. Both are on the left side(from sitting on the bike point of view), 98 Ace750.
 
#9 ·
To test the fan you do not need the engine running just the ignition switched on...

That rather large nut is a thermistor it has a single wire connected to it with a push on spade shaped connector which just pulls off..if you touch that to ground the fan should run..

The thermistor changes it's resistance and opens a path to ground when it gets hot..having a lot of sludge in the bottom of the radiator can insulate the thermistor from the hot water and stop it from working..but the test I described bypasses the thermistor.

John.
 
#10 · (Edited)
Got it John , thank you, will do tomorrow. While i am there - maybe I should pull the thermostat as well, to check it's condition, can it just be unscrewed (the "nut")? Do I drain the radiator for that? I did some search on these questions, but so far did not find much info yet...
Edit: Just checked clymer's - they call it "fan switch", I'm sure John means to unplug there, but if anyone has a tip on the possible cleaning procedure of that unit - would be great to be equipped with some wisdom from fellas here...
 
#11 ·
Hi Harpo, The Thermistor that John refers to is a different thing altogether to the Thermostat. The Thermistor mearly monitors the temp of the water and operates the fan when required, as John says. The Thermostat is a valve that stops coolant circulating through the Radiator until the engine is up to normal temp. It would however pay you to check the Thermostat as this could be staying closed and not letting the coolant through and causing your overheating problem. You can remove the Thermostat and check it by placing it in hot water and watching to see if it opens correctly, but if there is any suspicion of over heating I would change it as a matter of course as they are not expensive. Check in your manual and it will tell you how to locate and remove the Thermostat. This is a good time to flush your system through and fill with fresh coolant. Good luck.
 
#12 ·
Great tip, and I will do that, but I have a reason to suspect the "thermistor", as it (bike) sat in water for a short while... The fan worked afterwards, but maybe corrosion occurred over time(about 2 weeks later) - or is it not a possibility at all, as it seems well protected by its sleeve, and not much is exposed to the outside water, and maybe I shouldn't bother getting to its "innards"?
 
#13 ·
Ok amigos, assuming the test of the fan works with a blown fuse(again, after yesterday's test it burnt out and I did not have the spare this time), with ignition "on" I unplugged that spade connector, and touching it to the frame - no fan movement. the connector looked nice and clean on both ends - switch in the radiator (thermister) end, and wire. So, I tried spinning the fan by hand, as I remember it would freely turn by hand - no way, it is not moving. Now, fan & it's motor is my suspect - correct?
 
#14 ·
Ok amigos, assuming the test of the fan works with a blown fuse(again, after yesterday's test it burnt out and I did not have the spare this time), with ignition "on" I unplugged that spade connector, and touching it to the frame - no fan movement. the connector looked nice and clean on both ends - switch in the radiator (thermister) end, and wire. So, I tried spinning the fan by hand, as I remember it would freely turn by hand - no way, it is not moving. Now, fan & it's motor is my suspect - correct?
Yes you need a new one..as it was under water I suspect mud and debris has found it's way to the bearing..you really need a new one but it is often possible to strip the fan and clean it with WD40 to make it work again.

John.
 
#18 ·
new fan is definitely in the cards. I will try to revive this one, but chances are it's seen its better days... I really want to thank all of you for the help - without it, even these seemingly simple tasks would be impossible for someone like me, without much of technical experience and knowledge. Equipped with your friendly support, I see how working on the bike can be enjoyable, gratifying experience. Especially when there is a warm place to do it in, and tools are at hand. (not my present situation, but I do see it ;)
 
#20 ·
Old post but yes you could but why would you want to. If your fan isn't coming on just fix the problem, bad sensor or bad fan.
 
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