ST1100 overheating issue

[moosulkwanman]

If the fans did not go on, it's a fan problem. you replaced the temp sender but not the fan switch at the bottom of the radiator. Also make sure the radiator is grounded.

Could be a wire problem, to the fan, had this problem myself, wire had rubbed a bare spot and was shorting out, problem was finding it, and getting to it as it was in Tight spot under the seat, under the gas tank cover deep in there, solution was covering , surrounding it with non conductive sealant silicone, Honda mechanic couldn’t figure it out but that’s what it was, a bare wire that was damn near impossible to get to

 

[moosulkwanman]

I’m back!

I managed to get a few hours with the bike today, so I carried out:

check the rubber hose from the thermostat to the overflow and there was a few small cracks at the top, so snipped about an inch from it and secured it with the new clip.

I then topped up the system with antifreeze, made sure the level was correct in the overflow as well.

put the new Honda cap on and went for a ride.

came back and let the bike idle for ages until it was right up in the red zone - no leaks of anything and the fan was on, but turning slowly… not like a fullblast as you would expect…

it seemed to bring the temperature down slightly… but certainly wasn’t working like I would expect or as fast as it does when I jump it.

I’m in the office for the next few days, I’ll give it a run and see how it goes…

had similar problem before, at speed the engine will cool down, standing and running at a red light or whatever, fan wouldn’t come on and the engine would overheat, only thing wrong was a bare spot on a wire to the fan was grounding out/shorting out. This was several years ago, but if my memory is correct, the wire was deep in a tight spot under the gas tank cover and was a real bitch to find and repair, once I found it I just covered the bad spot with nonconductive sealant silicone stuff, because it was so difficult to get to and pulling the wire and rewiring the fan would have been a real pain, design flaw was my opinion, good luck

 

[Larry Fine]

When I jump the fan/ground it it comes on full blast like i would expect it to. - very fast, full power etc.

Then there is a resistance in the switch, its wiring, or its body being well grounded.

 

[the cueball]

So the fan is still not coming on "properly"..

The bike is fine in the morning when I have a bit faster traffic and the ambient temp is cooler... but coming home in a bit warmer temps and riding a lot slower/stuck at lights.. the bike temp just keeps rising and rising, nothing leaking or overflowing so that's good (I guess)..

I've started to shut it down for now... but I guess I'm now going to need to take all the tupperware off and search for a bare wire somewhere!

I really don't want to give up on the bike.. but it's getting harder and harder to keep going at the moment...

 

[Pop-Pop]

So the fan is still not coming on "properly"..

The bike is fine in the morning when I have a bit faster traffic and the ambient temp is cooler... but coming home in a bit warmer temps and riding a lot slower/stuck at lights.. the bike temp just keeps rising and rising, nothing leaking or overflowing so that's good (I guess)..

I've started to shut it down for now... but I guess I'm now going to need to take all the tupperware off and search for a bare wire somewhere!

I really don't want to give up on the bike.. but it's getting harder and harder to keep going at the moment...

My fan rarely comes on, even in stop and go downtown boston traffic. But, my temp gauge rarely gets higher than 3/4 hot. Ive checked the fan wire connect and all seems fine. My red has never red lined. I dont know if this helps you, and i wish you the best.

 

[dwalby]

I've started to shut it down for now... but I guess I'm now going to need to take all the tupperware off and search for a bare wire somewhere!

When you "jump" the fan, are you bypassing the thermal switch to ground? I'm assuming that's what you're doing, if not please clarify.

That would suggest that the fan motor is OK, and when you jump it you provide a better path to ground than what the thermal switch is able to provide. If that's the case then you want to look at a connector at the top of the fan housing, which provides the ground path for the thermal switch. You probably have corrosion in that connector, or the ground wire connection to the radiator that goes into that connector. Its been a long time since I looked at it, so I can't recall exactly how the ground wire gets connected to the radiator, but it will be obvious when you look at it. Make sure the connector is clean, and the wire to the radiator is clean and then measure the resistance from that path to battery negative, it should be only a few tenths of an ohm.

 

[the cueball]

Yes, by jump I mean I'm removing the spade connector on the switch and using a "jumper wire" to ground it directly to the frame.. the fan comes on...

Thanks for the help, I'll add looking at that wire to my list!

 

[ST1100Y]

hmm...
UK...
road salt...
I'd recheck the fuse box...
I'd also see if the ground wire of the fan motor bracket is rotten...

 

[dwalby]

just to avoid any confusion, the radiator image Martin posted was upside down, here's the usual orientation. Unfortunately if the wire connection to the radiator is corroded, as shown in this image you'll have to pull the radiator to clean it up, I don't think you can access it without removing it. For troubleshooting purposes though, you can access the connector easily enough, and do a resistance check from the base of the thermo switch to the pin in the connector for the wire that attaches to the radiator body. The service manual claims its a green wire, but it looks like in the picture they're both black. Maybe its a green wire with a black sheath over it, and if so, see if you can pull back the sheath to identify the green wire. If you find high resistance in that path, then that's where the problem lies and will need to be cleaned up. Also check the path from the other side of that connector (that should be a green wire) to battery negative to verify the rest of the path to ground looks good.

 

[Larry Fine]

Is it possible you have a gauge sender installed instead of a fan switch? I don't know whether they are interchangeable.

A good troubleshooting method is measuring for what is called "fall-of-potential" voltages where there should be none.

This is done with the load on and drawing current. Start with a voltmeter set to 12v dc or greater, and lower it as you go.

For example there should be almost no voltage (> 1-2v) between the battery + terminal and the + terminal of the motor.

Likewise, there should be almost no voltage between the battery - terminal (or other ground) and the motor - terminal.

With the fan motor turning that slowly, several volts are being dropped across a wire or connection that shouldn't be.

 

[Ron]

Is it possible you have a gauge sender installed instead of a fan switch? I don't know whether they are interchangeable.

I don't know what he has installed.

The 2 are not interchangeable as far as functioning correctly.

 

[Larry Fine]

I don't know what he has installed.

The 2 are not interchangeable as far as functioning correctly.

I know; that was my point.

I meant that I don't know if they're physically interchangeable; whether ether will fit where the other goes.

 

[the cueball]

Well good news, it’s fixed itself… well…..sort of.

the temp gauge on the dashboard failed on the way home, so no reading at all….

I turned the bike off at the lights as I do and when I turned it on the gauge worked again.

had a few flashes of the fuel warning light for some reason too (half tank of fuel in the bike)

so clearly something going on and it’s not happy!

<sigh>

 

[ST1100Y]

hmm...
UK...
road salt...
Gremlins...

methinks you've some wiring issues...

 

[Josh_ST]

I'd be checking my grounding points for sure!

 

[kiltman]

Well good news, it’s fixed itself… well…..sort of.

the temp gauge on the dashboard failed on the way home, so no reading at all….

I turned the bike off at the lights as I do and when I turned it on the gauge worked again.

had a few flashes of the fuel warning light for some reason too (half tank of fuel in the bike)

so clearly something going on and it’s not happy!

<sigh>

There is a main ground wire from the loom that attaches to a bolt either at the folding grab handle on the left side or the bolt that holds the pannier rail on the left side.
This ground can cause false readings on the temp gauge. Took me some time to find the cause for my temp gauge not to read properly.
Another source for your electrical gremlins is the red wire to the main relay. Check that connector out as well. This is located on the left side of the bike just above the riders footpeg. it has a rubber boot covering a red connector. (there's a fuse holder on that boot with a green 30amp spare fuse in it) Take apart that connector and inspect it for melting. replace if necessary/ A temporary fix for that connector is to just remove the spade connectors from the housing and plug them directly into the relay. You may have to replace the spade connector on the red wire. NOTE where the wires aree in relation to the connector and how they are matched up to the relay. it's easy to burn out the clutch diode, and your neutral light will remain on in that case.

 

[the cueball]

Still not had a chance to look at this.. but this morning the temp gauge wasn't working at all.

I used the horn.. then it died.

The Side Stand and Neutral lights on the dash aren't working.

Feels like I'm heading towards a total failure at the moment..

 

[Slydynbye]

Still not had a chance to look at this.. but this morning the temp gauge wasn't working at all.

I used the horn.. then it died.

The Side Stand and Neutral lights on the dash aren't working.

Feels like I'm heading towards a total failure at the moment..

Don't worry you'll get an ample chance to look at it after you coast to a stop somewhere on the road

 

[kiltman]

Still not had a chance to look at this.. but this morning the temp gauge wasn't working at all.

I used the horn.. then it died.

The Side Stand and Neutral lights on the dash aren't working.

Feels like I'm heading towards a total failure at the moment..

Intermittent electrical issues are tough to find. start with the obvious, like insuring the battery terminals are tight (even if you've just checked do it again), check that ground in the loom like I mentioned before. Check the main lead going to the fuse box. Make sure the main relay connector is clean and tight. Check that the ground from the alternator is secure. Just above the green connector for the side stand switch is a main red wire, I've seen the insulation come off it due to vibration and rubbing on the frame. All these are on the left side of the bike in the battery area.
good luck

 

[red one]

Just a thought but did you buy your bike used? Has previous owner added any accessories? Was it done correctly? If yes is the answer you need to dig into the wiring and check their work. Problem could be there. ST1100's don't have failures like that so its fairly uncommon.