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2003 CB919
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Discussion Starter · #1 ·
This post is just to see if anyone else can offer a better solution or a better way to do this. And maybe to just leave the info out there in case I'm not the only one who thinks this may be beneficial.

When I bought my 919 it had a dead cooling fan relay, among other issues, and since I'm a broke ass and Honda want to charge $75 for a relay that should cost $20, I decided to grab a marine switch I had handy, wire it up and just ziptie it to the handlebar which has worked okay since then except for the couple times I've left it running and drained my battery, (woops, glad the cb is pretty easy to clutch-start)

I decided I'll just replace the original relay with a generic 4pin relay, so I checked the ECU actually triggers it and noticed that the trigger waits until the motor is very hot, hotter than I think is reasonable (just over 3/4 of the gauge when it stays in the bottom 1/4 of the gauge while I'm moving). So while looking at my options I figured the best thing would be to use a 5pin relay and add a trigger button and timer for about 60 seconds so I can trigger the fan and not have to worry about draining the battery while allowing the ECU to trigger it as usual in the event that I don't notice it getting hot for some reason.

This is the timer I'm planning on using here. I was hoping to find a time delay automotive relay but they are very expensive and these are cheap, so I'll just find some kind of waterproof enclosure to keep this in under the seat. I also added an extra relay to limit the current flowing through the timer itself.

I'll add a picture of a quick wiring diagram I put together while I was thinking about this earlier.

Any thoughts? Is this a stupid idea?

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McTavish
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6,570 Posts
I'm not an electrical guy but see how you've conceived the necessary On/Off and Run Time controls.
The logic is sound in my mind.

Have you looked at pages 19-14 &-15 of the official factory service manual?
Not, suggest you do re the ECT (Engine Coolant Temp') Sensor.
Your fan start point is high IF the temp gauge is correct.
Normally, the fan comes on at about mid sweep of the needle.
Maybe the ECT is duff and sending faulty temp indication to the ECU.
Short story, the accuracy of the ECT needs to be proofed in order to eliminate it as being a possible primary or co-causal re what might be an abnormally fan start temp.
IF the ECT is proved as being within specs, then the temp gauge becomes suspect.
Ultimately, you are working on two things, Fan Controls and ECT Sensor accuracy.
While the ECT does feed to the ECU, which is what actually signals the fan, I am doubtful of an ECU failure in that respect alone.
Hopefully this is of some help.
 

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2003 CB919
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5 Posts
Discussion Starter · #3 ·
I can't believe I didn't think to consult the service manual, I'm an idiot sometimes.

It seems you were correct, following the instructions in the manual, it shows a voltage (5v) between the sensor pin and ground so that means the gauge itself is faulty.

The service manual is unclear on whether the temp gauge can be accessed once the cluster is out so I'm debating if it's worth pulling the cluster to see if I can do anything with it, I suspect I will have to replace the whole cluster.

Anyone have experience pulling the cluster that may be able to suggest a cheaper fix for that? I've been looking for 919s at local wreckers because I was looking for the forks and shock from the post '04 model and so far I've had no luck. Now I guess I need to try find a pre '04 gauge cluster too now.
 

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Left of Centre
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Anyone have experience pulling the cluster ....
Yes, I bought a new shell for my cluster when a garage topple-over smashed the mounts off the orig one. I just swapped the whole cluster without pulling it apart, item by item, so I don't know what would be possible - perhaps a parts diagram would show how many components they break down into, if at all.

Also, this - not an exact match but you might be able to get close...
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2003 CB919
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Discussion Starter · #5 ·
Yes, I bought a new shell for my cluster when a garage topple-over smashed the mounts off the orig one. I just swapped the whole cluster without pulling it apart, item by item, so I don't know what would be possible - perhaps a parts diagram would show how many components they break down into, if at all.

Also, this - not an exact match but you might be able to get close...
I think I'll pull the cluster when I find time (probably not this weekend) and see what it looks like, the ride to work is straight down the motorway so I don't have to worry about overheating on my commute. I do still have the switch installed, so I can just run the fan anytime I'm not moving.

If I have to swap out the whole thing I might consider going with an aftermarket cluster like a trailtech or something although I am trying to not spend any unnecessary money at the moment.
 
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