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The Water Temp Warning light on my speedo does not test when the ignition is switched on. This is an '06 VN900. I removed the speedo assembly per the manual and tested the light with a 12 volt source. The bulb is fine, the fan runs and cycles when the engine gets hot, just no test, and presumably, no overheat warning is available. Anyone else had this problem?
 

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Check the sensor and connectors (unplug and reseat) to the sensor and ECU. The signal from the sensor goes through the ECU to the bulb.
Temp sensor resistance (kohm):
32F: 6.544
104F: 1.136 +/- 0.095
212F: 0.1553 +/- 0.0070
 

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Discussion Starter #3
Check the sensor and connectors (unplug and reseat) to the sensor and ECU. The signal from the sensor goes through the ECU to the bulb.
Temp sensor resistance (kohm):
32F: 6.544
104F: 1.136 +/- 0.095
212F: 0.1553 +/- 0.0070
Thanks! Time to pull the tank and flush the cooling system anyway!
 

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Any updates pacomutt? I'm having the exact same issue on my 06 900 Classic. I've already tried unplugging/plugging everything to no avail. But I don't think the sensor is the problem, as the bike does startup in a fast idle and comes out of the fast idle after a few seconds (it depends if I left it idling or if I just took off and if the bike was already warm, for example, I know that when I get out of work, it comes out of fast idle two blocks away from work). Therefore I think that the ECU is getting signal.

Right now I'm going to buy a multimeter... I've already disassembled the speedometer, thinking that maybe I would be able to test the oil or FI LED instead of the temp led, but that didn't work (connectors are different). I'm suspecting that the temp led is burnt, but won't know until I get the multimeter.
 

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Dang...

I've done the procedure on the service manual (16-69) and the led and speedo test OK (the led lits up).

So... It's either the temperature sensor, the ECU or a freaking cable somewhere in between the sensor, ECU or speedo... How FUN!
 

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Dang...

I've done the procedure on the service manual (16-69) and the led and speedo test OK (the led lits up).

So... It's either the temperature sensor, the ECU or a freaking cable somewhere in between the sensor, ECU or speedo... How FUN!
Tod, I've done everything you've done- pulled/reseated every connection, checked and confirmed LED on speedo works, checked ohms at temp sensor which read around 1500 ohms at about 90 degrees on the day I worked on it, so it reads where it should at start-up temperature. Like yours, the bike starts fine, fast idles and then settles to normal idle, runs well and fan comes on and cycles normally while riding.
I have not checked the thru-circuit wiring for continuity from the ECU to the sensor and back, but I will do so next time I have the tank off. I'll let you know, and please do likewise if you find the problem.
Funny, but the service manual points first to the LED in the speedo and wants you to replace the entire speedo unit even though the LED is in a plug-in socket that is plugged into a circuit board. How often do you think an LED light that only comes on during a bulb check on start-up would burn out???
 

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Take a look at your wiring diagram. Is there a water temperature "diode" in the circuit?

Post back.
Nope, nothing. I've been studying the wiring diagram so I can try to figure out what I need to check (I already went and purchased a multimeter, I already had one, but it's at my parent's place, that's why I tried everything that didn't involve a multimeter). On the temperature sensor, the orange wire goes straight to the ECU and the black/brown also goes to the ECU, but it is shared among a multitude of sensors (might be a common voltage/input?), then a yellow/white cable comes out of the ECU and goes to the speedo, nothing in between, and that one should be open during normal operation and grounded when the led is on.
 

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If the fan works OK, no FI light, LED checks out, then it is:

1. Bad connection/broken wire at ECU or meter. (Yellow/white wire)
2. Ecu not running LED test routine.
 

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Well, I'm done diagnosing my bike.

As I thought, there is no problem with the temperature sensor and the connection to the ECU, on both leads. This is also confirmed by the correct behaviour of the bike (going out of fast idle, etc.) To further prove that the ECU is able to tell if something is wrong with the temp sensor, if unplugged, the fan will automatically turn on, but at the same time the warning light didn't (obviously, the problem is that it won't turn on).

After the previous tests we concluded that the speedometer was working fine.

So it was either the ECU not sending a signal, or the signal getting lost in the way. Well, turns out that, at least on my bike, the yellow/white wire from the ECU to the speedometer is broken. So I either need to splice in a new cable in there or get a new wiring harness... :mad:
 

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Discussion Starter #11
Well, I'm done diagnosing my bike.

So it was either the ECU not sending a signal, or the signal getting lost in the way. Well, turns out that, at least on my bike, the yellow/white wire from the ECU to the speedometer is broken. So I either need to splice in a new cable in there or get a new wiring harness... :mad:
Tod, how do you know that it's this wire? Are you surmising, or did a continuity check reveal this?
 

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Take a look in the end of both connectors to make sure the pin has not folded over or pushed back and is tight in the connector.
 

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One other thing...could be a bad wire to pin crimp at either end.

A bad wire itself would be my last guess.
 

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If, by test, you mean the light comes on for a second or two when you turn the key on, mine doesn't test, either ('07 LT). Don't recall if it ever did. Do some of you out there have temp lights that test? My owner's manual only says that it comes on when coolant temp reaches 248. Doesn't say it comes on with the ignition.
 

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Tod, how do you know that it's this wire? Are you surmising, or did a continuity check reveal this?
I did a continuity test, first on the terminals, with were not bent, no continuity. Then tested the continuity between the terminal and the wire at the other side of the connector, before it is wrapped in tape (as close as I could to the tape), and it tested fine, so there is no problem on the connectors themselves. The last test was from the wire itself to the other end on the wire, again, no continuity.

I'm 100% positive on this, as I did every test at least twice. Trust me, I wasn't happy to find that a wire in the main wiring harness is broken, so I tried several times until I was convinced that there was no other possibility.

I wasn't eager to pinch the cable to do more tests, in fact, I'm already worried about the two places where I pinched it, so I'm going to put a new wire in there, cutting the existing cable from the points that were pinched, solder a new wire and cover it in heat shrink tubing. I know I could try unwrapping the wiring harness and continue testing, but that would be way too much work, I would rather buy a new wiring harness than doing that.
 

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If, by test, you mean the light comes on for a second or two when you turn the key on, mine doesn't test, either ('07 LT). Don't recall if it ever did. Do some of you out there have temp lights that test? My owner's manual only says that it comes on when coolant temp reaches 248. Doesn't say it comes on with the ignition.
Mine never did either, but I found on the service manual that the LED is supposed to turn on, p 2-39.


But wait a minute... I think I've screwed up, LOL! There are two Yellow/White wires on the ECU! (P 3-16 ECU pins 3 and 6) It seems that the one I was testing is not the correct one...

I will go test... again... will post back in about 1 hour (it won't take me more than 15 minutes, but I've gotta have a smoke first, I can't believe I spent that much time testing the wrong wire). At least I've got quite familiar with the bike, and this doesn't require removing the tank, I don't like to end up smelling like gas.
 

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Pffftt...

Yes, there was another yellow/white wire, and it did had continuity to the speedometer... :mad:

So we can rule the wire out...

And I have a new and exciting possibility for you guys, the darn service manual is wrong!!! :eek:

I had a 100 ohm resistor lying around, so I plugged it in there, instead of the temperature sensor (according to the tables, the resistance decreases as the temperature rises) and guess what? The warning light turns on! Only for a second, then turns off, hit the starter and it turns on again until the engine starts, and then it runs really crappy (limp mode?). I guess that the ECU knows it is way out of range and that it doesn't make sense according to the other sensors (oil temp, IAT), so it goes and turns the fan on at full speed (just as it does when the temp sensor is unplugged, so it goes to temperature sensor failure mode).
 

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It probably ran crappy because the ECU was metering fuel for a hot engine, which it was not.
The fan turned on because the resistor was within fan-on temperature resistance, but not low enough to turn on the light. If you put in a smaller resistor, the light probably would come on.

I have to ask, you never got an FI light during all of this?
 

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Pffftt...


So we can rule the wire out...

And I have a new and exciting possibility for you guys, the darn service manual is wrong!!! :eek:
PLEASE!!! All you guys with '06 900's, do you get this idiot light test when you turn on the key? I bought my bike used with no owner's manual, so I don't know what it says about this test. I downloaded the SERVICE manual which DOES say this light IS supposed to test!
What are your bikes doing? How many have TEMP lights that come on for a couple of seconds when you turn the key ON?

Thanks in advance for taking the time to check your bike out and please report back.:)
 
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