Smoked Cam Sensor

[Wills67]

Hey folks, I just want to throw this out to make sure my thought process is right. Last weekend, the bike lost spark completely after a fairly short ride, maybe 5 miles. I have pulled the cam sensor and it is definitely smoked. Cracking in the potting and the LED housing is melted pretty well.

Now the head scratcher for me. The previous weekend, I lost the headlight and ended up needing to replace the socket and re-make the ground wire. 2 electrical short issues in 2 weeks seems too coincidental. But, I suppose it could happen.

My question is if the VR could be going and I am getting too much juice in the system. My first thought is that is a possibility and that any suspect ground wires could be the first to go. But when I think about the cam sensor, I believe it is fed a regulated 5 Volts from the ignition module. If that is the case, a bad VR shouldn't directly affect the cam sensor.

The bike is an '04 with a little over 22K miles on it. It has been running great lately until this.

I know I could upgrade to the Daytona Twin-Tec, but I just had to pay Uncle Sam. With that in mind, does it make sense to replace the VR? I can/will check it with my meter, but would rather not take the chance of frying anything else if this is a high probability.

I appreciate any inputs!

Cheers

 

[chacha]

The two could be unrelated. best to check out the charging system first. The cam sensor is a standard harley part for your year.

 

[Th3InfamousI]

I would suspect the ignition module to get fried prior to your cam sensor getting fried. Considering the ignition module feeds the cam sensor power.

If i was a betting man I would assume they are unrelated.

More often than not cam sensor is fried due to heat from your exhaust

 

[Wills67]

Cool. Appreciate the input guys. You are confirming my thinking. I will replace the sensor and check the system.

 

[Sven]

Hey folks, I just want to throw this out to make sure my thought process is right.... I have pulled the cam sensor and it is definitely smoked. Cracking in the potting and the LED housing is melted pretty well.

With your generic computer bike, there are two sensors that turn the bikes into a boat anchor>>> The crank or cam sensor(s) = No spark condition.

Now the head scratcher for me... if the VR could be going and I am getting too much juice in the system.

You'd blow the taillight too if your VR was overcharging. Your battery would smell and leak acid. Your battery would expand at the walls. This is a bad working VR. If none were met, coincidence.

... ground wires could be the first to go. But when I think about the cam sensor, I believe it is fed a regulated 5 Volts from the ignition module.

Negative. A cam/crank sensor MAKE VOLTS, they DO NOT RECEIVE volts. Think of it as a pulse generator. It generates a square wave so the computer understands that in a time thing. Idle, it takes time to come around. At full song, that sensor is super pulsing. Get it?

If that is the case, a bad VR shouldn't directly affect the cam sensor.

Correct. Cam and crank spin up to a certain volt and that's all she wrote. It's linear in wave length so the box knows how fast is fast? So it goes something like this 3 wire variable in the basics:

1. Connector not connected = Nope.
2. Wire out of connector = Not that either.
3. Wire short internally/signal out of range = BINGO! A spinning magnetic field into itself and cooks itself hot/cracked bake did you say?/expanding heat. So my guess is how you described it, a crank or cam has to put out a pulse or no heart beat, the black box is the brain, the wires are the spinal cords out to the jobbers like your hands/foot/chew on that.

... does it make sense to replace the VR?

Only if the above acid smells/batt bulge/blown taillight ~ are met. On the other hand, only your volt meter knows for sure. Set at 20v scale and let bike idle. Send probes to correct polarity and idle should read under 15v. Anything over 15-16v is a bad VR.

 

[KaptinAmerika]

Are your Ignition Module and Cam Sensor integrated in the Cam Chest or separate

 

[Wills67]

Hey Sven, Good explanation and thanks for the inputs. The only thing I would question is the voltage going into the cam sensor. Since it is an optical slotted switch, the LED side does need current/voltage to "light up". That's why I was thinking maybe a regulated 5v. Absolutely agree on the output side. I would assume they use a standard phototransistor with a Schmitt Trigger to get the square wave output. The reason I asked about the increased voltage to the LED side was because that will cause an LED to get really hot really fast.

In any case, hopefully this thread could help someone else down the line

 

[Wills67]

Hey Curtis, They are separate. I have the Thunderheart under the seat.

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I ran down and grabbed a new sensor from Amy down at Strokers. Should have her up and running for the weekend.

Thanks!

 

[KaptinAmerika]

Cool

WHat did they charge your for the sensor

 

[Wills67]

PM sent

 

[Sven]

Since it is an optical slotted switch, the LED side does need current/voltage to "light up". ... with a Schmitt Trigger to get the square wave output... because that will cause an LED to get really hot really fast.

No, Wills, I thank you. You schooled me on hysteresis, and yeah, we are in that 5v range, the sine to square, then, is it a frequency deal with the LED's used, or and edge conversion?

Ah, say I have key on and my LED's are lit. Where would they get hot if they stay the same color or brightness with key on. If running, the cs was fine say, are you saying the cs is a resistor so the LED's stay cool? I don't think so. What kept them cool with key on only? They are just there with a preset resistance, stay on, and code or blink, meaning, a code is sent, a downed system has occurred and here are the blinks where to chase?

That trigger deal is for some sort of frequency traffic needing some sorting out. The LED pad with those lights for example. How much traffic we talking? I'm two wires I am a plain old magnet. If I am three wire, I'm hot lead to the inferred, input to the black box and a ground. Are we three or a two wire cs?

 

[Wills67]

My cs is a 3 wire system. I haven't uncorked the potting after letting the smoke out, so I am just doing a little guessing. That said, this is the one part of the system where I might have some additional insight. The company I work for happens to be one of the larger suppliers of custom IR slotted switches. So, being the mechanical engineer I am, I went and asked the EE's

The IR LED should probably hit full power at something more like 2 V, so there is more than likely a limiting resistor in that circuit. I would believe that at key on, the IR LED is on continuously until key off. At the right current/voltage it can run nearly forever without overheating. That said, if it does start to get hot for any reason (exhaust?), the internal resistance of the LED goes up and it starts drawing more current. More current = more heat = more resistance = more current = runaway circuit :angry: I'll have to look up some data sheets and see what a max operating temp range is for most of our LED's.

The receiver could be anything from a simple photodiode to a phototransistor. Either would be a simple ON/OFF when the window appears/disappears. I was guessing at the Schmitt Trigger as a means of making the on/off transitions sharper. It may not be necessary, just not sure.

Dang it. I was just going to install the thing. Now I might have to take it back in to work and see if someone can hook it up to some lab equipment... Then again, I really want to get the bike running I'll go look up some schematics and see what would make the most sense.

 

[Th3InfamousI]

god damnit! I thought we were originally talking apples and oranges.

You guys just took it a bit past me....I dont have a Scooby on what a Schmidt Trigger is.

Regardless at least you got the part oddly enough you would think they are cheap but alas they are not. I think I got a spare in the garage for around $35-40 on ebay once.

 

[Wills67]

Hey, me and Sven are on the same page on this one. But now I have to admit I was schooled by the EE's at work. I am told the heat alone wouldn't cause the melt I had. It had to be a short somewhere on the LED driver. So, that still leaves the question of root cause. My guess is movement in the plastic due to heat and high vibration. Do these engines vibrate? I haven't noticed in any case, if there is real interest, I can try to have them put it under the X-ray and Electron Microscope to find out what failed first. Otherwise, I am just going to put her back together and get riding again. BTW - If anyone is really interested, I can try to figure out the circuit diagram inside that damn sensor and post it.