Help: Electronically Challenged

[CYNCRZR]

and that's the least of it, seems I've posted this in bout every forum... apologies to the mods. we'ren't my intention

I'm not the sharpest tool in the shed to start with, so trying to diagnose anything that involves electricity... well....

'03 Sprint ST.

I got 2 minor (i hope) issues.

1) How do I test the thermostat for the electric fan. Seem like if I sit at a long light the temp comes up... past 1/2 way, but I don't hear the fan. I do remember hearing it last summer.


2) The front brakelight switch doesn't work. I own a cheap multi-meter but don't know how to use it to test the switch.

Anyone got enough patience to explain it to me ?

[oldndumb]

I do not know what the operating fan on temp is for your bike, but I would guess it is in the neighborhood of 103c/217f. If you are not sure it is running, you should be able to get the bike up to temp and look at the fan blades to see if they are spinning.

To check your brake switch circuit, start at the closest connector to the switch, and work your way down circuit toward the load. Set the multimeter on "continuity" which will probably be indicated by a Ground symbol. Then turn the meter on and touch the probe tips to verify that it is working. You should read zero and, depending on your meter, hear a buzzer. That should set you up to do a continuity test. That is also the indication you will see if the switch is working properly.

ALWAYS DO CONTINUITY TESTS WITH THE IGNITION SWITCH OFF.

If you can determine which is the positive wire, touch the positive (red) meter lead to it and the back to ground. While someone squeezes the brake lever, you should see the meter go to zero and hear the buzzer.
If you cannot determine which is positive, just do the test twice, switching the probes around. One of the two tests should give you a zero reading indicating the switch works.

If none of this makes sense, post a picture of your meter.

BTW, this is not electronics. It is basic one wire electricity.

[CYNCRZR]

OldnSmarter than me, I'm fraid to admit I never learned even that much... I need to.

I think I can follow those instructions. so if it fails those tests it's the switch if not, then it's further downstream.

Normally the fan is so loud you can hear it when stopped, so I'm wondering if the thermostat failed or ?

I guess I'd find the probe, boil some water and see if it kicks the fan on ?

I spose I could also put a 12 volt battery to the fan motor and see if it spins ?

Thanks for the explanation. The Sprint is my daily driver and I need to take good care of it.

[DEcosse]

Two simple tests, neither will require using your meter:

1) Brake switch
Pull the two small wire connectors off the switch on the bottom side of the brake master cylinder: touch them together and see if the brake lights (if the two conductors don't touch connect a paper clip or something between them) - if it does light, then your switch is bad. If not, report back & we'll go to the next step.

2) Fan
The fan normally has constant power & the ECM supplies the ground to energize the fan. Take a a piece of wire and push it into the connector plug that has the black/yellow wire (NOT the brown/pink one!). Then touch the other end of the wire to the engine or frame - the fan should run.

Incidentally the thermostat has nothing to do with the fan- the water temp sensor is processed by the ECM & tells the fan when to turn on/off. The purpose of the thermostat is to allow the bike to reach operating temperature quicker, by restricting the water flow until it opens up.

[oldndumb]

You could put the probe in boiling water and look for an increased resistance reading. Measure the resistance cold, and then put it in boiling water and look for 200 to 400 Ohms.

You could also disconnect the fan, run the bike up to normal fan on temp, and see if you have any voltage at the plug.

But if it were me I'd start with the fuse, then check the relay, and then check the fan as you suggested. You can also check the fan for an internal short with the meter. They have been known to crap out and not blow the fuse.

[Calliway]

Very good point Decosse, the fan doesn't have anything to do with the thermostat. It is the thermal fan switch that turns on the fan at the right time as all of you have said.

All of these switches are just power in power out so it shouldn`t be to hard to diagnose. I will say that the fan on my 05 is quiet. If the bike is running at idle you hear it but if you are rolling you feel it more then hear it.

I really have nothing to add I just wanted to renforce what Decosse and OnD are saying.

[DEcosse]

Originally Posted by Calliway

...the fan doesn't have anything to do with the thermostat. It is the thermal fan switch that turns on the fan at the right time as all of you have said.

All of these switches are just power in power out ....

Not quite Calliway - it's not actually a switch, but a temp sensor whose resistance varies with temperature - actually called a Thermistor. That is the same one that reports ultimately to your temperature gauge. It doesn't actually go directly to the gauge (or the fan) however but is processed by the ECM. The ECM then has multiple outputs for that input signal - one internal for the fuel adjustments, one for the temp display (which is analog) and the other which is digital to the fan once it reaches the preset value in the program to enable the fan (the output signal turning from "Hi' to 'Lo'.) i.e. The 'switch' part is an electronic one actually taking place inside the ECM, when the actual temp exceeds the preset value. Also of interest is that you can actually change the preset value(s) if you have a Tuneboy. (It's pretty hot in CA in the summer so I program mine to come on at about 5 deg lower)

So - if the temp gauge is rising as the bike warms, you can pretty much rule out the sensor as the issue.
Next step in the chain is the ECM - Failures of the ECM output drivers is EXTREMELY rare - they have short circuit protection built in.
That would still leave the possibility that there is no power to the fan, or the fan is open circuit. The test I described in my post above will determine which avenue to pursue.

I'd be betting that
1) there's nothing wrong, just not hot enough. If the ground wire to the fan test works then just let it idle & it should ge there soon enough - just keep eye on the temp gauge to be on safe side.

2) If it fails the ground wire test, the fuse is blown.

[CYNCRZR]

Hey y'all good stuff there, thanks! This ought to put me on the road to sorting it out.

One last Q. I forgot to ask, someone said I can adjust the amount of pressure (or peddle) travel required for the rear brake light to come on... by turning the nut on the rear brakelight switch ?

Thanks again, I appreaciate the help!

[Calliway]

[quote=DEcosse;972540]Not quite Calliway - it's not actually a switch, but a temp sensor whose resistance varies with temperature - actually called a Thermistor. That is the same one that reports ultimately to your temperature gauge. It doesn't actually go directly to the gauge (or the fan) however but is processed by the ECM. The ECM then has multiple outputs for that input signal - one internal for the fuel adjustments, one for the temp display (which is analog) and the other which is digital to the fan once it reaches the preset value in the program to enable the fan (the output signal turning from "Hi' to 'Lo'.) i.e. The 'switch' part is an electronic one actually taking place inside the ECM, when the actual temp exceeds the preset value. Also of interest is that you can actually change the preset value(s) if you have a Tuneboy. (It's pretty hot in CA in the summer so I program mine to come on at about 5 deg lower) [quote]


Ahhhh I was just trying to support your comment Shouldn't have use the term "thermal fan switch". I was thinking of my Intruder when I wrote that which had no computer control and used a thermal fan switch and to this day they still call temop sensors fanswitches in the parts books which is wrong.

[deller4210]

OND, troubleshooting champ!