Hello jbody.org I am fairly new to you guys and i have a question.(a little backgroung first.) I recently installed a cooling fan bypass following Wild Weisel's directions and it works great. The only difference in my setup is that I added a LED light bulb to indicate that the fan is on. I wired this led light from the ground wire(for the relay) I installed per the instructions. The Positive wire for the LED is always live and I stole that from the cig lighter. The LED functions properly; turns on when I flick the switch.
Now my question what I can't figure out... When I turn the engine on (bypass switch off), as soon as I stop the starter motor the LED turns on for maybe 1 second. (then turns off). Because the ground from the bypass switch is isolated when the switch is off; the only thing I can think is that the pcm is providing a ground for that less than 1 second flash. Do you know if the pcm does a diagnostic check of the cooling fan system during start up? Is there anything I'm maybe missing? Is it anything to worry about? I don't think its great that during start up the cooling fan switches on for a half second, but I don't understand how else it is flicking on if that is not a normal function of the pcm/bcm. I hope I have not lost you I did my best to explain this complicated matter.
Thanks
why didn't you just get a light up switch i used the instructions in the JBO liabrary and used a switch with a light on it
JBO since July 30, 2001
why dont you just answer his question?
i have done the weasel fan bypass myself and it works great, but i dont have an LED on mine. i went with an all black solid non lighted switch. i find it fits in better with the interior of the car and is less noticeable.
as for your problem, many auto manufacturers turn the fan on at start up. alot of them even keep it running if the car is too hot. the light switching on and off at start up is probably just something you will have to live with and is some inherent feature that comes with the wiring the bypass the way you did. my one suggestion would be to look at your wiring.
i know you have the 12V of the LED a constant from the cig lighter, which is fine. the thing that i would question is your ground. i think you have it on the wrong side of the switch.
on the switch you should have 2 pins that need to be used. if you have a 3rd pin on your switch it is because it contains an internal LED which your not using if you mounted another LED for this system.
so...
pin 1 - wire from harness from ECU
pin 2 - to ground. grounds out fan.
if you were to wire the LED to pin 2, it would constantly be on as the circuit would always be complete.
if you wire to pin 1, when the ECU switches the ground at start up your fan flashes on.
what you will need to do more than likely (if im right) is add another diode in line with the second ground circuit you created for your switch and LED. so, as it seems, you need to add another diode to block the current from the 12V cig lighter and the fans original ground in the ECU. an easy way to figure if ithis is your problem is to see if the light comes on when the fan switches on at other points in time. does the LED come on if you turn on the a/c? or the fan switch on its own? if it does, then i think i might be right... but its still too early in the morning to tell lol.
1997 Cavalier Z24
Bomz Short Ram Intake
Vibrant Cat-Back
KYB GR2 Struts
Goldline 1.75" Springs
RK Sport Upper Insert
RK Sport Lower Dogbone
Custom Tune by Shane @
innovativetuning@rogers.com
15.647 @ 88.02 MPH
If you tie your LED to the GND side of the relay, it will light up any time the fan is on, whether its because of your switch or the ecu.
Tie the gnd side of the led to your gnd wire but just before your switch. Put a diode on your ground wire going to the switch as well. This was the LED can only turn on when there is a ground PROVIDED BY the switch and cannot turn on when the ground is provided somewhere else by back tracking up that wire and over to the other ground.
So from the ground wire coming out of the relay, (I think dk green if memory serves) it should go:
RELAY>> -------------DK GRN---------------------DK GRN----------------------------->>ECU
|
|
+ |
DIODE
- |
| - +
|-----------------------------------------LED------------------->> +12V CIg.Lighter
|
SWITCH
|
GND
I really hope that all lines up when i post this. if you still have trouble, let me know and i can draw it out and post a picture.
----------------------------
<<<<<2003 Sunfire Sedan>>>>>
RELAY>> -------------DK GRN---------------------DK GRN----------------------------->>ECU
......................................................................................|
......................................................................................|
...................................................................................+ |
................................................................................DIODE
....................................................................................- |
......................................................................................|...............................................-............ +
......................................................................................|-----------------------------------------LED------------------->> +12V CIg.Lighter
......................................................................................|
................................................................................SWITCH
......................................................................................|
...................................................................................GND
That's much better... Should have previewed first time!
----------------------------
<<<<<2003 Sunfire Sedan>>>>>
Adam Kappheim wrote:RELAY>> -------------DK GRN---------------------DK GRN----------------|original diode|------------->>ECU
......................................................................................|
......................................................................................|
...................................................................................+ |
................................................................................DIODE
....................................................................................- |
......................................................................................|...............................................-............ +
......................................................................................|-----------------------------------------LED------------------->> +12V CIg.Lighter
......................................................................................|
................................................................................SWITCH
......................................................................................|
...................................................................................GND
That's much better... Should have previewed first time!
1997 Cavalier Z24
Bomz Short Ram Intake
Vibrant Cat-Back
KYB GR2 Struts
Goldline 1.75" Springs
RK Sport Upper Insert
RK Sport Lower Dogbone
Custom Tune by Shane @
innovativetuning@rogers.com
15.647 @ 88.02 MPH
Good catch on the original diode whitegoose, thanks!
----------------------------
<<<<<2003 Sunfire Sedan>>>>>
The ECU test's the A/C for a brief moment on start up, which will turn the fan on as well for a brief moment.
FU Tuning
thanks for verifying that john. i guess that answers your question and solves your problem all in one shot, huh? lol
1997 Cavalier Z24
Bomz Short Ram Intake
Vibrant Cat-Back
KYB GR2 Struts
Goldline 1.75" Springs
RK Sport Upper Insert
RK Sport Lower Dogbone
Custom Tune by Shane @
innovativetuning@rogers.com
15.647 @ 88.02 MPH
Ok so the ecu tests the a/c during startup, which activates the fan. That makes sense. Thanks a lot i am going to comfirm that in my service manuel but i figured the ecu had to be responsible for that.
I also just wanted to say i am super impressed by the response i got to this, I posted last night at like 10 and when i'm home from work today i already have my answer.
thanks guys
