Help me understand fan module testing
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Instructor
Joined: May 2014
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From: GreatFalls Mt
Help me understand fan module testing
So i got the melted plug for the fan control module so i hardwired it. I still cant get the fans to come on.
I supplied 12v directly to fans. Fan turns on
I tested for 12 volts at the chassis connector. 12v present
I commaded fans on with hptuners after hard wired connections. Nothing.
I installed a test lamp between the positive wire on the chassis connector to the trigger wire and commanded fans on from zero to 100% and nothing.
I installed a test lamp between the positive and negative on the chassis connector and test lamp illuminated.
With these tests done i believe the ecm is bad because it is not sending a signal down the trigger wire.
Any other test i can do?
Also does the command fan on function work in hptuners. Ive never used it before but i believe it should work or it wouldnt be there.
I supplied 12v directly to fans. Fan turns on
I tested for 12 volts at the chassis connector. 12v present
I commaded fans on with hptuners after hard wired connections. Nothing.
I installed a test lamp between the positive wire on the chassis connector to the trigger wire and commanded fans on from zero to 100% and nothing.
I installed a test lamp between the positive and negative on the chassis connector and test lamp illuminated.
With these tests done i believe the ecm is bad because it is not sending a signal down the trigger wire.
Any other test i can do?
Also does the command fan on function work in hptuners. Ive never used it before but i believe it should work or it wouldnt be there.
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Joined: Dec 2013
Posts: 12,506
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The RD/OG wire on the PWM connector is the ECM control wire, and it passes through connector C182 and C186 before it gets back to the ECM on pin 58 (E38ecm).
The ECM controls the PWM via the modulation grounding on the Rd/OG wire on ECM 58, and not by sending power on that wire to the PWM isntead.
So if you have power and ground to the PWM, the fan will run when it sees direct power, then 12v test light to pieces the shielding on the PWM RD/OR connector wire to get a wire connection from the test light and touch the probe on the test light to ground to supply a ground to the control wire.
If fan runs with control wire grounded, then problem is control wire back to the ecm through the two connector and pins pointed out above.
Also, if the car has been turned, there are a number of factors in the Tune that will tune the fan off even if the motor is hot. The quick check to see if the ECM is really controlling the PWM, it to start the car, and turn the A/C. Here there is a setting in the tune that will turn the fan off from A/C turn-on command, but most tuners will not go near that specific setting most of the time instead.
C186 connector is next to the the battery on a wet sump motor on the fender wall (about half way up the side of the battery), and C182 is by the ECM itself.
http://garage.grumpysperformance.com...nds-etc.10092/
Cooling wiring schematic if you need it,
http://www.mediafire.com/file/0vzf5b...g%20wiring.pdf
The ECM controls the PWM via the modulation grounding on the Rd/OG wire on ECM 58, and not by sending power on that wire to the PWM isntead.
So if you have power and ground to the PWM, the fan will run when it sees direct power, then 12v test light to pieces the shielding on the PWM RD/OR connector wire to get a wire connection from the test light and touch the probe on the test light to ground to supply a ground to the control wire.
If fan runs with control wire grounded, then problem is control wire back to the ecm through the two connector and pins pointed out above.
Also, if the car has been turned, there are a number of factors in the Tune that will tune the fan off even if the motor is hot. The quick check to see if the ECM is really controlling the PWM, it to start the car, and turn the A/C. Here there is a setting in the tune that will turn the fan off from A/C turn-on command, but most tuners will not go near that specific setting most of the time instead.
C186 connector is next to the the battery on a wet sump motor on the fender wall (about half way up the side of the battery), and C182 is by the ECM itself.
http://garage.grumpysperformance.com...nds-etc.10092/
Cooling wiring schematic if you need it,
http://www.mediafire.com/file/0vzf5b...g%20wiring.pdf
Last edited by Dano523; Sep 10, 2018 at 06:52 PM.
Thread Starter
Instructor
Joined: May 2014
Posts: 117
Likes: 7
From: GreatFalls Mt
The RD/OG wire on the PWM connector is the ECM control wire, and it passes through connector C182 and C186 before it gets back to the ECM on pin 58 (E38ecm).
The ECM controls the PWM via the modulation grounding on the Rd/OG wire on ECM 58, and not by sending power on that wire to the PWM isntead.
So if you have power and ground to the PWM, the fan will run when it sees direct power, then 12v test light to pieces the shielding on the PWM RD/OR connector wire to get a wire connection from the test light and touch the probe on the test light to ground to supply a ground to the control wire.
If fan runs with control wire grounded, then problem is control wire back to the ecm through the two connector and pins pointed out above.
Also, if the car has been turned, there are a number of factors in the Tune that will tune the fan off even if the motor is hot. The quick check to see if the ECM is really controlling the PWM, it to start the car, and turn the A/C. Here there is a setting in the tune that will turn the fan off from A/C turn-on command, but most tuners will not go near that specific setting most of the time instead.
C186 connector is next to the the battery on a wet sump motor on the fender wall (about half way up the side of the battery), and C182 is by the ECM itself.
http://garage.grumpysperformance.com...nds-etc.10092/
Cooling wiring schematic if you need it,
http://www.mediafire.com/file/0vzf5b...g%20wiring.pdf
The ECM controls the PWM via the modulation grounding on the Rd/OG wire on ECM 58, and not by sending power on that wire to the PWM isntead.
So if you have power and ground to the PWM, the fan will run when it sees direct power, then 12v test light to pieces the shielding on the PWM RD/OR connector wire to get a wire connection from the test light and touch the probe on the test light to ground to supply a ground to the control wire.
If fan runs with control wire grounded, then problem is control wire back to the ecm through the two connector and pins pointed out above.
Also, if the car has been turned, there are a number of factors in the Tune that will tune the fan off even if the motor is hot. The quick check to see if the ECM is really controlling the PWM, it to start the car, and turn the A/C. Here there is a setting in the tune that will turn the fan off from A/C turn-on command, but most tuners will not go near that specific setting most of the time instead.
C186 connector is next to the the battery on a wet sump motor on the fender wall (about half way up the side of the battery), and C182 is by the ECM itself.
http://garage.grumpysperformance.com...nds-etc.10092/
Cooling wiring schematic if you need it,
http://www.mediafire.com/file/0vzf5b...g%20wiring.pdf
Last edited by Garmans12valve; Sep 10, 2018 at 07:45 PM.
Race Director
Joined: Dec 2013
Posts: 12,506
Likes: 3,634
You sir are a wealth of knowledge. Not gonna lie that was a lot to take in and before i dove into troubleshooting based off your information i decided to just plug it all in and turn the ac on as it was easiest to see what happens. Well started the car turned AC on and fans work. Turned ac off fans still work. So i am assuming that the hard wire connnections fixed the issue but i am still lost as to why my test determined the ecm bad. Probably because i dont know how to read the results. Now to put the car back together to drive it around and see how it works. Thank you for the information you have provided. I should of just done the hard wire connections and plugged it back in and drove around to see how it works but i had to start testing immediately.
Hence in control circut's 101, using the ground side for modulation or breaking the circuit, not the positive side, ends up with a lot less RF noise as the module switches on and off.
The HVAV blower motor works the same way through the HVAC controller.
Down load the one liner PDF I linked below and take at the ECM control wire. It shows that it providing pulsing grounding to the control wire back to the PWM, not positive instead,
http://www.mediafire.com/file/0vzf5b...g%20wiring.pdf
Last edited by Dano523; Sep 10, 2018 at 07:56 PM.
Thread Starter
Instructor
Joined: May 2014
Posts: 117
Likes: 7
From: GreatFalls Mt
I never supplied 12v to the trigger wire. The only thing i did was command the fan on and hook the test lamp between the big red wire on the chassis connector and the trigger wire. The result was the test lamp did not light up.
I am still confused on how the fans work but i cant get the test lamp to light up. I have a trouble ticket in with hptuners to see if they have a fix for my mpvi pro not commanding the fans on
I am still confused on how the fans work but i cant get the test lamp to light up. I have a trouble ticket in with hptuners to see if they have a fix for my mpvi pro not commanding the fans on
