LS3 fan stays on.

[patrick335d]

Hi Guys,

I have GMPP LS376-525 with the GMPP controller and wiring harness.
The engine is equipped with a 160F thermostat.

Once my temperature reached 203F the fans will start and cool the engine down, all perfectly well.
but the problem is that they never stop, it will pull the temperature down all the way to 150F.
the water in the radiator is getting stone cold, due to the continuous running of the fans.
To stop the fans, i need to kill the engine and restart it.
Its getting pretty annoying, I have been fiddling myself with it.
Then I had contact with some guys on LS1tech, who advised to change some parameters.
I tried these aswell, no luck so far.
I hope you guys got some ideas.

FYI, in VCM Scanner, i can control the fans without any issues on and off, it works fine.
Only the ECU control not.

attached the original GMPP software.
and the latest on modified by Ross Kemp.

thanks patrick

[schpenxel]

Does it do it on both tunes?

Are there any codes? There are a few weird ones that can pop up that make the computer think the coolant temp sensor aren't working correctly and it turns the fan on wide open to try to keep things cool. Just a thought.

Set the lowest cell of the ECT vs. fan desired table to 0. You can ramp it up in the next cell or just leave it at the ~40%.

Leaving the lowest cell at 40% will make it run all the time I'm pretty sure

[Jon S.]

The newer GMPP harnesses merge (splice) the Fan 1 (low) and Fan 2 (high) outputs from the ECM. They feature only a single wire fan trigger for the user to connect.

Try the settings in the JPEG below ... you are not alone - this is a fairly common issue with the GMPP kits.

[patrick335d]

Does it do it on both tunes?

Are there any codes? There are a few weird ones that can pop up that make the computer think the coolant temp sensor aren't working correctly and it turns the fan on wide open to try to keep things cool. Just a thought.

Set the lowest cell of the ECT vs. fan desired table to 0. You can ramp it up in the next cell or just leave it at the ~40%.

Leaving the lowest cell at 40% will make it run all the time I'm pretty sure

yep, i tried both files, no differences.
and no DTC logged faults or anything.
MIL light is also not comming on, in the scanner function also my ECT is working correctly.

[patrick335d]

The newer GMPP harnesses merge (splice) the Fan 1 (low) and Fan 2 (high) outputs from the ECM. They feature only a single wire fan trigger for the user to connect.

Try the settings in the JPEG below ... you are not alone - this is a fairly common issue with the GMPP kits.

You are correct, I only have the blue wire connected to 2 parallel relays to control my fans.
I will change the file, testing i can do only in a few days, as i have my trans apart at the moment.
I will let you know, thanks for the effort so far.

[patrick335d]

Hi guys,

I tried these settings aswell, but no change.
anyother ideas?

[schpenxel]

Did you try setting the lowest cell in the fan desired % table to 0? Can't hurt to try.

[patrick335d]

I tried it No joy.
if been fiddling with the fan rpm, in the scanner.
the fan engages at 45% and deactivates at 36%. i tried these settings.
Also no joy.
It cant be that hard right, it should work.

[R8SVton]

Set your 192F-199F to 0 and from 203F-250F set it to 91

[patrick335d]

I have been tryling this evening again, to get it working.
No Joy, I tried so many variations, but non seem to work.

There is one thing i noticed that something weird is going on.

engine is idling and get up to 199F and the fan starts, cooling temp starts to reduce.
I go to controls and control the fans normally.
fan 1 I click off, the fan goes off, i click again to remove the red bar and the fan starts again.
fan 2 works excactly like fan 1.

i never tried fan 3 as i thought it wasn't connected.
when the fan is running and i click: fan 3 on. the fan stops.
Is there here a fault in the logic, or a matter of applying to positives to 1 relay coil?
when i remove the status from green to red it runs again, it doesn't stop on red.

any ideas?

[oversteer]

Anyone solve this ?

...i have a ls3 525hp engine does the same....tried everything suggested.

[Jon S.]

The later GMPP calibrations will cause the fan to operate constantly once initially activated, unless the ECM sees a vehicle speed of 15 MPH or more. This was done by GMPP to prevent the fan from cycling on and off at a stationary idle.

There is obviously a parameter for this, but it is not available in the software.

Also, I never thought to check for a "timer" when I had access to one of these vehicles.

As a test, try placing jack stands under the rear axle (block the front wheels - safety first !). Then drive the rear wheels to a speed of 25 MPH or so. If the fan stops nearly instantly (if below the temperature threshold), then there is likely no timer. If there is a delay in the fan turning off, repeat as necessary to determine the exact number of seconds delayed.

With this information to work from, perhaps HPT could add these parameters.

[07GTS]

fan desired % must be below fan state % in they lowest cell for it to shut off, essentially it's all just a on/off fan 1 and on/off fan 2 bit it uses a desired% for switching so just use the same switch points as factory but shift the ect points to suit your on/off temps u want, any over 50% turns fan 1 on then anything over 90 turns fan2 on, i have good settings for a 160 deg stat if u have the 2 bar OS so the fan temps go lower to suit 160 deg

[oversteer]

The later GMPP calibrations will cause the fan to operate constantly once initially activated, unless the ECM sees a vehicle speed of 15 MPH or more. This was done by GMPP to prevent the fan from cycling on and off at a stationary idle.

There is obviously a parameter for this, but it is not available in the software.

Also, I never thought to check for a "timer" when I had access to one of these vehicles.

As a test, try placing jack stands under the rear axle (block the front wheels - safety first !). Then drive the rear wheels to a speed of 25 MPH or so. If the fan stops nearly instantly (if below the temperature threshold), then there is likely no timer. If there is a delay in the fan turning off, repeat as necessary to determine the exact number of seconds delayed.

With this information to work from, perhaps HPT could add these parameters.

Ok will test this on dyno tomorrow....getting tuned on e85 with a 6870(1100hp turbo).

I don't see why gmpp would stop fan cycling while stationary...engines cold enough why keep running fan, retarded !

[oversteer]

fan desired % must be below fan state % in they lowest cell for it to shut off, essentially it's all just a on/off fan 1 and on/off fan 2 bit it uses a desired% for switching so just use the same switch points as factory but shift the ect points to suit your on/off temps u want, any over 50% turns fan 1 on then anything over 90 turns fan2 on, i have good settings for a 160 deg stat if u have the 2 bar OS so the fan temps go lower to suit 160 deg

I understand all that...more than i want too ! lol, its not a simple parameter error, something else funky is going on with this gmpp setup.

[07GTS]

i had a good go at mine a while ago got it to come on when i want and turn off and stay off if under fan 1 on temp, what do your tables look like ?

[oversteer]

Tried many different ways, last being like post 3 in this thread... if you have it working right, question is what do your tables etc look like ? please

[07GTS]

yea mine are quite different to those tables ill get some pics up when im back at the lap top, that fan output control should be staggered having a "1" for both in same column makes both come on high speed first the fan2 should have "0" "0""1" so it's a low fan first then high fan second

[07GTS]

these are my settings fan 1 is on at 81 deg fan 2 is on at 85 deg and then fan 2 off at 81 deg and fan 1 off at 79 deg

[oversteer]

Hmm that's pretty much the same logic as i am using, i only have one fan output...the gmpp wiring harness has one fan relay and output, by the looks of it you aren't using a gmpp kit, this issue is specific to gmpp e67 ecm's for some reason !

What does the main/start fan page look like(where it has discrete etc) ?