E38 fan relay controls

[radsixlitre]

Hey All,
I am trying to sort out the fan relay wiring on my E38 PCM. I am running 2 x electric fans and 2 relays. pin 85 (ground terminals) of relays are connected to pins 17 and 58 of the 73 pin PCM plug. I have used these pins based on the VE 6.0 liter commodore diagram I am using. The engine is from a VZ Thunder SS ute (which seems to be part VZ and part VE as quite a few of the wiring colors do not match diagrams I have found)
the way the fans are connected at the moment, one runs all the time and one does not turn on at all, even with ECT at around mid 90 degrees C.
I've found other posts relating to the switching of that fans at different temps and I understand that adjustment using the logic system of the E38 PCM is limited. I would be happy if I can get both the fans to switch on and off at the same time as needed because I am using a stock Rodeo radiator in my conversion and I want to shift as much air as possible when temp gets up a little...
any advice on the correct fan connections would be appreciated.
Thanks,
Dave

[radsixlitre]

Hello folks,
does anyone have any ideas on this one for me? I suspect I have overlooked something so any assistance would be great.
Thanks,
Dave

[Steve Cooper]

Hello folks,
does anyone have any ideas on this one for me? I suspect I have overlooked something so any assistance would be great.
Thanks,
Dave

Hi mate,

I have wired In quite a few VE engines as conversions but never a VZ engine, however I'll see if I can help.

I have always done the fan wiring as per OEM, on a VE it uses 3 relays. Basically, on low speed both fans a fed voltage in a series setup, both fans run at half speed. At high speed they are both fed 12v independently.

It's a little hard to explain, but that's the basics of it.

I'll see if I can find a diagram showing the wiring to help make sense of it a bit better.

[Steve Cooper]

L77 fan wiring.jpg

Found this in all my piles of shit lol

[Steve Cooper]

If you have factory values in your fan tables, and you have 1 fan on all the time something might be up with your fan wiring.

I have run the factory way of running the fans heaps, and if you have a good radiator it will only cycle the low fans most of the time. On the STD OS you can have the low fans come on at 91deg, depending on the type of fans you can hardly hear them cycle.

[radsixlitre]

Hi Steve,
Thanks for the info. I will rejig the wiring I have done and add an extra relay as per your diagram. I am currently only using 2 relays and I reckon that is where the problem is.
The ECU, engine and T56 in my RA Rodeo crewcab are from a VZ Thunder ute, which so far as I can tell is a bit of a cross breed between a VZ and VE as it is the VE engine in the VZ body...this seems to cause a little confusion when I try to find wiring info. I'm on the home stretch now though, its running and driving, just have little jobs like this one to sort.
I'll report back once I rewire it.
Cheers,
Dave

[radsixlitre]

Finally made some time to change my fan wiring as per the diagram Steve supplied. I am confident that it is all correct now because fans can be switched to low, high and off via the HP scanner. However, when engine is running, both fans run on High all the time, even from cold!?
I have read elsewhere on the forum that the GMPP conversions require a speed signal to switch fans off, but it sounds to me as if they will only switch on when engine is at operating temperature and they turn off when speed signal is seen by ECU. (my VSS is not yet connected to speedo - another job on the list)
Is it possible the issue I have is some kind of "fault mode" causing the fans to run all the time. I have done the loom myself and there are numerous wires which are "not required" to make the engine run that are not connected. I cannot see that any of these disconnected wires would be causing the issue, but I would love someone to prove me wrong.
Hope someone is able to set me straight on this one; Thanks in advance for any assistance.
Dave

[radsixlitre]

I have been making some changes to settings in order to sort this issue I have with the fans running all the time. I do not have air conditioning connected as yet, so I was wondering if ECU was running fans because it is not receiving an air con pressure signal. I zeroed out all the fan state/aircon pressure table and changed TPS disable settings in aircon to 5% as a test. This did turn the fans off while engine was running, but as it reached operating temperature the fans did not actuate (I sort of expected this due to the TPS value I entered) I changed TPS values back to 98% disable/95% enable with pressure table at zero and fans run all the time again.
I am able to turn fans on and off with the HP scanner while the engine is running so I am thinking that it is a setting or values in the software somewhere causing the fans to run all the time.
The ECU is not connected to a vehicle speed signal, but based on my wiring diagrams, I don't believe that this variant is connected directly to the VSS (maybe gets a signal via CAN???). I've read up on the fan logic control system, and I am running stock values, so I don't think that is the issue. Once I figure out how to post my tune file, i'll add it so somebody might be able to check it out and see if the issue is there somewhere.
Cheers,
Dave

[radsixlitre]

I know there is an answer to this problem...
here is my file...rodeo fan testing5v4.hpt

[radsixlitre]

I have finally solved the issue of my engine cooling fans running all the time regardless of coolant temperature. I was suspecting that the ECU was switching them on as a result of my air conditioning settings, which proved to be the case.
I was getting P0532 A/c pressure sensor low as a DTC and P0645 A/C clutch; this makes sense because I do not have air conditioning sorted yet.
I changed the setting in the DTCs to no error reported for both and reflashed. The fans now only cycle on and off at low speed at around 105 degrees c
It has not been hot enough to see if they will change over to high speed, but I'm confident they will when needed.
So that job is sorted
I hope this info is of some use to others with a fan issue.

Cheers,
Dave

[Paz]

Good outcome Dave

[SS8UUP]

Your thread was a huge help. I was helping a buddy with his LY5 5.3 swapped 67 C10 using the E38. His fans would run all the time, after finding your thread I checked DTCs and had the same P0532 A/C low limit code. After setting to no error reported the fans function as expected. Thanks