fan will not turn off

[bonedoc56]

Gentlemen,
This topic has been exhausted, but I can NOT find a solution. I've read virtually every post on this topic. Several years ago Chris from HP Tuners figured something out , but the solution was not made known.
Have a 1966 Chevelle with LS3 with "fast cam" 495hp, using an E38 ECM out of a 2009 Chevy Express van. Have a 4l80E transmission. Vintage Heat/Air system.

Just some background on how this is currently wired. All is going through the SpearTech wiring harness and Dakota Digital BIM and ECM (computer).
Using 2 separate 40 amp relays. The yellow wires are going to the battery with in-line fuses. The red wire is going to the fans + wire. Fans are grounded to the chassis, Battery grounded to the engine. Engine grounded to the chassis and body/frame. (can't have too many grounds. LOL.)
The orange wires are connected to the ignition to activate the relays with the key ON. The gray wires are the ground signal wires..

We used a trinary switch on the AC/dryer.

The GRAY ground wires from the relays are commonly joined and routed and then split with one branch going to the trinary switch on the AC dryer, and the other side of the trinary circuit is to ground, and the other split gray wire is going to the fan#1 wire of the ECM. Remember the gray wires are common. I wanted to activate BOTH fans, on and off together at full speed.
As for the other circuit of the trinary switch, one side goes to the AC/comp and the other side of that circuit goes to the Vintage/Air compressor wire. This is done so that the compressor will only turn on and off based on pressures and therefore with good airflow does NOT kick on when a highway speeds.

Using the HP Editor the fan setting are DISCRETE and set to turn on at 205 and off at 199. I'm running a 180 stat. Cruising on the highway the ECT reads 197-198 degrees. Therefore my fans would and should be off on the highway.

The fan turn on at 205, but even when I get the ECT down to 195-196 with a fast idle the fan does NOT turn off. If I turn off the engine and re-start the fans are off until 205.

When using the HP Scanner mode I can manually turn the fan on and off.

Somewhere in the form I read about a timer set too high and someone's secondary fan would not turn off until that was addressed. I'm wondering if that could be an issue. Even though I have 2 fans, everything is wired as if running only one fan, but using 2 separate relays.

I am completely at a loss. I'm getting help from members on this forum, but I need more help. PLEASE. Anybody from HP Tuners

[Pitbull]

Without a file posted help is limited.

[bonedoc56]

here is the file.

[LS ROB]

Try putting a 0 instead of 10 in the 195.8 column on [ECM] 18030 - Fan Desired % vs. ECT: Desired Fan percentage for a given engine coolant temperature.

[Alvin]

Try this just in case.

Log a/c pressure incase that pin left unused isn't floating. I'm unsure if these are wired direct or from a BCM.

new fan 01_17_25 - Alvin.hpt

[pannetron]

Does your ECU have a valid VSS input so it knows the vehicle's speed? Some ECUs keep the fans on when there is no vehicle movement.

[Alvin]

That is a good point.

[bonedoc56]

Since I'm new to all this ECM and tuning, how do I tell if I have a valid VSS (vehicle speed sensor) input. If I drive the car in scanner mode and if it displays MPH, would that confirm??? Thank you for the suggestion

[bonedoc56]

I left my "tune", any thoughts

[Alvin]

Try the file I posted first.

[bonedoc56]

if that is so, "that some ECU will not turn off fans unless vehicle is above a certain speed" , is that adjustable? and where.
I assume my ecu knows what speed i';m going because it is connect to the Dakota Digital gauges and does record the speed thru the BIM

[bonedoc56]

Back in 2018 Chris from HP Tuners found a solution to this type issue. there was some "hidden" program where the "minimum fan time ON setting " was set wrong. Anyone know how or where to access this setting.

[Alvin]

You had a bunch of funky fan settings that I corrected and I told you to try that first. Did you? That is just as likely the culprit as the VSS thing.

[bonedoc56]

yes. I tried those settings and the same result. Fans turn on, but will not turn off, regardless of temperature unless i turn off the ignition. Then restart the car, the fans will be off until the turn on set point again

[bonedoc56]

also your values as written would have the fans turn on at about 202-203 and off at about 193. I theory that could never work as the car could never get that temperature 193 degrees even blasting down the highway. Want the fans to come on at 206 and off at 199. Highway cruising the temperature gets to 197-199. Running a 180 degree STAT. Thus the fans would turn off at highway speeds

[pannetron]

The transmission will likely have a VSS, probably OEM on that donor tranny or maybe supplied with Dakota Digital kit. That signal can be routed to the Dakota Digital control box so the DD displays will read vehicle speed. Or that VSS signal could be routed to the ECU and then a CAN bus output from the ECU could be connected to the DD box so *both* the ECU and DD box know the vehicle's speed. The CAN bus connection is likely how the DD box gets ECT and oil pressure data. If you can see the correct vehicle speed in the the HPT scanner, the ECU must be getting a VSS signal. You would also have had to set the correct rear end ratio and tire size in the ECU to get the correct vehicle speed. So my questions are, 1) to which device is the transmission's VSS signal physically connected, and 2) does the vehicle speed log correctly in the scanner? Posting a *log* file might help. BTW, I also have a LSx swapped '66 Chevelle...

[relicdew]

new fan 01_17_25 - Edit1.hpt

See if that file works. If you're USING ONE Fan or want BOTH fans to come on at the same temp, then use the PRIMARY fan control wire only to BOTH relays. I see your post in another section and noticed you said BOTH fans are wired together. I wasn't sure if you were taking BOTH the primary and secondary fans to the same relay.

Just try using the primary fan and write calibration for this file. Yes, it has the fan temps raised a bit but just use this for a test first and verify your wiring on the RELAY(S) are correct. Send a picture or diagram of how you have the fans wired if the following tune doesn't resolve your issue.

[Alvin]

also your values as written would have the fans turn on at about 202-203 and off at about 193. I theory that could never work as the car could never get that temperature 193 degrees even blasting down the highway. Want the fans to come on at 206 and off at 199. Highway cruising the temperature gets to 197-199. Running a 180 degree STAT. Thus the fans would turn off at highway speeds

If you never reply we don't know if you even tried.

new fan 01_17_25 - Alvin 2.hpt

[bonedoc56]

new fan 01_17_25 - Edit1.hpt

See if that file works. If you're USING ONE Fan or want BOTH fans to come on at the same temp, then use the PRIMARY fan control wire only to BOTH relays. I see your post in another section and noticed you said BOTH fans are wired together. I wasn't sure if you were taking BOTH the primary and secondary fans to the same relay.

Just try using the primary fan and write calibration for this file. Yes, it has the fan temps raised a bit but just use this for a test first and verify your wiring on the RELAY(S) are correct. Send a picture or diagram of how you have the fans wired if the following tune doesn't resolve your issue.

Both fans are wired together. thru 2 seperate 40 amp relays. The 2 negative trigger wires are joined to the fan #1 wire from the ECM. I'm also going thru a trinary switch. Going to troubleshoot both relays and tribary this week. It gpoing to abve little warmer to work in the garage.

[blindsquirrel]

Trinary switch crap is for standalone, non-ECM controlled fans, you're trying to combine things that were never meant to be used together. Control them with the ECM by temperature and AC pressure, or control them with the standalone add-on gizmos and no ECM.

However hard it would be to add a 3-wire factory style high side pressure sensor it couldn't be as frustrating as trying to make it work with what you have now.