High Speed Fan Issues

[Skye]

I then went to the terminal for fuse 55. No 12V power there either.

are you sure the high speed fan simply isn't being commanded to turn on? That would explain no voltage at fuse 55.

That's what I think. At rest, the circuit is not in use. There is no power. Once the fans are running in series, I would expect to see power through this circuit. Fuse 55 is positioned where it is in-case Fan2 draws too much current. Breaking the circuit at F55 protects the other bits upstream.

Fuse 42, I would expect it to have power at all times. The Battery Junction Box side.

ECT is inferred from CHT on these cars correct? I

In the Coyote, yes. CHT is measured via a thermistor, a temperature-sensitive resistor, on the back end of the passenger side cylinder head. ECT is inferred from that. ECT typically runs cooler than CHT.

You're seeing changing temperature in the gauge and those temps are high enough to trip high-speed ops. I'm thinking the CHT sensor is OK.

What module actually commands the fan? Can you access it and command it to turn the fan on, via scantool or Forscan, to check the module is working?

I like that.

In the chart above, you can see how temperatures can be programmed to have the fans spin at low and high speed. I'm unfamiliar with FORScan programming in the Powertrain Control Module. It'd be great if someone could hock up, go to the correct address, excite the fans to spin at high speed and see what happens.

I've reached the depth of my knowledge. @Houdinii_5.0 has made progress and cleared several areas. Two general ideas...

- If at all possible, flash back to a stock tune. See how the fans act then. Existing physical mods might not allow for this

- Seek out someone with mechanical and programming knowledge, in an attempt to answer the lack of high-speed operation

Sponsored

 

[Skye]

F55 and associated circuit is good; that circuit works during low-speed operation. Fan 2 is spinning then.

F29, F31 and F42 are involved.

F42 was seen as being hot at the Junction box. This fuse supports all three relays.

F29 supports Fan 1, high and low speed. This drop is good, as the fan runs at low-speed.

F31 "hot at all times", I don't believe has been checked. This fuse supports Fan 2, high speed.

Looking at Low-speed and High-speed Fan Control, we know that LFC works. HFC is a question mark.

From the error code, the PCM seems to be alerting HFC to engage, but we know that is not happening.

Edit,

If the fans themselves were bad, it seems odd both would have issues. One, sure. But both...if they were unable to spin on high, I'd think that'd be a physical issue, like blowing fuses and popping circuits.

For the circuitry and the physical thus far, it doesn't seem anything is over-drawing current.

 

[Mach VII]

F31 only supplies power to the high speed fan and only when high speed is commanded (FC2 & FC3 energized), otherwise both fans are in series via F29 (FC1 energized) or both turned off. If F31 is blown then you should see only the low speed fan running once the ECT gets above 223*F and HSF is commanded. Was this working fine then suddenly an issue or has it only appeared after tune or tune revision?

 

[Houdinii_5.0]

F31 only supplies power to the high speed fan and only when high speed is commanded (FC2 & FC3 energized), otherwise both fans are in series via F29 (FC1 energized) or both turned off. If F31 is blown then you should see only the low speed fan running once the ECT gets above 223*F and HSF is commanded. Was this working fine then suddenly an issue or has it only appeared after tune or tune revision?

I'm pretty positive the car has had this code since I purchased it last December. I just didn't think much of it at the time because it had a multitude of other issues and of course it was cooler out so I didn't notice any high CHT issues. It's just a lot more prevalent now that it's hot out and it's one of the last things on my list to address.

The car is tuned by Lund. I already reached out to them, and they verified that the fans should come on earlier than the stock calibration, but that I definitely have a hardware issue on my end if they aren't kicking into high speed.

 

[Houdinii_5.0]

I ended up checking fuse/terminal 31 that y’all mentioned and it was fine. I put 3 new relays in it today and just let it run for a while. This is what forscan showed on live data when CHT was at 200. Says high speed is on and no fault detected now so I’m assuming they’re working again. This was with AC blasting.

Weird thing is when I do the KOEO test and KEOR it will still throw the high speed code. Maybe something about those test don’t trigger the high speed setting correctly. I would think the live data would show a fault if it still wasn’t functioning properly. When I go to read the DTC codes it no longer appears and seemed to be blowing pretty good when I got out to check.

Sponsored