Single ftermarket fan won't turn on in C5 Z06

[Supercharged111]

I installed a Spal fan to replace the dual factory monsters. It tucks up in there real nice and probably flows enough to suck the car forward. . . when hooked directly to the battery. Problem is the bastard won't kick on in the car. I've tried it in both series parallel mode and aux fan mode, I've attached 3 tunes that failed to turn the fan on. Schematic is below, I see no reason for it not to work so it must be some retard logic inside the PCM.

http://www.motortopia.com/files/17204/album_wiringdiagrams/4c51a236c1209/CoolingFans04.jpg

Fan mod is failed attempt #1, I kept it in series parallel here but changed the values to prevent fan#1 from ever coming on. I also changed the AC pressure values so fan #2 would more closely mimic the function of fan #1.

Aux fan is failed attempt #2, only change here was switching it over to aux fan mode.

Aux fan 3 is the 3rd and current failed attempt, I plugged all stock information back into the fans (trying to outsmart the logic here) and just brought fan #2 down to kick on at the same coolant temp as fan #1.

I'm plugged into the right side fan plug and the left is just wrapped in tape. I'd like to get some factory style connectors on there, but for now I just need to get the damn thing working.

[joecar]

Have you tried connecting it as Fan Left and using the Fan Low parameters...?

[Supercharged111]

That's my next COA, it was getting late to keep starting the car.

[joecar]

Have you tried connecting it as Fan Left and using the Fan Low parameters...?I just realized this won't work unless the Fan High socket is shorted.

[Supercharged111]

Yup, I'm sure I've got one made up in a bag right now that'd be plug and play. I also need to yank relay 43.

[joecar]

Low speed fan mode (series) won't work unless both fans are present, High speed fan won't work unless Low speed fan is the current mode...

[Supercharged111]

You're not deriving that from the schematic are you? If that's the logic in the PCM then it must know when the fans are actually running in low speed mode and not just commanded to. Unless low speed turn on temp must be lower than high speed, I can try flashing that on before plugging into the left side and shorting the right.

[joecar]

Yes try that (low speed on temp below high speed on temp).

[Supercharged111]

It worked! With the A/C on anyway, wouldn't do that before so I think I'm good now. I was able to confirm it was wired backwards too, so got that rectified as well. I'll go back in there now and tweak on the A/C temperature as well, but it seems that was the logic that prevented the PCM from kicking on the fan. I'd really like to know if the aux fan mode could be utilized? Or would that need to be controlled via the low speed plug?

[Supercharged111]

It seems to work on all fronts, just need to verify if it's turning off at speed or not since the high speed version was a little different. The new fan is pretty loud, but what's more impressive is that it will suck a piece of paper right off the floor now! I think I'll need to install a screen down at the inlet, something I've been wanting to do for a while anyway.

[joecar]

Good job :cheers: