robbied31

iTrader: (1)

Hi,
I have had my LQ4 running since last weekend. I have been double checking all the wiring and so far the only problem I have is my #2 fan. my number one fan comes on at 180 degrees and it comes on when I force it on from within HPTuners PCM controls. Fan #2 doesn't come on. It is being told to come on by PCM at like 200 degrees, but the relay just clicks constantly until I turn it off and as this is happening, the fan turns slightly with every click. click, click, click. At first I didn't hear the click over engine so I thought I had a bad fan. swapped wiring to fans and the #2 fan operates on fan #1 wiring. Then I thought it was a bad relay, but when I swap relays,the same thing happens to the relay controlling #2 fan. I have 12v/switched power to terminal 30 and terminal 86. If I understand correctly, the PCM supplies ground to terminal 85 for control, correct? Any ideas? 30 amp fuses are good and swapped them to check. I also pulled the relay and jumped where terminal 86 plugs into to where terminal 87 plugs into and the fan runs.

Thanks

Rob

robbied31

iTrader: (1)

after searching fan issues, I physically grounded the fan 2 control wire coming from the PCM and the relay engages and the fan operates properly. Do I have a bad PCM?

Rob

cutlass_455

iTrader: (2)

Are you using the 2000 LQ4 PCM?? Did the host truck have dual electric fans (probly not)?? What pin(s) are you using from the PCM connectors?? Im not 100% sure about your PCM, but my 2001 4.8L truck harness / PCM is only capable of operating one fan, and in HP Tuners its FAN 1 / Low Speed Fan.

In HPT have you selected '2 fans' of type of fans??

If yours is the same as mine then, your first fan comes on cuz the pin (Blue connector pin 42?) is not used by the truck harness for anything, and when you use HPT to 'turn it on', it works for fan control. If you are trying to get the second fan to come on from the PCM (red connector pin 33). Red connector pin 33 in MY truck harness is used for controlling the reciculation damper in the heater controls in the dash. Its different inside the PCM and not a switch like on blue pin 42.

Ive attached a couple pics, one is for fan wiring for a F-Body, the other shows the recirc door control for a truck. You can see the one pin is the same between the two and that they are different type of control inside the PCM.

In short, your truck PCM cant control 2 fans like in a F-body. You need a F-body PCM (I think) or get a temp switch setup from Autometer or something like that.

What you can do is make the PCM control both fans at the same time by controlling both of your relays. Its not as an elegant control system, but itll work.

I just went thru this over this weekend in my own project.

robbied31

iTrader: (1)

Cutlass_455,
I appreciate the input! I am using 2000 LQ4 harness and PCM. when I turn fan 2 on in HPTuners, the relay starts clicking. So the command is making red pin 33 ground, it just seems that it is not closing the circuit continuously. lt1swap.com say's that red pin 33 is used for fan 2 when you enable the fans. Also, HPTuners greys out the options that are not available for each PCM. So what I am getting at is I think our PCM's will run two fans, I just haven't got all the info I need yet to figure it out.

Anyone else using LQ4 harness with fans that had a mechanical fan before?

Thanks,

Rob

cutlass_455

iTrader: (2)

If enabling the fans in HPT changes how that circuit works inside the PCM then I guess you would have make sure you got it wired correctly, remember the fans control is a switch on the ground side of the relay. I hope you get it figured out, cuz Id like the same solution. For now Im just gonna run in high speed on / off control. I just wish I knew how to repin the connector, cuz I think Im gonna have to add that wire back.

robbied31

iTrader: (1)

It is wired properly, when I physically ground the fan 2 [pin 33 red] wire with key on, the relay engages and fan operates properly. Also, when I turn fan on in HPTuners, the relay starts clicking. so, I am pretty sure the PCM is just not supplying a constant ground. Maybe the PCM is expecting some other sort of input to stay engaged. We'll get it figured out. Someone will have the answer. I emailed the author of lt1swap.com too. I hope he checks his email regularly

anyone else??????

robbied31

iTrader: (1)

bump?

Shon Herron

iTrader: (25)

interesting, subbing since I am about to do the same thing.
did lt1swap use the OS from the LQx or does he use the F-body or custom OS?

Sounds like the PCM is switching ground (on off) if it is clicking.

I may just wire mine up thru ignition....could run one from ignition and the other one off that relay (blue pin)....

cutlass_455

iTrader: (2)

Have you tried putting a DMM in line and seeing what the current draw is in the red 32 circuit?? Or just measure the voltage?? You might be able to get a better idea of what the PCM is ACTUALLY doing.

robbied31

iTrader: (1)

Cutlass_455,
The pcm was still trying to control the hvac recirc door. After asking here and on HPTuners website, the switch for recirc door to fan #2 is a request for a future build of the software. I had sent in my current tune to suppor at hptuners.com when I requested the beta version and they sent my tune back to me with fan # 2 control enabled. I now have fans 1 & 2 being controlled by PCM on an LQ4 harness and OS.

Although we don't have access to the switch yet, that is some good customer service!!!!!

Rob

hookemdevils22

iTrader: (12)

just so i understand correctly, blue 42 is for the low-speed fan, and red 33 can be used for high-speed on an LQ4 (mech fan) harness? I'm trying to troubleshoot a lack of my fan working right now, and i'm not sure i used the right pin for the fan.

EDIT: brendan (lt1swap.com) comes through yet again! I thought the PCM would supply +12v to the relay, so i wired it wrong. man, these 'pcm supplies ground' circuits are killing me!!!

Pocket

iTrader: (22)

PCM controls 12v for fuel, GRD for fans and AC clutch

More info on them
http://www.thirdgen.org/techboard/lt...formation.html

lrazer

is this enabled in their latest software version yet?

MillsMotorvation

Good info here!!

BlownChevy254

.....Resurecting the deeeeaadd!

Whatever came of this, im having the same click click click...
This is on my 2000 silverado. With the stock old pcm the high speed works as it should. With the new 0411 pcm it just clicks when commanded on high via hptuners. Am I missing something here>>>??

lrazer

Still havent figured it out. Mine doesnt get hot with just the low on but i would like the high to work.

72chevelle6.0

iTrader: (22)

what amperage relay are you guys running?

TomM

iTrader: (56)

Old thread, I know but for future reference....

If you have HP Tuners 2.24 you should be able to toggle the evap door to fans. I don't have it in front of me at the moment, but in your tune file, go to system-fans and at the top it should default to evap. Click the drop down box and toggle the selection to 2 fans/fan 2 or whatever it says...then you need to write calibration to make it stick...



T,

OldCreek

iTrader: (1)

Had the exact same problem....

Went to Hptuners.com and updated my 2.22 version to 2.24 via free internet download....

Opened up my program in the new VCM Editor that was downloaded.

Went to Systems

Went to A/C

Changed the recirc door to Fan #2

Uploaded the changes via VCM Editor

Confirmed the fix by turning on the fan from the laptop via new VCM Scanner

(Obviously, you have had to wire Fan #2 as posted above.)

Awesome! Thanks for this info on this thread!

wild1100

iTrader: (3)

Yes this has fixed my issue as well. Thanks