Electric fan wiring question

[pnhigg]

I have a 5.3 in a 92 fullsize.

I have added a single electric fan.
I have it connected to what I understand to be the high speed fan signal (red connector #33). I had to add the pin to the truck pcm
Also from what I can tell the fan should come on at 200 and off at 195. (so my tune file says)

I get nothing when the truck heats up.

I also had the a/c wired to kick the fan on when the compressor was engaged, but I am getting nothing.

Anybody have any ideas.


I have a 75amp relay with constant 12 volts entering pole 30
(87) to the fan
(86) to a ignition on 12 volt source
(85) pin 33 red connector on the pcm.

Any ideas why this isn't working.

[Eddie-98GTP]

What did the PCM come out of? Can you ground pin 85 of the relay and make the fan come on?

[pnhigg]

Thanks,

The fan will run if I ground 85.
I am pretty new to hptuner, as you will quickly see, but I changed from aux fan to 2 fans and now when the temp is reached I am getting a pulse-like signal. The pcm is grounding on/off about every half second or so consistantly.
You can hear the relay clicking every 1/2 second.

Any ideas what that could be?
My connection for the ignition is the ignition on for the original cruise control.
The #30 and #87 poles are 10ga wire straight from the constant power bar, and the pcm signal is hooked up to 33 on the red connector with an 18 ga wire.

[Eddie-98GTP]

What did the PCM come out of? What is it programmed for? Depending on which PCM it is, that could be normal.

[pnhigg]

Came out of a 2001 fullsize truck.

Thanks

[Eddie-98GTP]

It's very possible, since the truck it came out of did not have an electric cooling fan, that this will not work. There is an alternitve however, if you don't mind the fan coming on at 212*F. A NAPA FS112 fan switch will ground at 212*F. You could run a wire from this switch to pin 33 on your relay and it should work.

[Eddie-98GTP]

Found this also - it may help if you intend on going the fan switch route

02-4026 Hypertech Cool Fan Switch [cuts on at 176, off at 166 degrees F] $39.99

02-4028 Hypertech Cool Fan Switch [cuts on at 200, off at 185 degrees F] $39.99

Jet Summit P# JET-60600 on at 200* off at 185* $38.69

[Nitrous]

On the PCM's blue connector, PIN #42 should be an open slot. Did you get your harness from Nelson or built it yourself. The Nelso harness will include the proper pin, you just add it to the plug and run your power and ground then an A/C tap (to control fans with A/C) and your done, you can tune the fans using HPTuners. Just a thought.................................

[pnhigg]

Thanks guys.
The #42 pin worked. Found out that with a truck pcm you have to use the primary fan control not the secondary for a single fan.
My understanding was to use the secondary if you were wiring only one fan.

I know I can tap into the relay to get the fan to start when the a/c is engaged, but I have another question.

I have am currently using the original 1992 a/c systmen that did not use the pcm to control the compressor cycling, but used a low pressure switch.
I would like to know how to let the pcm know that the clutch is engaged so that the idle rpm will increase, as the truck pulls down a good bit when the clutch is engaged. It also seems that the pcm should signal the #42 to ground when the a/c is on.

Any suggestions there.

Thanks again for all the help to this point.