Electric Fan Help

[jsett83]

All,

I am having issues getting my electric fans to work for my LS swap. I am running 2 14" fans with each having only a positive and a ground wire. I grounded the black wires to the radiator support, so I know that is not the issue. My programmer stated he set up the PCM for one fan to come on at 205 and the other at 210. Problem is only one comes on, and I have given the engine ample time to heat up. I have attached the 2 relay diagram to show how I hooked up the relays. I have also verified both fans work. I do not have a lot of wiring experience so any info is greatly appreciated.

[Crash_OK]

This is not exactly the way I would have wired them, but it should work. Is the temperature getting up to 210F, if so is the high speed wire from the PCM going to ground?

[Houston Ben]

I was going to say the same thing, if my engine is seeing 210F something is not working/flowing correctly or I loss some water. These engines seem to cool really fast once the fan is turned on...at least in my experience. I have both my fans hook to the PCM low speed wire and have never needed anything else in this Texas heat.

[boostedc10]

What terminals are you using from the ECM?

If i remember right for single mode fan control you will use PIN 42 on the blue connector for fan 1 and PIN 33 on the red/green for fan2.

[jsett83]

I'm 99% certain the engine is reaching 210. The first fan kicks on and I continued to let the truck idle for an extended amount of time. I sent my harness out to have it cut down and it came back labeled with a green wire labeled main fan and a blue wire labeled aux fan. I believe the main fan relay is the one that is working. Not sure on what pins wires are coming from.

[Crash_OK]

Originally Posted by jsett83

I'm 99% certain the engine is reaching 210. The first fan kicks on and I continued to let the truck idle for an extended amount of time. I sent my harness out to have it cut down and it came back labeled with a green wire labeled main fan and a blue wire labeled aux fan. I believe the main fan relay is the one that is working. Not sure on what pins wires are coming from.

The second fan will not come on until the wire from the PCM goes to ground. My 5.3 has never got hot enough idling to kick in the high speed fan. It will if I have drove it for some time and then come to a stop.

[jsett83]

Interesting. My factory temp gauge does not seem to be too accurate,so was worried about not having both fans before driving. How long do you think I would have to drive to find out?

[Crash_OK]

Originally Posted by jsett83

Interesting. My factory temp gauge does not seem to be too accurate,so was worried about not having both fans before driving. How long do you think I would have to drive to find out?

I don't know... depends on a lot of variables. If you had a OBDII reader you most likely could get the water temp that the PCM is seeing. I have a scan gauge 2 that has that functionally.

[jsett83]

Good info, thanks! I will try to get my hands on a code reader.

[Houston Ben]

I also have the scanguageII for the RPM, MPH, Engine Temp and Air intake temp. Great tool for that. Look around for fan diagrams and you will find one with a 3 relay setup that will turn both fans on at low and high speed.

[Crash_OK]

this is what I did

[boostedc10]

Jsett by looking at your drawing you need both terminal 85's of your relays controlled by pin 42 of the ecm. This will make both of them come on at high speed. Crash's diagram is set up to run both high and low speed fan modes in which you would have to add a relay. Based on your drawing I am assuming you are only looking for one mode?

[aknovaman]

If you can set both fans to come on at 120 degrees in the PCM you can test your wiring for functionality. I prefer 200 and 205 for my fan settings. Higher and lower depending on how well they are shrouded and how well the engine bay breathes.

Once you know both are functional at 120 degrees, then you can set them up higher to their normal set points.

[ls1nova71]

Does kind of sound like fan 1 is cooling it enough that 2 isnt coming on. Try unhooking the first fan and see if the other one comes on.

[Gooker928]

My second fan never comes on at crank up idle no matter how long it sits.

[Crash_OK]

Originally Posted by Gooker928

My second fan never comes on at crank up idle no matter how long it sits.

Try ls1nova71 idea above..

"--------------------------------------------------------------------------------

Does kind of sound like fan 1 is cooling it enough that 2 isnt coming on. Try unhooking the first fan and see if the other one comes on. "

good luck