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Electric fan wiring

AVArookie

Full Member
Joined
Sep 6, 2010
Messages
240
Location
Mi., AFG, Georgia
I did a search here to find an answer before asking, but, all I could find was topics concerning the aftermarket wiring, and pin 42. I bought a set of stock 2005 Silverado fans and wiring harness. Does anyone know where the correct ECU pins go to? I have looked on line and seen a few different harness diagrams, but not sure witch one is correct.

When looking at the harness, I figure the power, and ground lead ring terminals should go to the power distribution block on the left side of the block, the ground will go to a good grounding point. Then I need to find out where to put the two wires that go to the ECU. The rest is just plug and play...

Which one is correct, if either? I'm thinking the first one.
ls1coolingfansbu6.gif


Y2KMalibucoolingfan.gif


 
Nelson has a three relay harness that has low and high speed control and makes for a pretty clean install...

Pins #42  and I think the other is #31 and will have to be programed to work correctly.. Talk to Nelson..


http://www.nelsonperformance.com/


http://www.nelsonperformance.com/fan-harness

 
Once again, you did not take the time to read the post clearly. Please do not respond to my posts, you just make a mess of them. Regards...
 
Randy said:
Nelson has a three relay harness that has low and high speed control and makes for a pretty clean install...

Pins #42  and I think the other is #31 and will have to be programed to work correctly.. Talk to Nelson..


http://www.nelsonperformance.com/


http://www.nelsonperformance.com/fan-harness

It's pins 33 and 42 not 31 and 42 as you claim. No matter how many times you try to edit your posts to make you look like you know what you are talking about, please do not respond to my topics/posts.

Not only did you add the info about the pins, you deleted the Black Bear link from your original post. I don't want future readers getting the wrong info or ideas from someone who gives out the wrong information. A quick check on your post history, and checking the dates and times of edits of your posts will clear things up.

I am aware of the programming, I have a personal tuner that has me covered...
 
All concerned, lets keep the posts on track so they benefit all.
 
I used the Nelson harness in my 03 so my experience may not be what you are looking for but pin 42 sure sounds familiar.

One thing to note is that Nelson's harness is set up to have 3 fan running modes of operation - these diagrams appear to offer two.  Main difference is that Nelson's runs the passenger side fan whenever the AC compressor is running to blow warm air over it and possibly as well to be pulling some air through the condenser.  Unlike the programming in my 2000 vette, the 03 Avalanche computer program doesn't offer any settings available to me (via HPTuners) to turn on the fans based on AC.  Nelson's harness does that by tapping into the AC clutch signal.

Since you are running the 6.0, I'll also note here that my 6.0 runs hotter than the 5.3.  I've often wondered if I should do a tweak to how the Nelson harness operates as it only runs both fans at high speed when the AC compressor is running.  That said I've got it set to run the fans when I shut down the engine if the coolant temp is at or above 199 and I've only heard them running at engine shutoff once this summer.  It just so happened that I had been data logging at the time - coolant temp was right at 199.  (I've got the fans set to come on at 189 - turn off at 183.)

If no one else is able to more directly answer your question I'll take a look this evening at my GM service manual's pinouts for the PCM's connectors.
 
enoniam said:
I used the Nelson harness in my 03 so my experience may not be what you are looking for but pin 42 sure sounds familiar.

One thing to note is that Nelson's harness is set up to have 3 fan running modes of operation - these diagrams appear to offer two.  Main difference is that Nelson's runs the passenger side fan whenever the AC compressor is running to blow warm air over it and possibly as well to be pulling some air through the condenser.  Unlike the programming in my 2000 vette, the 03 Avalanche computer program doesn't offer any settings available to me (via HPTuners) to turn on the fans based on AC.  Nelson's harness does that by tapping into the AC clutch signal.

Since you are running the 6.0, I'll also note here that my 6.0 runs hotter than the 5.3.  I've often wondered if I should do a tweak to how the Nelson harness operates as it only runs both fans at high speed when the AC compressor is running.  That said I've got it set to run the fans when I shut down the engine if the coolant temp is at or above 199 and I've only heard them running at engine shutoff once this summer.  It just so happened that I had been data logging at the time - coolant temp was right at 199.  (I've got the fans set to come on at 189 - turn off at 183.)

If no one else is able to more directly answer your question I'll take a look this evening at my GM service manual's pinouts for the PCM's connectors.

1) Agreed, this is a GM harness diagram, so yes, only two fan mode. Did not know about the three fan mode that Nelson offers, how does it work exactly?
2) We also use HP tuners as well, so the information you gave is good to know as well. With Nelson, do they have to do the programming?
3) I like the idea of the fans running after shut down, I have done that before on a previous vehicle.
4) I have the pin outs now, Green wire lands in pin 42 of the blue connector. The blue wire goes on pin 33 on the green connector.

I was hoping to run this as stock as possible, but, I know Nelson Performance has a great reputation as well.

And thank you for your information,
Regards.
 
AVArookie said:
1) Agreed, this is a GM harness diagram, so yes, only two fan mode. Did not know about the three fan mode that Nelson offers, how does it work exactly?
2) We also use HP tuners as well, so the information you gave is good to know as well. With Nelson, do they have to do the programming?
3) I like the idea of the fans running after shut down, I have done that before on a previous vehicle.
4) I have the pin outs now, Green wire lands in pin 42 of the blue connector. The blue wire goes on pin 33 on the green connector.

I was hoping to run this as stock as possible, but, I know Nelson Performance has a great reputation as well.

And thank you for your information,
Regards.

Answer to 1) - Both fans run at low speed without AC compressor running / both run at high speed with AC compressor, when above the "Fan 1" parameters set via HPTuners.  Below that without AC no fans run / with AC passenger side runs at high speed.
2) - I do all the tuning myself.
3) - Easily set via HPTuners.
4) - Glad you got the correct pins to use.

Note that above answers are for my stock 03 Avalanche PCM and program using reprogrammed data parameters.

One downside to my Nelson harness is that I need to replace at least one relay every year it seems.  (Ask Hugz what it's like when you replace one with a bad one out of the box from the auto parts store.  :E:)
 
I don't know of a downside to running the stock 05 harness and fans other than not having any airflow across the compressor when running.  It's interesting to me that in my '00 vette's stock PCM and programming that they include parameters for different operation based upon AC status but GM didn't include that in the trucks' programming.  Maybe since at the time they were't putting the efans into the trucks that was something that wasn't fully cooked in the programming.

I didn't consider using a stock harness when I did mine many years ago.  Since you've got one I'd say go ahead and see what it does.  The worst thing I suppose is that your AC may not work as well - you can always replace with a Nelson or other harness later in that case.

By the way the Nelson harness uses 3 relays.  One could probably make a few wiring changes to the 3 relays shown in your diagrams to get the same functionality as what the Nelson harness has.
 
Answer to 1) - Both fans run at low speed without AC compressor running (got it) / both run at high speed with AC compressor, when above the "Fan 1" parameters set via HPTuners (understood).  Below that without AC no fans run (why don't the fans turn on?)/ with AC passenger side runs at high speed (I'm a little unclear on this, I thought they both come on high with A/C). Is there ever a time only one fan is engaged?



I was planning on running the stock one and see how it does, and yes, I could always tap in another relay to make them run from the A/C like the Nelson.
Thanks again for you information. Hopefully this will help others in the future.
 
AVArookie said:
Answer to 1) - Both fans run at low speed without AC compressor running (got it) / both run at high speed with AC compressor, when above the "Fan 1" parameters set via HPTuners (understood).  Below that without AC no fans run (why don't the fans turn on?)/ with AC passenger side runs at high speed (I'm a little unclear on this, I thought they both come on high with A/C). Is there ever a time only one fan is engaged?

It's confusing when described in words - better to put it into a chart format:

                              No AC                              AC
Low Temp              no fans                    passenger side on high
High Temp        both fans on low              both fans on high
 
AVArookie said:
I still have my stock '03 computer as well. In your opinion, what are the down sides to running the stock '05 harness and fans?
None. I did the mod on my '04. I had Monte put together a tune for the truck and also set the fans to work through the pins. Roughly 5 years and never had an issue with them.
 
Found some information that states my stock 2003 ecu controls the fans from coolant temp and a/c pressure.

Your truck is an 03 so you have the same pcm the 05 trucks use. You hook it up as per the oem 05 and newer setup. Your pcm can control based on a/c system pressure whereas the older trucks cannot.
 
AVArookie said:
Found some information that states my stock 2003 ecu controls the fans from coolant temp and a/c pressure.

Your truck is an 03 so you have the same pcm the 05 trucks use. You hook it up as per the oem 05 and newer setup. Your pcm can control based on a/c system pressure whereas the older trucks cannot.

Interesting.  I wonder why Nelson would make a harness that taps into the AC compressor clutch control line if it could all have been done through the computer.  ???
 
Well, I wired as much as I could yesterday, all except for the ground. My tuner and I are on different schedules for a while, so when we can meet up again, all I have to do is drop in the fans, and ground, then tune. I'll post back up when it is finished. Thanks for all the help...
 
Fans are in, bad trans out, new one in, all tuning complete. So far the positive claims that were made of what I would gain by going electric are true. A/C is definitely colder, not by a little, but a very noticeable amount. No more clutch fan noise, can't explain the noise it used to make from sucking the air through it. Between the new fans and tires, it's like driving a new truck, with great NVH qualities.

Oh, and by the way, if you have a K&N air filter, GET RID OF IT! Smoked my trans because of it, no B.S., I have a tuner and numbers that will back up this claim. It was my trans builders first question when I called him to get a trans ready for me, "do you have a K&N air filter?" Now I am running a stock WIX filter, the MAF numbers show the difference.

Thanks to one and all for the information and suggestions...
 
HOW does an air filter ruin a Transmission?
 
Trans is controlled through the MAF, when the MAF is not reading correcting, it seems corrupt information in effect to the trans. If you over oil the filter, it can sucked onto the MAF, causing bad readings, same goes in the opposite direction. K&N filters have also been known to contaminate your engineer oil as well.
 
then your statement about the AIR fitler ruining the tranny is incorrect

YOu meant an OVER OIL FILTER can damage Tranny

Many threads on this and even a TSB from GM on this issue of over oil MAF.
 
Look in to a filter that is under pulled as well, it's not just from over oiling, or from "correctly oiling" so yes, I still stand by what I originally wrote.
 
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