Nelson LS1 Fan Harness Problem

Ok here is the situation...

*R/L from drivers seat perspective*
AC Off/ Truck not at operating temp (Both Fans Off)
AC On/ Truck not at operating temp (R Fan on High, L Fan off)
AC Off/ Truck at operating temp (Both Fans Off) <--Very Bad
AC Off/ Truck at operating temp (R Fan on High,L Fan off) [The left fan will sometimes seemingly turn on low, seems that it happens some times and not others]

Put connection from R Fan to L Fan and turned on truck and AC and L Fan ran on high. So I know that both fans work. When I received the Kit one relay was damaged so I replaced it with one that I had. Do you know of any way I could test relays to see if they are operating properly? Is there anyway I could have installed the blue wire wrong (it snapped into place when installing seems pretty fool proof) and I am sure I am connected to the right green AC wire (since that is the only thing that is working properly).

Thanks guys, was sitting in the staging lanes tonight and my truck almost over heated on me. Got 2 runs in and the truck only ran 2 tenths faster (This is after a tune LT headers e-fans) very disappointing night.

Did you double check it was on pin 42 on the blue Ecm connector, if it is maybe the tune did not go through, because if the a/c part works good, and the engine side doesn''t it has to be the blue wire signal, try splicing the blue wire to battery voltage, first unplug the blue connector from the ECU, when you do that both fans should turn on low...

Thanks, will check tomorrow morning. if I accidentally put it in the wrong pin hole how do I go about getting it out?

Take the blue cover off the connector, then you can release a small lock tab between the pin and connector, and pull on the wire from the back side out...

Have you had the PCM pin turned on in your tune to make the fans operate with temperature? You have to have that done by a tuner, it won't do it on its own.

PCM wire is connected in 42 and yes I had Nelson do a retune when I got the e-fans

So it must be Bad relays or a bad tune... I'm sure Nelson didn't mess up on wiring it :)

Do not touch the blue wire to positive voltage it is a ground .
The PCM acts as ground to activate fans .
And not all relays are the same even thought they may have the same pin design .

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Originally Posted by use2bfo

Do not touch the blue wire to positive voltage it is a ground .
The PCM acts as ground to activate fans .
And not all relays are the same even thought they may have the same pin design .

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+1

Well I rotated all the Relays around and every time the AC fan still worked as its supposed to, so I suppose the tune didn't go through. I'm sure Nelson is closed today, so i will give them a call tomorrow

Ooops.

Had a little problem with mine yesterday too. This example was the fault of the installer (*cough*). AC started blowing hot then got the engine coolant hot message....dummy mechanic didn't properly tighten the fan grounds....

Talked to Nelson a while back and concluded that all the relays are in working order and the tune is correct. Started looking into the wiring...

I can't make heads or tails of anything wrong so i drew up the diagram for it based on what my harness looks like. Does anyone notice anything wrong? All the connections look good.

http://i51.photobucket.com/albums/f3...-Harness-1.jpg

sounds to me like the new pin u put in the pcm isnt making good contact....i had to take the actual blue cover off mine and pull it through instead of pushing from the back

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Originally Posted by banker099

sounds to me like the new pin u put in the pcm isnt making good contact....i had to take the actual blue cover off mine and pull it through instead of pushing from the back

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+1

Yeah, take the blue cover off and you need to push it in all the way... Haha, that's what she said!!! Anyway, with the blue cover off, you should be able to see how far all of the other pins were pushed. Make sure it is seated correctly.

its seated correctly. If you take it out and ground it directly to the battery the relay clicks but the fan doesn't turn on. and I know the fan is working as well

Was going to call Nelson today but this hurricane is putting a damper on things

Okay, I'm not genius on any of this but I noticed something weird in your diagram and thought I would bring it up. On relays 1 and 2 you have the power (+) going to the 87 terminal and return (-) going to the 86 terminal. It's different on relay 3, i.e. reversed. I'm not sure if this amounts to a hill of beans but thought I would mention it. It seems like the left fan is not getting power (from your explanation) and running the power through your diagram is where I saw the above explanation.

Yeah--but another question for you concerning the wiring diagram--how come you are running 3 relays? And why are you wiring a relay to the A/C?

I would have 2 relays, one for each fan. I would also include 2 in-line 30 amp fuses, one for each fan. Don't even worry about wiring anything to the A/C. That is done by the PCM.

nelsons harness comes with 3 relays so the fans will run on low and high, along with one at a time, and both on at the same time

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Originally Posted by banker099

nelsons harness comes with 3 relays so the fans will run on low and high, along with one at a time, and both on at the same time

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+1

I think Jon is working with you on this, he took pics and will send them to you so you can compare the wiring with a harness here.

jon@nelsonperformance.com


let us know,
allen

The only thing I don't like about this design is it cycles fans with A/C compressor on and off . Good for the little tiny fans from a LS1 but not for the big fans of a 05 .
There is no reason a PCM can't be set up to run the pins 33 and 42 correctly and use the correct harness design . :twocents:

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Originally Posted by use2bfo

There is no reason a PCM can't be set up to run the pins 33 and 42 correctly and use the correct harness design . :twocents:

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Yes there is, (with this harness), on some truck pinouts that pin is already taken, I can't remember exactly what its connected to, but you can't tap into it or replace it.
On some trucks you can use the pcm for the a/c, however, the pcm needs to support that, like on an fbody or like the '05+ trucks are setup.

I'm sure a harness can be designed to work with anything, but not with this setup/harness (what he has). So, that's what we have to fix.

Oh, I just looked it, pin33 "recirculation door control", can't use it!

Recirc door control on what? No truck. PCM control of the recirc door? Wow...not sure the application.

Anyway,,,,my giant single Flex-a-lite on the Blazer cycles with the compressor as well and is fine.....and loud.

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Originally Posted by GasGuzzler

Recirc door control on what? No truck. PCM control of the recirc door? Wow...not sure the application.

Anyway,,,,my giant single Flex-a-lite on the Blazer cycles with the compressor as well and is fine.....and loud.

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I have no idea either, but I tried this pin one time and the fan barely moves, kind of an on and off motion. Like the relay is triggering, then off, then on.

I'd be interested as well in a new fan harness for the pre 04 trucks, but the fans have to come on with the compressor.

My harness does that but it takes 4 relays and you have to tie into the power lead to the A/C clutch. It has all the controls the factory setup has with the dual PCM control leads.

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Originally Posted by RedHeartbeat

My harness does that but it takes 4 relays and you have to tie into the power lead to the A/C clutch. It has all the controls the factory setup has with the dual PCM control leads.

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Ya, the fbody pcm is much nicer and actually has values you can change in the pcm.

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Originally Posted by farmtruc

Yes there is, (with this harness), on some truck pinouts that pin is already taken, I can't remember exactly what its connected to, but you can't tap into it or replace it.
On some trucks you can use the pcm for the a/c, however, the pcm needs to support that, like on an fbody or like the '05+ trucks are setup.

I'm sure a harness can be designed to work with anything, but not with this setup/harness (what he has). So, that's what we have to fix.

Oh, I just looked it, pin33 "recirculation door control", can't use it!

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As Red said 4 relays can do it .
Perhaps I look at things differently than that , I think 2002 up can be wired to use 33 and 42 , some use pin 16 for fans (red connector , green 33) . Can you look at pin 16 and see if it will work ?
Funny that pin 33 will not work in some , cause all you need is PCM to ground the wire , can a segment swap be done with just the needed fan parameters ?
I agree that fans need to be on when A/C pressure reaches critical pressure , keeps it from going boom .

2003 Blue connector 33 is TCC Brake Switch/Cruise Control Release Switch Signal. Green 33 is not used in 2003 but there are some 20-25 unused pins.

I looked back to 2000 and found Green 33 to be as Allen said, "HVAC Recirculation Door Control"....

Looking forward I see that it's like that to 2002. I would guess it's because the 2003+ have a Class2 HVAC control head that controls the recirc itself.

Does that mean a 2003-2004 can use the empty Green 33? Not sure. You can't just make any empty pin live can you?

So 1999-2002 Green 33 is taken but 2003-2004 Green 33 is empty. 2005-2006 Green 33 is used for fan operation.

Now I see why people are mentioning Green 33. It's the fact the 05-06 uses this for high speed operation. Instead of high right side with compressor on (like the Nelson harness), the PCM can command high fans (both) when AC high side pressure crests 265 psi.

In the end it's six of one, half a dozen of the other. With the LH fan on low and the RH fan on high (like with the Nelson harness), I doubt the high side AC pressure would ever get too high. The blow off valve in the compressor opens between 425-440 psi.

If it would help, I could list all the empty pins for 2003-2004....but once again, I'm not sure if just any pin can be made to carry out certain functions.

What is the internal design difference between the 03-04 PCM and the 05-06?

If a fan that ran is a ran fan then a ran fan is a fan ! :doofus:

With the PCMs, the PIN slot receives a signal from the sensor it is wired to, and then carries out that required function. Like with the fans, all the PCM does is ground the fan's circuit. Nothing else. It is already hard wired to receive power. The PCM tells its self (from the water temp sensor) how warm the motor is, and grounds the fans to complete the electrical circuit. So, with that said, I doubt you would be able to use an empty PIN location to operate a required function.

In order to get the PIN to operate correctly, one would have to have PCM editing software that could program what the exact PIN location needs to do, e.g. what it needs to rely on by other sensors to make it's function happen. For example, to get the fans to come on when the A/C is engaged, the PCM would have to receive a signal from the A/C fan clutch--then know to ground the circuit for the fans to come on at 100&#37;. Or once the climate control button has been pressed to engage the A/C, the A/C clutch is activated---and that electrical circuit is completed...and the wiring for the fans is bridged to it, so that is how they come on?? I really don't know how GM decided how to wire everything up. I bet they just thought that they needed (lets just say for grins) 50 PIN locations. You just don't go out and make a PCM to accomodate 50 pins...you make one with like 60 slots--to make sure you CYA if you ever have to go back and alter the wiring. I could be wrong on all of this, but I would imagine that our PCM's tuning software (HPT, LS1EDIT, EFILive) can only modify/edit what PCM functions are available--not program empty PIN slots...