Nelson Harness problem with LS1 fans

[clayp]

I installed LS1 fans with a Nelson Harness into my 01 Silverado 5.3l today. Using a programmed PCM the fans work fine until the a/c wire is spliced in. I tapped into the dark green wire and checked the voltage - reads 8-10v when the a/c is on. When I connect the tap it causes the fans and the a/c compressor both to shut off. Is it possible that my harness has a bad relay?

[RedHeartbeat]

Have you tried to trigger the fans by using a direct connection of the lead that hooks to the a/c wire? If it's positive triggered, try to trigger the fans directly off the positive connection at the battery. If it's ground triggered, ground it and see if it works.

[farmtruc]

Sounds like the relay may be bad, possible shorting the a/c compressor.
Swap them around and see if something different happens.

sorry about that, whatever it is, we'll get it taken care of.


allen

[clayp]

Originally posted by farmtruc@Jan 7 2006, 09:43 PM
Sounds like the relay may be bad, possible shorting the a/c compressor.
Swap them around and see if something different happens.

sorry about that, whatever it is, we'll get it taken care of.


allen

Which relay is for the ac? I was thinking perhaps the wires into the relay are crossed or tied wrong.

[clayp]

Originally posted by RedHeartbeat@Jan 7 2006, 09:09 PM
Have you tried to trigger the fans by using a direct connection of the lead that hooks to the a/c wire? If it's positive triggered, try to trigger the fans directly off the positive connection at the battery. If it's ground triggered, ground it and see if it works.

Good suggestion - I will try that tomorrow. I am hoping that won't fry something though if the relay is bad or crossed.

[farmtruc]

Apply 12+volts to the green harness wire, it should turn the passenger fan on high.
Ground the blue pcm wire from the harness, it should turn both fans on low.
Doing both above will make both fans turn on high.

Let me know,

allen

[clayp]

Originally posted by farmtruc@Jan 7 2006, 10:13 PM
Apply 12+volts to the green harness wire, it should turn the passenger fan on high.
Ground the blue pcm wire from the harness, it should turn both fans on low.
Doing both above will make both fans turn on high.

Let me know,

allen

OK, when I connect the fan lead to the + of the battery the pass side fan comes on high. When the fan lead is disconnected, fans are off unless the temp raises and then fans then come on low. When I turn on the a/c, the fans engage (both) when the fan lead is DIS-connected. Connecting the fan lead shuts OFF the fans AND the a/c compressor.

[RedHeartbeat]

When both fans are running in low speed, if you connect the green lead from the harness to 12v power what does it do?

[clayp]

Originally posted by RedHeartbeat@Jan 7 2006, 11:19 PM
When both fans are running in low speed, if you connect the green lead from the harness to 12v power what does it do?

OK, When the fans are on low (they turn on low at temp and when I turn on the a/c, but only if the fan lead is disconnected) and then I touch the fan lead to the (+) the fans race to high speed.

So basically,

low fans:
1)activated by operating temp
2)activated by a/c turning on
3)both above only occur when the fan lead is disconnected altogether

high fans:
1)only turn on when touching fan lead directly to a 12v source

no fans, no a/c compressor:
1)when fan lead is connected to the dk green wire.
2)dk green wire reads 8-10v when a/c is activated and no fan lead connected
3)dk green wire reads 0v when a/c is activated and fan lead is connected

[RedHeartbeat]

sounds like you're connecting to the wrong a/c wire. The harness seems like it's working correctly if all works when you do touch the green to positive. All other indicators you describe sound correct except when hooking to the a/c green wire. Do you have a 12v test light? If you connect the test light to the green a/c wire and it does the same thing, no a/c, then you must have the wrong wire.