2003 E-fans troubleshooting help - SOLVED

[reedal]

I have a 2003 tahoe with an E-fan conversion done. OE equipment pulled from an 05 NBS a few years back, configured in HP tuners and everything has worked flawlessly for the last couple years until about a week ago.

E-fans no longer turn on. All three relays switch as intended in and out of the fuse box, no fuses blown either as I see 12vdc at both fan connectors when reading across the pins with vehicle running. I hear the relays actuate when turning on using VCM scanner, but the fans still don't turn on. Fans spin wonderfully when bypassing the circuitry and are straight wired to a 12v source so the fans aren't dead.

I'm at a loss and can't figure out what i'm missing. It can't be the PCM or VCM wouldn't actuate the relays, can't be fuses or relays or i wouldnt see the 12-14vdc with the key on. That specifically tells me it would be the fan motors, but the fans spin when directly connected to the battery.

Everything is configured exactly as the OE wiring diagram shows. My ground is directly connected to the battery negative, and i put a new ring terminal on and tested it at different locations with no change.

 

[Fless]

Voltage in and of itself means almost nothing. If your voltmeter reads 12v across the fan connector contacts -- not using a separate ground to measure -- but the fans don't run, I would suspect a faulty ground or a compromised 12v wire that can't handle the load. Or a defective relay. Have you tried new relays?

You could also test the fan voltage on the closed circuit, with the fans connected, to see what it is when loaded.

 

[justirv]

I have a 2003 tahoe with an E-fan conversion done. OE equipment pulled from an 05 NBS a few years back, configured in HP tuners and everything has worked flawlessly for the last couple years until about a week ago.

E-fans no longer turn on. All three relays switch as intended in and out of the fuse box, no fuses blown either as I see 12vdc at both fan connectors when reading across the pins with vehicle running. I hear the relays actuate when turning on using VCM scanner, but the fans still don't turn on. Fans spin wonderfully when bypassing the circuitry and are straight wired to a 12v source so the fans aren't dead.

I'm at a loss and can't figure out what i'm missing. It can't be the PCM or VCM wouldn't actuate the relays, can't be fuses or relays or i wouldnt see the 12-14vdc with the key on. That specifically tells me it would be the fan motors, but the fans spin when directly connected to the battery.

Everything is configured exactly as the OE wiring diagram shows. My ground is directly connected to the battery negative, and i put a new ring terminal on and tested it at different locations with no change.

What @Fless said... Check the ground being supplied. Connect your volt meter to batt +12v, then the other lead to the "negative" pin on the fan connector, if you have anything but a solid +12vdc there, check where your relay/fan housing is grounded. Could be a dirty/bad connection or even corrosion internal in the wire.

 

[Fless]

The voltage test I noted needs to be done with the circuit loaded -- fans connected and (known to be) commanded on.

 

[reedal]

I appreciate the feedback.

Turns out the OE splice for the ground failed (no visible indication as to why) where the fan connector grounds meet the ground wire and continues to socket 87 (A1) for relay #3. There was about 1.5kohm resistance between my crimped ring terminal and the socket, but when measuring before the splice the ring terminal wire was good.

Cut, solder, and heat shrink the three wires back together and its good to go now, fully functional at low and high speed setpoints

 

[Fless]

Nice work!

One thing I'll add is that a 4A or hefty test light fixture would be invaluable when load testing circuits like this. Yes, that test load should roughly match the normal load, but something like a couple of brake light bulbs wired up as a test jig would show if the circuit can handle the load.

EDIT: am I reading it correctly that G115 was the compromised ground? Where exactly is it?

 

[reedal]

Yes, the G115 wiring. The OE splice is about 6 inches down from the socket that relay #3 pin 87 sits in. I maybe lost an inch in total wire length combined between cutting all three to redo the splice, but there's still plenty of slack in the wires that go to the battery and the fan.

 

[justirv]

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Yes, the G115 wiring. The OE splice is about 6 inches down from the socket that relay #3 pin 87 sits in. I maybe lost an inch in total wire length combined between cutting all three to redo the splice, but there's still plenty of slack in the wires that go to the battery and the fan.

Thanks for the update and details on what you found.