Electric Fan Conversion Question

[Dantheman-2003]

I’m in the process of electric fan conversion on my 03 Tahoe. I pulled the factory harness off my 05 Yukon. From what I can tell, I have thick blue/black and yellow/grey wires going to fans. Red for power. The 2 small wires blue and green go to PCM pins.

Question is, where is the black ground wire that bolts to frame? I never saw one as I was removing this.

Any thoughts would be appreciated!

 

[Sam Harris]

I’m in the process of electric fan conversion on my 03 Tahoe. I pulled the factory harness off my 05 Yukon. From what I can tell, I have thick blue/black and yellow/grey going to fans. Red for power. The 2 small wires blue and green goes to PCM pins.

Question is, where is the black ground wire that bolts to frame? I never saw one as I was removing this.

Any thoughts would be appreciated!

IIRC, that ground fit nicely to an existing ground pin right near the fuse box. It was fairly obvious, once I had my harness in its rough-in location. Also, if you haven’t already got one, I picked up a new fuse box with the additional relay spaces & cover on eBay for a really reasonable price. I think it was around $20-$25..

 

[Dantheman-2003]

IIRC, that ground fit nicely to an existing ground pin right near the fuse box. It was fairly obvious, once I had my harness in its rough-in location. Also, if you haven’t already got one, I picked up a new fuse box with the additional relay spaces & cover on eBay for a really reasonable price. I think it was around $20-$25..

Guess my question is, where does the ground wire connect to my harness? All the aftermarket kits I see include a red power and black ground that connects to a grounding location. My factory harness does not have a separate black ground wire. The only black I see goes to the fan.

 

[Sam Harris]

Ah, apologies, I didn’t realize what you said the first time. That’s odd. Mine has a double wire ground, you can see in this picture, when I was wiring it up, it’s attached to the front accessory bracket.

 

[Fless]

Ah, apologies, I didn’t realize what you said the first time. That’s odd. Mine has a double wire ground, you can see in this picture, when I was wiring it up, it’s attached to the front accessory bracket. View attachment 393241

The one in the green triangle, right @Sam Harris?

 

[ncalvo]

Ah, apologies, I didn’t realize what you said the first time. That’s odd. Mine has a double wire ground, you can see in this picture, when I was wiring it up, it’s attached to the front accessory bracket. View attachment 393241

Doing my efans soon, I have an oem harness, where did you put your fuse box?

 

[mattbta]

15215145 is the fuse box cover with accommodation for the OEM fan harness. Lift the main one up and slide the fan one in next to it on the right if you’re looking at it from the DS fender. You’ll see the area the circular part fits over. The non e-fan cover will fit over the harness, you just won’t have fuse or relay access without taking the whole thing out. This has a small removable piece on top.


Haven’t had any luck finding a pic of where the grounds come out of the OEM harness, yet. Tried to find a view on my old GMSI but no dice. Someone should be able to find a wiring diagram for that box, though.

 

[Tonyrodz]

@ScottyBoy is the electric fan expert. Lots of guys--including me--bought cleaned up OEM harnesses from him. Hopefully he'll share some knowledge here.

 

[ScottyBoy]

Yes, there should be a double ground wire on the OEM harness. It's a ring terminal with TWO ground wires on it, one of those leads up to the relay/fuse block, and the second wire goes directly to the plug for fan #2. That plug has a blue and black, the other fan has gray and yellow wires. From the factory, the ring terminal is grounded to the frame on the passenger side, in the area right behind the bumper bracket. I grounded mine in the same area. I just attached mine to the bolt that holds the horn bracket to the frame right there on the passenger side frame rail.
It appears that you cut the harness just below the fans, that explains why you are missing the rest of the ground wire. You only have one wire connected to your relay/fuse block now. The other half of that wire, and the ground for fan #2 were cut off .

 

[Fless]

Looks something like this:

 

[Dantheman-2003]

Yes, there should be a double ground wire on the OEM harness. It's a ring terminal with TWO ground wires on it, one of those leads up to the relay/fuse block, and the second wire goes directly to the plug for fan #2. That plug has a blue and black, the other fan has gray and yellow wires. From the factory, the ring terminal is grounded to the frame on the passenger side, in the area right behind the bumper bracket. I grounded mine in the same area. I just attached mine to the bolt that holds the horn bracket to the frame right there on the passenger side frame rail.
It appears that you cut the harness just below the fans, that explains why you are missing the rest of the ground wire. You only have one wire connected to your relay/fuse block now. The other half of that wire, and the ground for fan #2 were cut off .

Yes correct. That’s exactly what happened. I hacked it outta that Yukon right before it was towed away. Time was of the essence.
So question is now, do I just junk this hacked up OEM harness and purchase a kit on eBay? Or is there a way to add a ground to the relay/fuse box, then connect to the frame?

 

[Dantheman-2003]

Yes, there should be a double ground wire on the OEM harness. It's a ring terminal with TWO ground wires on it, one of those leads up to the relay/fuse block, and the second wire goes directly to the plug for fan #2. That plug has a blue and black, the other fan has gray and yellow wires. From the factory, the ring terminal is grounded to the frame on the passenger side, in the area right behind the bumper bracket. I grounded mine in the same area. I just attached mine to the bolt that holds the horn bracket to the frame right there on the passenger side frame rail.
It appears that you cut the harness just below the fans, that explains why you are missing the rest of the ground wire. You only have one wire connected to your relay/fuse block now. The other half of that wire, and the ground for fan #2 were cut off .

Also, I looked everywhere. I never saw a double ground anywhere. Appreciate the feedback.

 

[Sam Harris]

The one in the green triangle, right @Sam Harris?

View attachment 393242

Yessir. Thank you @Fless

 

[ncalvo]

15215145 is the fuse box cover with accommodation for the OEM fan harness. Lift the main one up and slide the fan one in next to it on the right if you’re looking at it from the DS fender. You’ll see the area the circular part fits over. The non e-fan cover will fit over the harness, you just won’t have fuse or relay access without taking the whole thing out. This has a small removable piece on top.


Haven’t had any luck finding a pic of where the grounds come out of the OEM harness, yet. Tried to find a view on my old GMSI but no dice. Someone should be able to find a wiring diagram for that box, though.

Awesome, thank you for that part number, just what I was looking for found it on ebay for $28

 

[Sam Harris]

Doing my efans soon, I have an oem harness, where did you put your fuse box?

I bought mine on eBay. It was NIB, GM & just over $20 shipped. Unfortunately, looking again the other day, I didn’t find any. Might have to source it elsewhere. I was also looking for the p/n, and couldn’t find it. I still have the original in the box it came in. I’ll check for the p/n on that box..

ETA: @mattbta beat me to it.

 

[Dantheman-2003]

Ah, apologies, I didn’t realize what you said the first time. That’s odd. Mine has a double wire ground, you can see in this picture, when I was wiring it up, it’s attached to the front accessory bracket. View attachment 393241

Where do your 2 grounds trace back to on the harness?

 

[ScottyBoy]

Where do your 2 grounds trace back to on the harness?

The double wire ground on the 05+ trucks is a ring terminal attached to the factory side frame rail just above the passenger side frame horn/bumper bracket. It's difficult to see it unless you are specifically looking for it.
I attached mine in the same general area. I grounded it to the bolt that holds the horn to the passenger side frame. And you know that's a good ground because the horn is grounded through that same bolt.

 

[mattbta]

This eBay link has a shot of the underside of the relay/fuse box. https://www.ebay.com/itm/266158322851

Hope this helps.

 

[Sam Harris]

The double wire ground on the 05+ trucks is a ring terminal attached to the factory side frame rail just above the passenger side frame horn/bumper bracket. It's difficult to see it unless you are specifically looking for it.
I attached mine in the same general area. I grounded it to the bolt that holds the horn to the passenger side frame. And you know that's a good ground because the horn is grounded through that same bolt.

Thanks for this. I’ll move mine next time I’m doing some work on her.

 

[mattbta]

Thanks for this. I’ll move mine next time I’m doing some work on her.

Yeah, I tried to use the original/factory spot on mine with a bolt i forced in, but it didn't work (fans wouldn't turn on), so for now I punted and put it on the same spot driver side where two other grounds are. Now to either buy a proper bolt for the factory location or use this spot @ScottyBoy mentioned since I didn't reduce the length of the ground wires. Thanks.