Electric Fan Conversion Question

[Dantheman-2003]

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.

Appreciate the feedback. I get that the ground or grounds are to be fastened to a grounding source such as the frame. My question is, going back the other direction, where is the ground starting point at fuse block? As I’ve mentioned, I have 1 black ground coming out of the fuse block and eventually makes its way to one of the fans. Are you saying tap this black ground and pigtail off to a grounding point?

 

[Rocket Man]

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?

Do not buy an aftermarket harness unless you enjoy melted wires on a hot day. Fix up that factory harness.

 

[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 .

I think you answered my question here. All I need to do is tap the black wire coming from the fuse block and route a separate run to a grounding source.

 

[ScottyBoy]

Appreciate the feedback. I get that the ground or grounds are to be fastened to a grounding source such as the frame. My question is, going back the other direction, where is the ground starting point at fuse block? As I’ve mentioned, I have 1 black ground coming out of the fuse block and eventually makes its way to one of the fans. Are you saying tap this black ground and pigtail off to a grounding point?

Correct. That ground needs to be connect to the frame/grounding point. The second pin on the first fan also needs to be grounded, that fan plug should have the light blue wire and a black ground wire. The other fan is fed by the yellow and gray wires.

I was in the junkyard yesterday removing a harness and I got a pic for you of where the factory ground point is for the fan harness on the 05-06 trucks. It's not easy to find (or see) unless you are specifically looking for it. It's basically hidden behind the bumper. It's on the passenger side frame, just below the radiator support, right behind the bumper.

 

[mattbta]

Correct. That ground needs to be connect to the frame/grounding point. The second pin on the first fan also needs to be grounded, that fan plug should have the light blue wire and a black ground wire. The other fan is fed by the yellow and gray wires.

I was in the junkyard yesterday removing a harness and I got a pic for you of where the factory ground point is for the fan harness on the 05-06 trucks. It's not easy to find (or see) unless you are specifically looking for it. It's basically hidden behind the bumper. It's on the passenger side frame, just below the radiator support, right behind the bumper.

When you say first fan is black/blue and other is yellow/gray - do you mean first fan = driver side?

 

[ScottyBoy]

When you say first fan is black/blue and other is yellow/gray - do you mean first fan = driver side?

I honestly can't remember which is which as far as left or right. But I know for a FACT that one fan is black and blue, and the other fan is yellow and gray. To be honest, I'm not really sure it even matters to be honest which fan is left or right. But the wire colors on each plug DO matter. If you don't have the fan pigtails, I can check for you to see which actual pin is each color on each plug.

 

[mattbta]

I honestly can't remember which is which as far as left or right. But I know for a FACT that one fan is black and blue, and the other fan is yellow and gray. To be honest, I'm not really sure it even matters to be honest. If you don't have the fan pigtails, I can check for you to see which actual pin is each color on each plug.

I have the full harness, just didn't know which one went to which. You're right, probably doesn't matter. (I'm not OP)

 

[Dantheman-2003]

Correct. That ground needs to be connect to the frame/grounding point. The second pin on the first fan also needs to be grounded, that fan plug should have the light blue wire and a black ground wire. The other fan is fed by the yellow and gray wires.

I was in the junkyard yesterday removing a harness and I got a pic for you of where the factory ground point is for the fan harness on the 05-06 trucks. It's not easy to find (or see) unless you are specifically looking for it. It's basically hidden behind the bumper. It's on the passenger side frame, just below the radiator support, right behind the bumper.Thanks for the effort and explanation.

Correct. That ground needs to be connect to the frame/grounding point. The second pin on the first fan also needs to be grounded, that fan plug should have the light blue wire and a black ground wire. The other fan is fed by the yellow and gray wires.

I was in the junkyard yesterday removing a harness and I got a pic for you of where the factory ground point is for the fan harness on the 05-06 trucks. It's not easy to find (or see) unless you are specifically looking for it. It's basically hidden behind the bumper. It's on the passenger side frame, just below the radiator support, right behind the bumper.

Thanks for the effort here I do appreciate it greatly. My only variance to what your saying is, my black and blue goes to the passenger side fan, which I would consider the second fan. Correct me if im wrong. Now, the way I see it there is one black ground coming from the fuse block. That wire needs to connect to the frame (or alternate ground point) then splice off and connect to the fan port. Which in my situation goes to the fan on the passenger side of the truck. Is this right?

 

[Dantheman-2003]

Thanks to all and especially @ScottyBoy. Dang, we beat this one to death huh? On to the next project!

 

[ScottyBoy]

Thanks for the effort here I do appreciate it greatly. My only variance to what your saying is, my black and blue goes to the passenger side fan, which I would consider the second fan. Correct me if im wrong. Now, the way I see it there is one black ground coming from the fuse block. That wire needs to connect to the frame (or alternate ground point) then splice off and connect to the fan port. Which in my situation goes to the fan on the passenger side of the truck. Is this right?

Technically, that ground isn't coming FROM the fuse block, it's going TO the fuse block. As it's wired stock, it's two ground wires, attached to the same ground/ring terminal. One wire runs directly from that ring terminal to the passenger side fan (black and blue plug) and the other ground wire goes directly to the fan relay block/fuse block. The relays are what switches it to send ground to the other fan (gray and yellow plug).
So in a nutshell, you just need a good ground wire ran to the black wire on the relay/fuse block and to the black wire on the second fan plug. If you want to run two separate grounds with two separate ring terminals, that will be perfectly fine so long as EACH one is firmly bolted to the engine block or to the frame.

 

[Jkpii2000]

@ScottyBoy you seem to be very knowledgeable on these fan swaps! I did this conversion about 3 years ago on my 03 Tahoe. My fans run all of the time (driving down the road and in winter on cold start ups). All factory parts came from a junkyard 05 Tahoe. Install was very straightforward annd simple until I pinned the ecm plug. I sent my ecm into a guy named Jesse that specializes in the fan swaps (everyone online swears by this guy). I can get more info on him if needed. He now owns a business and does a lot of different programming. I installed my programmed ecm and the fan run constantly. I switched the ecm pins and still runs consistently. I changed all relays and fuses in the factory fuse box purchased on eBay and no difference. I believe it’s a programming issue so I contacted Jesse. He assured me it’s not programming. So my question to you is what do you believe might be my problem? In my opinion the only other thing I can do is send my ecm somewhere else and have it reprogrammed to make sure thats not the problem.

 

[mattbta]

@Jkpii2000

Is your temp gauge on the dash functioning correctly? Use a scan tool and see what your engine coolant temp sensor is reporting. The default protect mode for a bad ECT is fans on all the time. That's an easy first step.

 

[Jkpii2000]

@Jkpii2000

Is your temp gauge on the dash functioning correctly? Use a scan tool and see what your engine coolant temp sensor is reporting. The default protect mode for a bad ECT is fans on all the time. That's an easy first step.

I will check that thank you but I did replace both sensors about a year ago.

 

[Fless]

Have the fans run all of the time since they were installed and the engine computer was programmed for the fans? Or is this a recent development?

What do you mean by "switched the pins" on the engine computer? Swapping pin locations, or replacing the pins and leaving the wiring on the same pins?

 

[Tonyrodz]

I will check that thank you but I did replace both sensors about a year ago.

I've had sensors be bad right out of the box.

 

[Jkpii2000]

I switched the green and blue wires to the opposite pin locations at the ecm connectors. Yes the fans have always been on from day one.

 

[ScottyBoy]

If you can definitely confirm 100% that the coolant temp sensor is NOT defective, and that the pins are in the proper spots, and the harness is DEFINITELY not damaged (scraped, pinched wires ANYWHERE) then I would start to suspect that your guy didn't program it properly.

 

[ScottyBoy]

And I should have clarified about the harness being damaged. If the vehicle the harness came from was in a collision (even a minor collision) then the wires can become so pinched together that the insulation is compromised and the conductors can be touching. So if one of the trigger wires is damaged and the ground wire is damaged, and the two are touching, then that would cause a constant fan on situation. This is why when I pull harnesses and sell them to people, I thoroughly clean, inspect, and test every wire in the harness, and perform any repairs if needed. Sometimes it may be replacing a few inches of wire, sometimes it's as simple as covering damaged insulation with some marine grade heat shrink tubing ( the kind with glue on the inside of it).
So before calling out your tuner, I'd check the harness and check the coolant temp sensor. A quick and easy way to test the harness would be to unplug both trigger pins from the ECM, and test for ground with a digital multimeter. A test light might pull too much current and not light up if it's a very tiny bit of wire touching. A multimeter will definitely show ANY ground on either of those wire.

 

[Jkpii2000]

And I should have clarified about the harness being damaged. If the vehicle the harness came from was in a collision (even a minor collision) then the wires can become so pinched together that the insulation is compromised and the conductors can be touching. So if one of the trigger wires is damaged and the ground wire is damaged, and the two are touching, then that would cause a constant fan on situation. This is why when I pull harnesses and sell them to people, I thoroughly clean, inspect, and test every wire in the harness, and perform any repairs if needed. Sometimes it may be replacing a few inches of wire, sometimes it's as simple as covering damaged insulation with some marine grade heat shrink tubing ( the kind with glue on the inside of it).
So before calling out your tuner, I'd check the harness and check the coolant temp sensor. A quick and easy way to test the harness would be to unplug both trigger pins from the ECM, and test for ground with a digital multimeter. A test light might pull too much current and not light up if it's a very tiny bit of wire touching. A multimeter will definitely show ANY ground on either of those wire.

I will test the harness and temp sensor soon. The doner Tahoe was in very good shape but doesn’t mean it was previously in an accident. I will have to find my notes (they are packed somewhere since I just moved) and check which trigger pins go to which color ecm connector and pin location. I believe it’s pins 42 and 38 but can’t remember which color ecm connector and wire to pin location. Do you remember off hand what trigger wire to what number pin and pin location to color connector? Thank you for all of the info. I appreciate it!

 

[Dantheman-2003]

All: Can’t remember if I already provided an update, but my E-fan install was successful. Pulled my OEM harness out of my 05 Yukon and installed it in my 03 Tahoe. Thanks to all the support here on the thread. Scotty is the E-fan man! I’ve been up and running for several months, tuned, re-geared and running strong with E-fan setup.

Thanks to all.
Dan