How to: Replacing Cooling Fans and Thermal Compound on a Video Card

Reassembly

Now that everything is cleaned up and ready to be put back together, we can turn our attention back to the fans. I got my first replacement fans from eBay in about 3 days, so I had a bit of time to work on the guide in between ordering them and actually receiving them int he mail. But I now have them in-hand and I am ready to continue. As mentioned earlier, these “close enough” replacement fans came with 4 wires, so a bit of modification is needed. Since this particular fan set came with 2 fans already connected, for a dual fan setup, I can simply make one splice to connect it to my harness.

HD7970 Fan Repair 009This will work out nicely, as the Gigabyte fan layout was such that the first fan was actually a 3 pin variation that could sense the fans RPM to send back to the controller. So this fan would act as the “guide” for the other two, which act in a more passive role and with only 2 wires simply speed up or down depending on whatever voltage they are given.

To make splicing the new harnesses together easier, I cut off the connector end of the wire from one of the old fans (shown to the left) and will make the splice a few inches down from where the new connector is on the new harness. This should help keep everything neat and tight so as to fit back in the shroud without any problems. Referring to the table back on page 2, I can see that the black (ground) and yellow (hot) wires will be what I need to use.

HD7970 Fan Repair 012A quick and easy way to test this theory is to use a 9 volt battery. While the fans are rated at 12 volts, 9 V is plenty to test if the wiring is correct and the blades spin in the right direction. Placing the yellow wire on the positive battery terminal and the black on the negative confirms this is all correct as the fans begin to spin. Do note that the PWM fan spec calls for a rotational lock of the the fan for wrong polarity, so they will only spin in one direction with the positive terminal on yellow, reversing the wires will cause the fan to not spin ensuring proper rotation.

With the testing out of the way, now I need to splice the harnesses together. I strip back some of the insulation on the yellow and black wires on the new harness, and fold the remaining two wires back out of the way. I twist the wires together with the ones from the original fan connector (red to yellow, black to black) and put a dab of solder on each connection to make sure everything will stay together. Once the solder has cooled, I tape everything up nice and tight using electrical tape, making sure to provide plenty of insulation between any exposed wires.

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Now it might not be the prettiest looking thing out there, but it should do the job nicely and will be hidden away behind the fan shroud, so it just needs to be functional, not attractive. Tucking all this extra wire and taped splices back into the small channel provided on the shroud proved to be an exercise in patience, but after about an hour of fiddling around I managed to get it tucked in there pretty well. The main thing you need to watch out for is that you do not want any wires to come loose where they could interfere with the fan rotation.

Below you can see the completed product and also notice the original “head” fan on the right with the extra yellow sensing wire.

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So the fans are in and harnessed up we are ready to assemble everything back together. Locate all the parts, screws, and tools and lets get to it

HD7970 Fan Repair 015First we need to attach the fan shroud to the heat-sink assembly. Set both pieces down on a flat work surface and making sure they are aligned such that when you flip the fan shroud over onto the heat-sink it will be in its final position correctly. In this orientation you should be able to easily reconnect the fan harness to its matching connector on the PCB.

Now flip the shroud over to cover the heat-sink. You will need to carefully guide the four mounting tabs between the outer row of heat-sink fins on either side to align with the mounting holes. Simply screw this back together (may take a bit of wiggling until you get the holes and screw aligned) and you are finished with this half. Note, if you had to loosen the end bracket, also be sure to return those fasteners to their proper positions on the PCB and tighten them up as well.

You may need to give a final quick blast of canned air over the heat-sink and GPU mating surfaces to blow off any accumulated dust. If you just finished cleaning you should be good to go, as my parts were idled for about 3 days.

Place a small dab (about the size of a cooked grain of rice) of thermal compound on the center of the GPU core. Arctic Silver recommends not spreading it out as it will self spread over time as the card is thermal cycled (tuned on and off a few time). Being old-fashioned, I compromised and spread it out about half of what I really wanted to, which would have been over the entire surface. I also put small dabs on the surrounding aluminum block, as when I took it apart it originally looked like some had been applied here as well.

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With the thermal compound in place it is time to reassemble the two halves. I found it easiest to have the heat-sink portion laying face up on a work surface and slowly lowered the PCB into place. You can carefully lower it and by peeking through the 4 mounting holes, line it up as it gets nearer the screw pegs. You want to try and not move it around too much as they two halves join together so as to not dislodge the thermal compound in areas where your do not want it to go.

Once it is in place, the matching screw pegs should be clearly visible and centered into each of there respective holes (shown below right). A firm bit of downward pressure to push it together and make sure everything is properly seated is recommend before inserting the screws.

HD7970 Fan Repair 018The screws should all be started just enough that they do not come loose, but do not tighten any of them just yet. Make sure all 4 screws are in place and have just started to thread and then follow a crisscross pattern as shown to the right. Begin by snugging each one up just until the first bit of resistance is felt and then move on the the next.

Once they are all snug, follow the same pattern, again giving each one a final twist to tighten them all down. This method helps to seat the plate properly and helps avoid a situation where the mating surfaces are uneven.

 

 

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With everything back together and tightened up we are just about ready to put it to the test. I usually spin the fans by hand a bit to make sure there is no resistance due to errant wire or binding, you can also give a quick puff of air to each one from your mouth and they should spin freely. Give everything a once over to make sure there are no loose parts, connectors, or missing fasteners and we can re-insert the car into service.

I normally have a dedicated system setup where I not only can run tests on single cards, but also return cards such as the one we just worked on back into service. I do this, as it has never happen, but just in case something catastrophic happens, such as the card shorting out and taking the system with it, I don’t destroy a production rig in the process. In any event, it is a good idea to be ready with the power switch in any case.

GPUz_Fan_RepairInserting the card into my test system,  and making sure everything is properly wired,  I power it up and enter into BIOS at first. I simply let everything run this way for about a minute so I can concentrate on looking out for anything unusual. I check the GPU fans are running and no unusual sounds, or smells are emanating from anywhere. Once I am confident the initial power-on is good, I let the system boot normally.

Once into the OS, usually Windows for me, I will quickly fire up a monitoring program that can display the GPU temperatures. This could be the built in Radeon Settings software from AMD, GPUz, MSI Afterburner, or any program that you can monitor real-time GPU temperatures with. In this case I am using GPUz, as I like the ability to set the GPUz window title to display the GPU temperature, so I can easily keep an eye on things.  The idea here is to make sure the GPU core temperature doesn’t suddenly spike up out of control and damage your video card.

As with the initial boot, I simply let the system idle for awhile with only the OS and GPUz running. The temperatures at idle should be in the 40° C range, but anything under 50° C should be ok. The image to the left was taken after I had been mining for about 10 minutes, so the temperature is around 64° C under load.

Letting the system idle for five minutes or so, as long as I do not notice any temperature spikes, or again strange noises, smells, etc. that would indicate trouble, I am fairly confident all is well and we can begin more stressful testing. At this point, I will fire up the mining program to put the GPU under load and let it mine for about 10-15 minutes, keeping an eye on everything, especially the temperatures. In this case it rose to and evened out around 64° C as shown to the right, which is pretty acceptable.

I will normally shutdown the PC at this point for about 30 minutes or so, in order for to cool completely and to get one thermal cycle out of the way for the freshly applied thermal compound. Since once back into production the GPU won’t get many of these cycles, it doesn’t hurt to perform a few up front.

After having a chance to cool off, I will again boot the system, run GPUz and the mining program, this time letting it run for an hour or two to make sure it is stable over the longer term. You do not have to be as vigilant at this point, but it does not hurt to check in on the temperature every once in awhile. After a good workout while mining for at least an hour, two maybe better, I will again power down the rig and let everything cool completely, this time leaving it off a good hour or until everything feel room temperature to the touch to ensure a proper thermal cycle has completed.

After this second cycle, I will usually either put the card back into a production rig or continue more strenuous testing for other reasons, but by this point I am confident the card is back to normal and the maintenance has been successful. Depending on how particular you are, you may want to have a few more cooling cycles for your freshly repaired card to properly set the compound, but I have done it both ways and never had any issue once the initial few times have been completed.

So that concludes this article and we covered a lot of information that I hope you find useful. As usual please feel free to leave any comments or questions below.

 

2 Comments

  1. Nice article! I had to mod the frame on a pair of 92mm fans with pwm to fit my card and found your article looking for the pinout of pwm fans. You make no mention about the thermal pads needed for the ram chips, i found they seem to be recommended to keep mem temp on check.

    • Thanks for the comment.

      Yes, the thermal pads are indeed important and for the most part I just clean them off with a quick wipe of a alcohol moistened cloth and leave them be.

      While there are after-market replacement pads available, in most cases the originals will continue to work just fine assuming they are not damaged in any way and continue to make contact with the heatsink once it is reattached.

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