[SOLVED] How to replace the CPU fan on an old Dell PC ?

[Minaz]

I have an old Dell Inspiron 5680 Desktop PCwith an i7-8700 CPU that on every boot the BIOS does a hardware check and throws out a CPU fan failure message.

I've read that CPU fans come in various sizes and that in the past Dell also used proprietary fan connections.

I bought this desktop a few years ago for cheap and used on Ebay, so its not like this was a big financial investment, however, I have been using it a fair bit and put quite a lot of time (not so much money) into it, so I'd like to keep it running if possible.

The priority for me would be a simple and easy fix as opposed to anything that would require a lot of messing around (rewiring anything would be beyond what I am comfortable doing for example), but also preferably a cheaper fix since this is not an expensive computer to begin with.

Is there a part that I can just order from somewhere still in operation that I can simply swap out and replace the old fan, or if not, at least with an adapter etc? How would I know which fan would work? I understand that the number of pins, pin layout, and communication with the Dell bios have been noted on the Internet as potential problems and hope to avoid these.

Thanks!

 

[CountMike]

I've read that CPU fans come in various sizes and that in the past Dell also used proprietary fan connections.

I have an older Dell dekstop (Dell Inspiron 5680, with an i7-8700 CPU) that on boot, the BIOS does a hardware check and throws out a CPU fan failure message.

I bought this desktop a few years ago for cheap and used on Ebay, so its not like this was a big financial investment, however, I have been using it a fair bit and put quite a lot of time (not so much money) into it, so I'd like to keep it running if possible.

The priority for me would be a simple and easy fix as opposed to anything that would require a lot of messing around (rewiring anything would be beyond what I am comfortable doing for example), but also preferably a cheaper fix since this is not an expensive computer to begin with.

Is there a part that I can just order from somewhere still in operation that I can simply swap out and replace the old fan, or if not, at least with and adapter etc? How would I know which fan would work? I understand that the number of pins, pin layout, and communication with the Dell bios have been noted on the Internet as potential problems and hope to avoid these.

Thanks!

Measure fan's diameter and number of wires, seek one like that.
A picture of related parts would be good to have.

 

[Lutfij]

You can drop in pretty much any aftermarket cooler onto the socket as the motherboard's CPU mounting holes are for LGA1151 meaning any cooler that supports the LGA115x support will work. Might want to read through this thread;
https://www.dell.com/community/en/c...on-for-inspiron-5680/647fa1a1f4ccf8a8de6e8b90
and using the Vetroo V5's height, you should be good with a sub-155mm tall cooler. The Vetroo V5 is 148mm tall...and so is this;
https://pcpartpicker.com/product/8wZXsY/thermalright-assassin-x-se-3277-cfm-cpu-cooler-ax90se-v2

^ All of those suggestions are based of the assumption that you're located in the USA. If you're not located in the USA, please pass on your location, your budget and your preferred site for purchase.

 

[Misgar]

I have an old Dell Inspiron 5680 Desktop PCwith an i7-8700 CPU

If your heatsink fan looks like this, there's a vague possibility you might be able to change the fan on iots own, without removing the Aluminium heatsink.
https://www.pcmag.com/reviews/dell-inspiron-gaming-desktop-5680#

The CPU fan in this photo looks as if it might be a standard 80mm x 80mm computer fan. What I can't make out from the photo is how the fan is secured to the metal heatsink. It might be spring loaded clips or it might be four screws.

The reason I offer this suggestion is that if you've never removed or fitted an LGA1151 heatink in your life, you may get confused with the necessary steps.

The old heatsink might be screwed down to the motherboard, or special expandable clips might be pushed through holes in the motherboard, at the four corners of the CPU socket. Unscrewing a heatsink is easy if that's how it's mounted.

If you need to unclip the entire heatsink from the motherboard it's less obvious. There's a special technique which involves rotating four plastic clips through 90 degrees to release the heatsink, followed by a second operation to plug in and secure the new heatsink. Get it wrong and the new heatsink makes poor contact with the CPU and the chip overheats.

View: https://www.youtube.com/watch?v=3xPrd6FBTS0


The problem arises if you're unsure whether or not the four clips on a new heatsink are locked firmly into place, or merely pushed through the motherboard holes and in danger of falling off.

There's also the need to clean off all the old thermal paste (usually grey) from the CPU, before fitting the new heatsink. Some heatsinks come with thermal paste pre-applied, others assume you'll use your own paste, or the paste they supply in a tube with the new heatsink.

If you need to apply paste yourself, the amount is important. No paste is bad. Too much paste is also bad. It can squeeze out around the edges of the CPU and contaminate the edges of the socket and the motherboard. Paste inside the socket is bad news.

The correct amount of paste is usually described as a small pea-shaped blob, about 4mm diameter, placed on top of the CPU in the middle. The blob spreads out when the heatsink is tightened down.

If all this sounds like a pain to the uninitiated, it's because it is. Once you've done it several times it becomes easier, although it's still possible to make mistakes if you can't remember which way to rotate the stupid clips.

That's why I suggested removing the fan only if that's feasible. It saves removing the heatsink, cleaning off the old thermal paste, applying new paste (if none is pre-applied) and attaching the heatsink. It's all a bit of a faff.

If you do change the fan on its own, you'll probably need a Pulse Width Modulation (PWM) fan, which allows the motherboard to vary the fan speed depending on how hot the CPU gets.

https://www.amazon.com/80x25mm-Computer-Case-Fan-PWM/dp/B0067D7IMM

A PWM fan has 4 wires. Check your existing fan. It probably has 4 wires. PWM sends a control signal (square wave) to a circuit board in the fan, which changes the fan speed, depending on the CPU temperature.

A cheaper (incompatible) fan has 3 wires (no PWM). They're OK for very basic case cooling, but it's more difficult to vary the speed of a 3-wire fan, unless you have some form of voltage control.

Good luck, whatever you decide to do.

 

[Paperdoc]

OK, a few more details.

VERY FIRST STEP: check your fan's connections. This is ALL triggered by an on-screen alarm about failure of the CPU cooler fan. That is caused by NO fan speed signal reaching the CPU_FAN header. That, in turn, may be because that fan really HAS failed and is not turning, or is turning too slow. OR it could be simply that the signal wire for it is loose or has a dirty contact. So do these tests FIRST.
1. Open the case and watch that fan closely when you first start up from a COLD system. The NORMAL situation is that when you push the power button the fan will start up immediately at full speed. After a few (5 to 10) seconds the fan will slow down to the low speed required for cooling of a cold system, but it WILL keep running. If that happens you know that fan has NOT failed and the warning message is incorrect. However, if the fan does not start, or stops after starting, then the fan really is faulty and needs replacement.
2. If that test says the fan is OK, shut down and try this. Carefully unplug that fan from its CPU_FAN mobo header. Now re-connect. Repeat several times, ending with it re-connected. Start up and see whether that warning message is still there even though the fan is working. This action MAY "scrub" dirt and oxidation from the fan connection pins and fix a bad connection so the speed signal can get through.
3. If this has NOT solved the problem then you may need to replace the fan.

What you need is a standard 80mm size 4-pin fan, aka PWM fan. (The SIZE number of a fan is the length on one side of the square frame. MEASURE your old fan frame to verify that size.) In searching for that look for a fan called a Pressure Fan, and not an Airflow fan. A "Pressure fan" is designed to blow air thought some airflow resistance such as the finned heatsink. Among those, look at the Airflow max rating in CFM - more is better. Its max Pressure rating should be over 1.0 mm of water, maybe over 1.5 mm.

It is MUCH better to change ONLY the FAN. Most instructions concentrate on replacing the entire heatsink and fan assembly. But that REQUIRES that you get exactly the right part AND that you remove the old one (can be hard to do because the thermal paste may be hardened), clean off all old thermal paste, and use new paste as you install the new one. HOWEVER, if you look closely at what you have you can see that there are four screws to fasten the whole unit on top of the CPU. BUT there are four DIFFERENT screws that merely fasten the fan to the underlying heatsink. That fan is a standard 80mm fan so you do NOT need exactly a Dell part. PLUS if you replace the fan only you do NOT need to worry about all that thermal paste trouble.

There MAY be a small problem with fan electrical connections. Dell says this fan uses a "standard 4-pin fan". But in SOME cases Dell used this with wires in its connector in different positions from real "standard". In most cases this means only the Speed signal (Yellow wire normally on Pin 3) and PWM signal (blue wire normally on PIn 4) are reversed. In other cases Dell really did use exactly standard wiring. How to tell? Assuming you don't have access to fancy tech tools, the simple way when you get the new fan is BEFORE installing it you do this test. With the system shut down, disconnect the actual CPU cooler fan from the CPU_FAN header and plug in there the new fan. For a short time turn on your system and watch for that Fan Failed warning. You can run this way for a short time with NO actual CPU cooling, but not long so turn off soon. IF the new fan DOES start up, slow down and keep running AND the warning message does NOT appear with the new fan connected, then that new one IS wired just right and you will have NO problems once it is installed. If the message is still there or if the new fan does NOT start, then the wiring of the new fan is not Dell's way and some work is rquired to change that. If that happens, post back here and we can advise.

By this point hopefully IF you need to replace the fan and it IS wired correctly, the following should help. One video I found here

View: https://www.youtube.com/watch?v=d5LiHidW_18&t=195s


shows a system with duct or shroud fastened over the CPU cooler that needs to be removed to reach the actual cooler. If you have that, do that step. Then do NOT follow thre rest! The rest of that video follows the Dell procedure to remove the entire heatsink and fan assembly and replace it all.

Instead, disconnect the fan from the CPU_FAN header. Find the four screws that fasten the fan to the heastink and remove them. Look closely at the frame of the new fan. Normally it will have two arrows on it. One points around the frame to show the direction of fan rotation. The other poinrts through the frame to show air flow direction. Place the new fan on top of the heatsink with air flow towards that heatsink, and align the four corner screw holes with the matching holes in the heatsink, then install its four screws. Plug the fan cable into the mobo CPU_FAN header. If you have it, re-install the shroud per that video. Before closing up, turn on your system, observe the fan action to be sure it's working, and check whether the warning message is gone. Close up and relax.

 

[Minaz]

OK, a few more details.

VERY FIRST STEP: check your fan's connections. This is ALL triggered by an on-screen alarm about failure of the CPU cooler fan. That is caused by NO fan speed signal reaching the CPU_FAN header. That, in turn, may be because that fan really HAS failed and is not turning, or is turning too slow. OR it could be simply that the signal wire for it is loose or has a dirty contact. So do these tests FIRST.
1. Open the case and watch that fan closely when you first start up from a COLD system. The NORMAL situation is that when you push the power button the fan will start up immediately at full speed. After a few (5 to 10) seconds the fan will slow down to the low speed required for cooling of a cold system, but it WILL keep running. If that happens you know that fan has NOT failed and the warning message is incorrect. However, if the fan does not start, or stops after starting, then the fan really is faulty and needs replacement.
2. If that test says the fan is OK, shut down and try this. Carefully unplug that fan from its CPU_FAN mobo header. Now re-connect. Repeat several times, ending with it re-connected. Start up and see whether that warning message is still there even though the fan is working. This action MAY "scrub" dirt and oxidation from the fan connection pins and fix a bad connection so the speed signal can get through.
3. If this has NOT solved the problem then you may need to replace the fan.

What you need is a standard 80mm size 4-pin fan, aka PWM fan. (The SIZE number of a fan is the length on one side of the square frame. MEASURE your old fan frame to verify that size.) In searching for that look for a fan called a Pressure Fan, and not an Airflow fan. A "Pressure fan" is designed to blow air thought some airflow resistance such as the finned heatsink. Among those, look at the Airflow max rating in CFM - more is better. Its max Pressure rating should be over 1.0 mm of water, maybe over 1.5 mm.

It is MUCH better to change ONLY the FAN. Most instructions concentrate on replacing the entire heatsink and fan assembly. But that REQUIRES that you get exactly the right part AND that you remove the old one (can be hard to do because the thermal paste may be hardened), clean off all old thermal paste, and use new paste as you install the new one. HOWEVER, if you look closely at what you have you can see that there are four screws to fasten the whole unit on top of the CPU. BUT there are four DIFFERENT screws that merely fasten the fan to the underlying heatsink. That fan is a standard 80mm fan so you do NOT need exactly a Dell part. PLUS if you replace the fan only you do NOT need to worry about all that thermal paste trouble.

There MAY be a small problem with fan electrical connections. Dell says this fan uses a "standard 4-pin fan". But in SOME cases Dell used this with wires in its connector in different positions from real "standard". In most cases this means only the Speed signal (Yellow wire normally on Pin 3) and PWM signal (blue wire normally on PIn 4) are reversed. In other cases Dell really did use exactly standard wiring. How to tell? Assuming you don't have access to fancy tech tools, the simple way when you get the new fan is BEFORE installing it you do this test. With the system shut down, disconnect the actual CPU cooler fan from the CPU_FAN header and plug in there the new fan. For a short time turn on your system and watch for that Fan Failed warning. You can run this way for a short time with NO actual CPU cooling, but not long so turn off soon. IF the new fan DOES start up, slow down and keep running AND the warning message does NOT appear with the new fan connected, then that new one IS wired just right and you will have NO problems once it is installed. If the message is still there or if the new fan does NOT start, then the wiring of the new fan is not Dell's way and some work is rquired to change that. If that happens, post back here and we can advise.

By this point hopefully IF you need to replace the fan and it IS wired correctly, the following should help. One video I found here

View: https://www.youtube.com/watch?v=d5LiHidW_18&t=195s


shows a system with duct or shroud fastened over the CPU cooler that needs to be removed to reach the actual cooler. If you have that, do that step. Then do NOT follow thre rest! The rest of that video follows the Dell procedure to remove the entire heatsink and fan assembly and replace it all.

Instead, disconnect the fan from the CPU_FAN header. Find the four screws that fasten the fan to the heastink and remove them. Look closely at the frame of the new fan. Normally it will have two arrows on it. One points around the frame to show the direction of fan rotation. The other poinrts through the frame to show air flow direction. Place the new fan on top of the heatsink with air flow towards that heatsink, and align the four corner screw holes with the matching holes in the heatsink, then install its four screws. Plug the fan cable into the mobo CPU_FAN header. If you have it, re-install the shroud per that video. Before closing up, turn on your system, observe the fan action to be sure it's working, and check whether the warning message is gone. Close up and relax.

So it turns out that the CPU fan was spinning. It looked like it was spinning quite fast, but how fast? I didn't know, no way to measure. However, I did the trick about reconnecting the fan wire and indeed it solved the problem. The bios no longer complained about the fan either. The odd thing is that after all this, the fan is now making a slight rickety hum where there wasn't one before. But its not very noticeable.
The hardest part was simply opening up the case. Engineers do engineer things, and boy is it ever a hairy moment when you try to open a case were there are clips and guides and screws all in one. Took me forever and I thought I wasn't going to make it. And this was supposed to be an easy open case too (at least according to the description). Thanks for the solve!