Laptop fan wont work when I screw in heatsink

Hey guys! Haven't been here in a while. Now I'm on the other side of the people who are usually helping out

I'm having a problem with my Dell Studio XPS 1340 Laptop. The display cable was going bad so I went ahead and replaced it. When I had everything put back together the fan was making some noise. I had gotten a cable slightly off from where it should have been and it was hitting the fan. So instead of taking a whole bunch of things apart I decided to take out the fan and readjust the cable. To do this I had to take the heatsink off and I cleaned up the old thermal paste and replaced with AS5. Now when I screw down the heatsink the fan won't turn on! If I leave screw number 3 of the heatsink loose then the fan stays on but the laptop quickly shuts down to prevent overheating.

Now I have tried pushing down on the heatsink and the fan still turns off. Im thinking then there is a short that the heatsink is making and not the screw. I've put electrical tape on the heatsink mount (on the back side of the motherboard) and I've put electical tape where the heatsink screws in. Still nothing.

Any help or thoughts would be appreciated

 

No, that would be number 1. If you look in the second picture the screw numbers are there but they are upside down. From what I can tell there appears to be no pressure on the fan connector but I can put tape on it to rule out any shorting.

 

There is a lot of thermal paste there.Have you tried using less to displace the heat through the copper?

 

seen this before.first make sure the heatsink is seated firmly.go so far as to turn it back and forth a little while applying pressure on it.then tighten the screws in a crisscross fashion a little at a time untill they are tight.not too tight either.a little screwing around (pun intended) and you should have it.

 

I will check the tightness although it was pretty tight. As for the too much thermal paste I took these pictures after taking off cleaning and reseating the heatsink many times. This was probably my 6-7th application of thermal paste and I got a little sloppy. Even with perfect amounts of paste it was doing the same thing.

 

Most have temp sensors with a limit to shut down if reached,this may have been altered some way.

 

That is still WAY too much thermal paste (the pinkish blob) and actually will cause inefficient heat transfer. Also, what is pushing up against the paste where you can see it pushed in? Paste can be electrically conductive. The amount of paste there can keep the heatsink from going as low as it's supposed to go, especially in laptops, and when you put the case back together this can cause undue pressure to be applied if the heatsink now contacts the case because it sits a little higher. This could also cause a circuit with any flaw at all to crack just enough to separate when the pressure is applied.
Just some thoughts, I've seen some weird things happen because of bad thermal paste jobs in the past.

 

Hey buddy

It's bloody massive, it almost looks like a blob of bubble gum lol!
I've seen hundreds of factory paste jobs, even this solid type used on some, but I've never seen one with such a large block of it so that's why I had to ask. I'm not as familiar with laptops as I am with tower PC's so it could be more common than I know.

It's strange that a single screw would cause this so initially I thought of a short as well but then when he said it's only when tightened down, that makes me think of pressure somehow and with the fan connector being right beside the heatsink (going over it actually), the coincidence is curious

Later ddp!
Dave.

 

Any update from the OP ? Like i said it took me by surprise the amount of thermal compound used that's why i had mentioned it.As you said when you applied the fan screws you leave one screw (3rd) loose so i think you might have pushed the over-used thermal compound onto the mobo causing a short like mentioned by ChappyTTV.You may have to get the whole mobo out of the casing and look for scorching,blown capacitors/components.Or because the fan did not work properly on the gpu you may have fried the chip beyond repair.

 

That's not thermal paste... it's a thermal pad lol. Like I said I doubt it's a thermal paste issue because I put on the correct amount before but I'll take the motherboard out and clean it down with 99% alcohol to remove any residues. I've been really busy so I haven't had a chance to work on it.

I will update you guys on what happens! Either way there wasn't enough thermal compound to push it over to the motherboard. Some overlap from the die but not enough to get to the mobo.

Either way I will try all suggestions and report back. Thanks for all the advice!

 

Tried again lot less TP same result. Everything is screwed down tight. I tried spraying down the motherboard with MAF sensor cleaner (electrical cleaner for car MAF sensors, it's supposed to leave no residue)

Tried putting electrical tape over the capacitors on the GPU and the fan works with the heatsink tight but it shuts down like its overheating within 20 seconds of booting into windows. However the heatsink is tight and fan is working so Idk why it would be overheating.

 

Tried that but BIOS doesn't show temp. I can get into speedfan before it shuts down and it shows temps in the 40s-50s. I'm considering software problem. Gonna try a linux live CD now.

 

i still stand by my first post. uninstall the fan from the heatsink,redo the paste on the heatsink, then loosly install the fan on the heatsink.start your machine and then in a crisscross fashion tighten the screws.i had the same problem with my computer.after tightening the screws the fan wouldnt even turn.it takes a little messing around but im sure this is your problem.

 

I wanted to update this thread as questions without resolutions annoy me.

Guys I tried everything and nothing was working. Trust me I'm not really a newbie to computers either but I couldn't figure it out. So I just spliced the fan wires to a USB cable, drilled a hole in the bottom cover for the wire and hooked it up to my USB port. Laptop works great now although a little loud haha. We have it set up as a desktop and it's working now at least.

 

Those laptop fan header connectors don't take kindly to pulling from the cables. The cables themselves are usually just a few strands of copper, so even slightly bending might break them, especially if they've been in a dry environment. I have myself once broken off a cable from the header connector (fan-side) and the PWM wouldn't work because the wire was loose. The plastic is also very flexible on the connectors, so you can easily fit the cable upside down. Sometimes the cable can fit in either way and you have to figure out which way it's supposed to go in.

All laptop fans, ODDs and HDDs use 5V as their maximum operating voltage, so using the USB (5V) as a power supply to the fan makes it spin at 100%, so of course it's going to be loud. In one laptop I soldered long cables from the HDD power connector to the fan to make it spin at 100% because the laptop (acer) was letting the CPU hit tjmax before boosting up the RPMs on the fan.

You could maybe use a potentiometer on the fan to adjust the speed manually if you want.

 

Instead of drilling and all that nonsense you could have taken a pin to the fan connector and removed the blue wire. The blue wire controls pwm so it would make your fan run at 100% (just like it does now). You could also probably get another fan to restore the the computer to it's factory state.

With certain gaming computers I mod and refurbish I like to put a switch on the pwm wire so you can boost your fans with a flick of a switch. I did this mod exclusively for Asus G50-51 owners on a couple different forums.

This is a picture of an Asus G51vx after I got the idea to put a switch on the pwm wire.



This is how I ran my wires and mounted the switch. The switch was shaved down a bit so it could fit in the hole.


Finished product


Hope this gives you an idea of what can be done to battle your fan/cooling issues.