How to fix System Fan (90B) error on a HP Compaq Presario Laptop

This article explains how to resolve a System Fan (90B) error from appearing when you start up your HP Compaq Presario Laptop. The laptop featured in this article is a CQ56. The full error reads:

The system detected that a cooling fan is not operating correctly

And looks like this:

HP Compaq CQ56 showing system fan error

The error is caused by the system cooling fan not spinning. Notice I said “Not spinning”. The most likely cause is that the fan is stuck or has fell off its spindle. Rarely are any new parts required for this fix but you will need thermal compound paste if you have to remove the heat sink from the processor (very likely).

In this example I have used a HP Compaq Presario CQ56 but this article is also applicable to many other laptop models as well as the CQ series from HP Compaq.

If you are very lucky you could poke a straightened paper clip through the holes for the fan and try and get the fan to start spinning. You do risk damaging the fan but it may be all that is required. More likely you are going to have to take the laptop apart which is described as follows:

HP Compaq removing covers

Remove the battery and the screws holding the hard drive and memory compartment panels in place and then remove the panels.

Once the panels are removed the laptop should looks something like this:

HP Compaq removing hard drive and wifi card

Pull the tab pointed to at the lower right of the picture above, this disconnects the hard drive from the motherboard. Then undo the three screws holding the hard drive in place. The hard drive will then lift out.

Also unclip the black and white wire from the wifi card pointed to by the two arrows on towards the middle of the photo, the undo the screw holding the wifi card in place. The wifi card should spring up allowing you to remove it from motherboard.

Note: You could remove the memory modules at this point if you want to. However, I leave them in so that I can test the basic functionality of the laptop before putting the whole thing back together once I think the fan is fixed.

Your laptop should now look like this:

HP Compaq with hard drive and wifi card removed


Next remove all the screws holding the base to the top including the screws that hold the keyboard in. The screws are all circled in the photo below. Make a note of where the shorter screws come from. Also pull the DVD/CD Drive out from the left of the laptop.

HP Compaq screws to remove to open it up

Make sure you get all 7 screws from within the battery compartment

Make sure you get all 7 screws from within the battery compartment

Next the keyboard needs removing. Using a sharp knife lift the keyboard starting at either of the points pointed to by the arrows and work to the other end.

HP Compaq keyboard removalBe careful as there is a ribbon connecting the keyboard to the motherboard. To release the ribbon carefully lift the brown part of the connection and gently pull the ribbon out.

You should now have a laptop that looks like this:

HP Compaq releasing top coverYou need to undo the screw circled. Undo and remove the 3 ribbons and pull the speaker cable out of the motherboard (top right).

Now put the laptop onto its side so that the DVD/CD drive is easily accessible. Carefully separate the top of the base from the bottom as shown below:

HP Compaq opening the laptop

Carefully work your way around the laptop so that it is open all the way round. The two parts should separate completely showing the motherboard.

Next you need to remove the wires connected to the motherboard and undo the screws holding the motherboard to the base.

HP Compaq removing motherboard

Undo the two screws circled. Then remove the ribbons by un-clipping the brown clips pointed to by the red arrow. Pull the tabs on the connectors pointed to by the orange arrows and gently pull the cables out of the sockets pointed to by the purple arrows. The motherboard is now ready to remove though the power connector pointed to by the green arrow is still connected.

Lift the motherboard from the right hand side slightly so that you can disconnect the power connector. Once removed the motherboard should lift out. Ne careful as there is a metal clip at the top left holding the motherboard in, you need to slide the motherboard down a little before completely lifting it out.

HP Compaq Presario CQ58 motherboard top


Turn the motherboard over to see the fan

HP Compaq Presario CQ58 motherboard underneath


At this point you may see that the fan is full of dust, has something stuck in it (in my case there was a screw loose in the fan). Try and move the fan, does it spin freely? If not try squeezing the top and the bottom of the fan housing, does the fan click into place? If it does then the fan had fell of its spindle. Clean the fan with a vacuum cleaner and a paint brush to remove dust.

If you need to investigate further then undo the three screws securing the heat sink to the processor.

HP Compaq Presario CQ58 removing the heat sink from the motherboard

Note that if you do this then you are going to have to clean the processor and heat sink of thermal paste and then reapply thermal compound paste to the processor.

HP Compaq Presario CQ56 Heat sink and fan - top

HP Compaq Presario CQ56 Heat sink and fan – top

HP Compaq Presario CQ56 Heat sink and fan - bottom

HP Compaq Presario CQ56 Heat sink and fan – bottom

If you want to test the fan then you need to apply a maximum of 5 volts to the red wire and use the black wire as neutral.

Providing the fan spins then reassemble in reverse.

Original pictures here -> HP Compaq Presario CQ56 photos



How to fix System Fan (90B) error on a HP Compaq Presario Laptop — 44 Comments

  1. Absolutely spot on. Large ball of fluff stopping the fan from turning. Stripped it as above and removed it and all was well again. Many thanks

  2. Thanks a lot I took it apart and vaccume all lent from fan and air blewwdust from laptop inside I reconnect and it is working!!!

  3. Thank you worked great! My fan was still turning but would overheat in minutes, found a little dust build up blocking the exit find for the fan! Thank you so much for the awesome tear down instructions.

  4. Thank you so much for posting this instructional. I was able to identify a clogged fan using your informational/screenshots.

  5. Another satisfied customer! Thank you very much for taking the trouble to publish this useful guide.

    Another Presario CQ56 returned to service.


  6. Great info! I had this same problem, followed your directions exactly and it worked! I ended up getting the thermal paste from radio shack and cleaning the old stuff off and replacing it. My fan was clogged with dust. I blew it all out with compressed air.

    Now my laptop is quiet, cool, and working great!

  7. i had a big problem i tryed to use my vacuum cleaner on the fan thing and when i start up it makes a loose vibrating noise like the fan fell off what do i need to dooo

  8. hello, i have a compaq cq58 laptop and my cooling fan is not working properly.. Now my question is, can you please do a video on it on how to fix this problem? Thanks

  9. Wow that was odd. I just wrote an extremely long comment but after
    I clicked submit my comment didn’t appear.
    Grrrr… well I’m not writing all that over again. Regardless,
    just wanted to say great blog!

  10. I just wanted to thank you for posting this. Since I read from the beginning of your instructions; I of course tried the easiest thing first-to stick something small in and get the fan spinning…and it worked! 🙂 I don’t have any paperclips laying around, so I grabbed one of those hand held flossers, and a safety pin as a back up. The flosser did the job. I just slowly and carefully turned it a little at a time( with my computer shut of, of course), and then it moved easily, as if something had been freed from it’s path. So helpful! Thanks again. 🙂

  11. Your article is very informative, i have had my laptop apart due to to overheating, and have cleaned the cooler fan and heat sink, it is still apart a the moment awaiting my pay day so i can get some thermal paste. I have noticed that on the GPU heat sink, there is a thin pad of something that has the appearance of soft Blu-tac, on mine i have removed this but in your article you have made no mention of it, was i right to remove this? If i was wrong, where can i get another one? Many thanks.

    • that is thermal paste and you should replace it before using the laptop as this will lead to overheating of the GPU. I recommend using Arctic Silver thermal paste

  12. hi,i have a big problem my hp cq42 laptop cooling fan auto on when i connect the battery or charger and have not power my laptop.and i don”t on it.

  13. Hey thanks for posing this! I didnt even need it in the end… I saw you said you could spin the fan through the vents carefully. So I blew through it to get some dust out. It did, but went in my mouth (sad face) and then I sat my laptop while I played some GTA and it suddenly tried getting the fan to kick in and a huge puff of dust came out #scary. Made a funny noise for a sec and now sounds like it is working ace. I don’t recommend blowing into the vent, you will probably just blow the dust on other compartment or in your mouth, might be dangerous as well. Anyway thanks!

  14. Thanks heaps for posting this, by following the instructions with illustrations I was able to get rid of the error on my laptop. My only tip is that it helps to have separate containers to put the screws in as there a few different sizes that go specific places. Thanks again!

  15. Thanks for the strip down information it worked a treat for me with the easy to follow instructions thank you

  16. Wonderful detailed and well illustrated article. I have a strange situation as I get the error message but the fan is running noisily and appears at the right speed. I will change the fan but I guess it could be a false warning coming from the BIOS

  17. Bravo… it works… i used the simplest illustration by rolling d fan wt tiny object… no more d warning sinal on my screen..


  18. Ok with trying to spin the fan with a piece of paper.
    But I found it much easier, and even more effective, to just apply my mouth to the air intake and exit, and then blow as hard as I can. There were a couple of dust puffs coming out, then the fan started spinning again. A few seconds and it may work.

    • Did you take it apart? Or only just blowing as hard as you could on the exits for the fan!? I’m having the same problem! ;[ Thanks!

    • I have an even simpler solution. I had posted my old HP G6 to my friend but in transit the fan must have got jammed as the above error was displayed on switch on. I told him to switch the laptop on and while it was starting up turn it sideways then invert it while gently shaking it. Bingo!! the fan freed itself and the computer started windows successfully. So try this method before doing anything else.

  19. Hi! I also have a Compaq presario CQ56-106la. No mater how many times I clean it and change the silicone grease it still overheating. Any idea of this?

    The Fan spins very fast and all the vents are clean (in case if you ask me).

    Maybe a damaged/malfunction video can cause the overheating?

    Thanks in advance.


  20. Hi,before seeing your article, I had already taking apart the laptop exactly as described but after replacing with a new fan entirely, and new power battery then coupled laptop back, the laptop still won’t come on nor the fan roll. Please what is the likely issue or resolution?

  21. Great instructions bought the laptop fom a car boot for a tenner and got the fan error message when first turned on,i read your instructions, so first i blasted both fan intake and output with a can type air duster which i got from the pound shop, no luck with this, then with the laptop switched off tried spinning the fan a few times through the vents with a watch makers screw driver, when i switched on the laptop, straight away the fan could be heard spinning so now i have a fully working W7 500gb laptop for a tenner fantastic

  22. thank you very much i really appreciate but i have tried all every thing clean the fan yet the fan spine for only 15 seconds and stop.i got a fin of the same type of machine but it stop in 15 seconds.please what could be the problem.

  23. I have an even simpler solution. I had posted my old HP G6 to my friend but in transit the fan must have got jammed as the above error was displayed on switch on. I told him to switch the laptop on and while it was starting up turn it sideways then invert it while gently shaking it. Bingo!! the fan freed itself and the computer started windows successfully. So try this method before doing anything else.

  24. I am getting the message but the fan is working ok, but all credit to you for posting. Thankyou.

  25. Pingback: hp laptop the system has detected that a cooling fan is not operating correctly

  26. Thank you, the paper pin trick worked ut even if it would not, i dnt think so there would be any problem they way you have explained, sopcially with images. Thanks

  27. Stripped my computer right down and got rid of loads of felt like dust out of the vent and surrounding area
    Fan appears to be spinning normally but still getting message at start up

    • Hi, it could be that the fan has stopped working. Is there anyway you can put 5v to the positive and negative connector? 9v does work but not advised!

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