Canon EOS 450D / Rebel XSi: How to repair the defective autofocus

A DSLR camera is a fine thing. My Canon EOS 450D (also labeled as Canon EOS Rebel XSi) gives me a lot of pleasure even with its standard kit lens Canon EF-S 18-55mm 3.5-5.6 IS.

After three years there has been the first defect now. During a mountain hike the autofocus stopped working.

This article outlines how I solved the problem for about $10. And even if your AF is currently still working, it may be interesting to you how to disassemble a Canon EF-S lens.

» Um die deutsche Version dieses Artikels zu lesen, bitte hier klicken.


Autofocus is dead. What to do?

At first I thought that my camera got too much splash water, but even some days later the autofocus remained dead.

Well, not all dead. If the focus was completely retracted, it was possible to focus exactly one time and then the AF was dead again. This meant that at least the focus motor should still be intact. I suspected the lens to be faulty, because everything was working perfectly when it was switched to manual focus mode.

So I tried a friend’s lens on my cam and behold: the AF was working! Now it was clear that my EF-S 18-55mm lens had to be defect.

I was already out of warranty for 1 year, so I had three options:

  1. Giving the lens to a repair center. Too cost-intensive.
  2. Buying the successor (IS II). Matter of expense: about $200.
  3. Disassemble the defective lens and have a look inside.

Since I had nothing to lose I decided to have a try with option 3. Fortunately, because today I hold the EOS in my hands and it’s working perfectly again with the old lens.

If you have a similar issue, the following may be helpful to you. Everyone with some manual skills should be able to reproduce it since no soldering rework is necessary.


Step 1: Disassembling the lens

It’s surprisingly uncomplicated to unscrew the lens if you are using a fitting miniature crosstip screwdriver (screws are tightened quite strongly).

It’s important to use a screwdriver with the right tip which is size PH00 in this case. Don’t work with the wrong tool, you won’t be happy.

At first you have to loosen the four screws on the backside and swing open the top cover. Carefully detach the flex cables (FPCs) from the white connectors. After that you can take off the controller board together with the top cover.

On the picture on the left the cover of the focus gearbox was also removed. This is not necessary and is not recommended! The whole gearbox unit is taken off as a single piece by removing the two silver screws.


Step 2: Replacing the defective FPC

As I had the lens disassembled so far, I immediately spot the broken flex cable which connects the focus position slider with the controller board. Bingo!

Apparently this is a fatigue failure as the FPC is bent and relaxed with every in- and out-move of the lens (during zooming, not when focusing!). Quite a questionable construction from Canon (keyword “planned obsolescence”).

If it is looking similar in your case, you can proceed as described below.

1a) Removing the broken FPC
On the picture in the middle, you can see the defective flex cable on the left-hand side (it only seems to be flexed sharply, but it is really broken straight through). In the background there is the silver slider which has to be removed now (in the picture on the left, the slider is top right). It is maybe a bit hard to unbolt the two screws of the slider. Afterwards the glued FPC can be removed with help of needle-nose pliers when the lens is fully moved out (i.e. maximum zoom).

1b) Ordering the spare part
Now it’s time to obtain the spare part. I got hold of a Canon spare parts list. Every single part of the lens is descripted there in an exploded view.

Fortunately, the broken FPC for the autofocus can be ordered as a single spare part. The part number is:

FPC Focus

You can obtain the spare part directly from an authorized Canon service partner. You find one through your local Canon website. Navigate to Consumer > Support > Product Repair and choose Digital SLR for the product type.

When you do not essentially want an original Canon spare part, you can get the flex cable quite cheap e.g. from eBay. Especially when ordering in China you may have to consider quite long shipping times.

1c) Mounting the new flex cable
The spare part comes with an adhesive film on its backside and can easily be attached to the right place, which is defined precisely by a rectangular deepening. Just remove the protective foil and patiently place the FPC with tweezers. The lug of the slim part leading upwards is also glued on. Be careful for the tappets of the lens body to lock into the holes of the FPC (possibly it’s necessary to bend the FPC a bit).

Finally the FPC should firmly be pressed down with help of cotton swaps or similar.


Step 3: Reassembling the lens

Now it’s nearly done. The reassembly is naturally done in reversed order:

  1. Screw the slider in place.
  2. Mount the focus gearbox with the two silver screws. Mind the long plastic axis to be locked into the short gear collet because otherwise the focus won’t work at all.
  3. Reattach all FPCs to the controller board. A toothpick maybe helpful doing this. The FPCs may be quite rough-running, they have to be inserted carefully and as far as possible. Insert the board into the lens body. Pay attention to the pictures and be careful not to break anything.
  4. Put the grey plastic ring on top (fits only in one single position) and screw the top cover in place with 4 screws.

Now it’s time for a first operational test. In my case the autofocus worked again straightaway (don’t forget to set the slide switch back to AF if necessary).



For me it was worth the effort. I’ve saved 90€ and my old lens is as good as new again.

I hope this documentation is also useful for some of you out there and I am looking forward to your comments. And please feel free to complain about translation mistakes. This would be a help for me, too.


Further reading

122 thoughts on “Canon EOS 450D / Rebel XSi: How to repair the defective autofocus

  1. Thanks so much for posting this! After 4 years my lens stopped focusing in one direction. I just did this repair tonight. My FCP was completely broken. With a good pair of tweezers, plenty of light, and some careful patience this very doable. Got mine working on the first try. Total cost including shipping was $9.98. Thanks for saving me a bunch of money!

  2. Another successful repair:-) ordered the spare part on eBay from 2012goelec which arrived 2 weeks later. Installed it in less than an hour and my lens has been repaired, ready for service.

  3. Thank for your post sir! work like a champ! Even though you aren’t recommended to remove the motor and gear box but i do find much easier when the motor is removed. as long as you know where is your focus lenses position, either all the way in or all the way out. this will help when re install the motor. costed me $9 for the part and 15 minutes of my time.

  4. Many thanks Marphy, it worked for me as well!

    Good tutorial with sharp pictures, helped me a lot. Spare part: $3 plus post+package: $17 = as a total a good deal 

    Two comments:

    – Bullet 1a) Removing the broken FPC: my screwdriver PH00 was too big for the silver slider screws, had to use a smaller one

    – Bullet 1c) Mounting the new flex cable: I agree with MacNB: The self adhesive film was tricky to handle, so I practised a couple of times first with the old one. I didn´t get the new to stick as good as the original, perhaps it picked up some grease but it works as of now. Hopefully the silver slider will help keep it in place.

    Thanks again, Google is wonderful! // Magnus from Sweden

  5. Just replaced focus cable but from 35mm to 55mm on the zoom it just seem to focus back and forth.Looking at the FPC Zoom cable there appears to be asmall crack in the cable YH1-2402-000.
    does anyone know were i could obtian one?

    • Lens is now working perfectly.
      Managed to get hold of zoom cable from H Lehmann (UK) couldn’t find any on eBay.
      Thanks for this tutorial saved me a few £££££.

  6. Thank you very much for this write up! Saved me lots of money just before Holiday:) Bought flexi off ebay for £3.60 in UK.
    All the best!

  7. Thank you very much. All works. Your method is the simplest, it avoid to unmount the front part of the lens like many others said. You are the best. Thanks again (from France).

    • Good tuitorial, mine had exactly the same issue and following your instructions fixed it perfectly for a few euro.


  8. Hi: I have a 450D and will not take pictures unless it is in auto. In the other settings I have shutter it twice. I have tried cleaning the contact and changes the lens but it makes no difference. Any ideas? Roger

    • Try another lens. If the problems still occurs, it’s probably the camera’s fault. In this case I have no other idea besides removing the battery and maybe doing a factory reset.

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