Focusing problem with Nikon 18-70mm

mutti_wilson

I had a problem with the zoom (stuck between 24-28mm) and found out online that a screw has a tendency to get loose on these lenses and needs to be tightened. I figured what the heck since it's a backup that I don't use much. I found the screw and everything went back together fine, but now the focus will not lock. The AF light comes on in the viewfinder when it is focused, but the lens just goes from limit to limit and will not stop. I can use it for MF and it works fine, but AF would be nice.

Anyone have any ideas?

ziggy53

It appears that the Nikkor ED 18-70mm f/3.5-4.5G AF-S IF DX can have anywhere from 1 - 4 screws loose to cause the problem that you describe (loose screw affecting zoom range.) If the elements and groups get out of alignment, it apparently takes a tool to re-align everything before tightening.

I suggest that it is time to find a competent shop or to return the lens to Nikon service. Repairs will probably run from $100-$200, depending mostly on who does the repair.

Edit: You might try these procedures (at your own risk, of course) for re-alignment:

http://irvdabird.multiply.com/journal/item/2/Nikon_AF-S_DX_Zoom-NIKKOR_18-70mm_DIY_Fix

Wil Davis

Found this thread, and decided to check my backup 18-70 zoom, (hardly ever used these days) but discovered that it shows the same symptoms as Ziggy describes.

Spent 30 mins with it, and lo and behold! No more sticking! A bit of a bugger to realign though! Gotta have much patience (plus a beer or three )

Thanks for the link!

Ziggy, you're a star!

- Wil

ziggy53

Wil Davis wrote:

Found this thread, and decided to check my backup 18-70 zoom, (hardly ever used these days) but discovered that it shows the same symptoms as Ziggy describes.

Spent 30 mins with it, and lo and behold! No more sticking! A bit of a bugger to realign though! Gotta have much patience (plus a beer or three )

Thanks for the link!

Ziggy, you're a star!

- Wil

I love a happy ending. Thanks for sharing.

mutti_wilson

Thanks guys. I've taken it apart and reassembled once more tonight with the same results. Here is a video of it focusing.

http://www.youtube.com/watch?v=piyYNdQ8ORY

ziggy53

mutti_wilson wrote:

Thanks guys. I've taken it apart and reassembled once more tonight with the same results. Here is a video of it focusing.

http://www.youtube.com/watch?v=piyYNdQ8ORY

The way the lens is hitting the hard stops I would bet that it is still misaligned. If you can't solve it yourself I suspect that a repair service with proper alignment experience and tools should be able to align it.

mutti_wilson

I brought it in earlier today and they quoted me $150.00 to fix it. That's nearly the value of the lens so I'm gonna work on it myself:)

When you are saying alignment are you refereing to the SWM motor fingers grabbing the focus tab or...?

Regardless, I'm going to tear it down again:)

Wil Davis

I followed the instructions found in the link which Ziggy posted. I had no problem in tightening the 3 screws (one of which was about ¼ turn loose). The problem I had was getting the two sleeves to mesh, and the outer sleeve to register with the main body, simultaneously; very tedious and frustrating. Each time I got the two sleeves set up, then I'd get the outer sleeve almost in the correct place, and then notice that the two sleeves were no longer meshing… (…repeat ad nauseam!!!)

I never fully disassembled the lens.

After the fix I did some tests with both my D70 and D300 and the auto-focus still seems to work perfectly.

HTH -
- Wil

PS: Before I tightened the screws, the lens would zoom OK, but there was a marked resistance at the 24-18 point, and occasionally it would stick at that point; now it's smooth throughout the complete range.

ziggy53

mutti_wilson wrote:

I brought it in earlier today and they quoted me $150.00 to fix it. That's nearly the value of the lens so I'm gonna work on it myself:)

When you are saying alignment are you refereing to the SWM motor fingers grabbing the focus tab or...?

If I understand the design of the lens it is a rather complicated dual cam design. The front element is also somehow linked to the screws which can loosen. Getting the whole assemblage back into optical alignment can be a problem.

I doubt that the AF motor linkage is changed unless you dismantled the lens further than needed for just the loose screws.

alexf

It happened to me a couple years ago. I took it to Nikon approved repair shop and they did an excellent job (tough a tad expensive). I went for it as I love the lens, I have a good copy and it is my light for travel lens. Has been working fine ever since.