HELP AF error D700 24-70G combo

[Geomiljo]

OK, any ideas on this:

With the D700 / 24-70G combo the AF function sometimes just turns off... both the body and lens are from 2008, and the body has seen some abuse.... but the camera including the focus confirm light still works so in manual focus mode everything continues to function as normal.

The lens is as far as I can tell in perfect condition.

The quick fix is to turn the camera on/off, turn the lens in the mount a couple of times, and after a while, the AF is up and running again. Or of course using it in manual focus mode.

So I have tried the lens on my D800, no problem, and when using my D700 with other lenses, no problems....

Very difficult to reproduce the error, possibly it happens when the camera and lens have been in a warm car for a few hours.

Is there anyone out there who has experienced anything similar?

/Johan

[Andrea B.]

If it is the specific combination of the D700 and your 24-70/G only, then it sounds like there is some mismatch between the D700 lens mount and this specific lens. So attach the 24-70 and look for any signs of warping or other gaps. The 24-70/G is a somewhat heavy lens, so it is possible that the lens could "pull" on the D700 lens mount in a way not seen with other lenses.
Also, it never hurts to clean the contacts on both the body and the lens even though so far you have not had any problems with other lenses on that D700.

I've had the (old version) 24-70/G since it was introduced, but have not experienced any AF failures so far on D700, D3S, Df, D810 and now the D500.

Just thought of this:  Is the D700 firmware up-to-date?

[Bjørn Rørslett]

If you have a (small) JIS screwdriver, try tightening the two retaining screws for the contact block. They might have worked themselves a little loose over time and excessive play here in the block will create the errors you encounter.

[Geomiljo]

Thanks for the replies!!

I will try:

A) Cleaning (did think of this but turning the lenses on and off should be good enough I thought), will try with a little methanol.
B) Tightening the screws, not sure about the "two retaining screws for the contact block", but first found two screws on the mount that actually were, well, if not loose so at least not tight, so I have fastened these as much as I dare with my not so perfect screwdriver. See image. The bigger screw on the left, in focus?
C) Then I checked the smaller screws, see one of them on the right (not in focus), at both sides of the contacts, and they were also perhaps not loose, but could be tightened, so I tried as much as I dared....

The "cool" green light is due to the lens being in front of the computer, in the background the football game between Belgium and Scotland, my guess is that it is the green grass that is reflected in the lens....

/Johan

[Andrea B.]

And I'll mention this because I have done it myself on occasion:  Make sure the lens switch is on M/A and not on M. 

[Bjørn Rørslett]

Geomiljo: it's the smaller of the two screws. The bigger one holds the black stray light baffle, no harm in tightening that. Look two-thirs the way to the right along the contact block to find retaining screw #2.

The tip to check the AF/M switches on lens *and* camera should be followed up as well.

[Geomiljo]

So now I have tried fixing it.

First I just tightened the screws, but this enhanced the problem! Suddenly the same problem occurred with my D800, so it seems to be a lens problem.

But then after cleaning the contacts (on the lens) it started working almost normally! But still sometimes "sluggish", like nothing happens the first time I press af-on or shutter release button, but then the second time it´s OK.

Not completely logical since tightening the screws obviously had some impact on the system.

Contact oxidation?

Now I am just back from a small hike with the 24-70 on the D800 and it seems to work normally. All is good I suppose.

However....

It does make me want to know more about what´s inside the lenses... and how to fix problems.... I have a hard time trying NOT to get out the screwdrivers again and start taking the lens apart...

So at the moment I think that a NikonGear workshop "focusing" on lens and perhaps also body surgery would be a Great Idea!!!

/Johan

[Andrea B.]

It almost sounds like the contacts are not making good contact all the time. Is there any play at all between the lens and the mount when the lens is seated? Don't wiggle it too hard while checking this! 

[Hugh_3170]

Have the contacts inside the D800 been tightened and cleaned?

At face value, any such issues with the lens and its contact block sound as if they have been remedied.  One remaining possibility is that the small edge connector on the PCB ribbon that runs from the lens's contact block into the body of the lens has worked loose.  Checking this out is probably a technician job however.

[Geomiljo]

Well, I cannot feel any play between the lens and the body (D700 or D800, both feel the same).

Maybe it was a combination of a little dirt on the contacts and the contact block screws not being absolutely secure.

For the last two days the lens has been OK, so I`ll just have to wait and see what happens, I suppose.

Thanks for the help!

/Johan

[David H. Hartman]

It sounds to me like the body contacts on the D700 are the problem. Moving the lens from camera to camera can move a contaminate from one camera to the other. This could fool one into thinking that something else is the problem.

I hope the problem is resolved,

Dave

I don't recall problems with AF lenses, 2000 to date but I have had problems with a Nikon F100 back and MD-12 motor that cleaning cured. I used methyl alcohol, regent grade but alcohol isn't a proper solvent for wax so multiple cleanings may be required. I use Q-Tips cotton swabs and change them frequently. I believe that Chapstic lip balm was the problem with the MD-12. After several cleaning the MD-12 never failed again.

[Hugh_3170]

Johan, with the lens removed on your D700 (and your D800), does the internal camera body contact block with the 8 metallic pads seem loose and do these contacts seem dirty? 

If the internal contact block is at all loose, then it needs tightening and if it is at all dirty then it needs cleaning using a cotton bud with a little isopropyl alcohol.  These two conditions can occur even if the lens mount on the camera and the bayonet on the lens are both rock solid.

Well, I cannot feel any play between the lens and the body (D700 or D800, both feel the same).

Maybe it was a combination of a little dirt on the contacts and the contact block screws not being absolutely secure.

For the last two days the lens has been OK, so I`ll just have to wait and see what happens, I suppose.

Thanks for the help!

/Johan