400 won't focus with IS off - Help

I picked up a used 400 2.8 IS off FM over the weekend and received it today. Got a chance to check it out this evening and everything seemed fine. Glass is clean, IS is working, AF is accurate, fast and smooth. However, I then turned the IS off and the lens won't even try to focus. I can hear it clicking inside, but nothing happening. This only happens WITH THE IS TURNED OFF. This is a problem as the lens will likely live on a gimbal and I need to be able to turn the IS off.

Date code on the lens is UN and I assume Canon would still service it as they just upgraded. However, not sure I want it serviced or if I want to send it back. Given what the 400s with slightly newer date codes are going for, I got what I feel like is a pretty good deal.

Anyone have this happen before? Is there something I am missing (not my first super) or is ther a legitimate problem here?

Also noticed with the lens attached and IS on, camera body operates fine. With IS off, the top LCD starts to flicker and LV won't turn on.

Thats odd, maybe something to do with the pins? If it were me and I just bought a lens that costs as much as that one does, I would probably send it back. Can't imagine anything on that lens is cheap to fix. Not to mention it's hard to imagine the seller didn't know the issue and thats why the price was so attractive.

Have you tried the lens on a different camera body?

I do not have a second body to try the lens on, but can probably find one and do it today.

The seller and I have been in communication and he swears there were no issues when he shipped the lens out. Even said one of the sample pictures he posted with the sale was taken on a tripod with is off and AF working (picture of the moon, so I believe him).

These body/lens combinations are quite complex. Just because the buyer has an issue doe not mean the seller had an issue. It is entirely possible the lens worked perfectly for the seller and differently for the buyer. We don't even know if the seller was using a 7D...

If the lens is the Canon EF 400mm f/2.8 L IS USM the IS version installed in this lens is tripod-sensing so turning it off is self-defeating. The lens knows that a tripod is likely being used when vibrations go below a certain level. Canon recommends leaving the IS turned on when mounting this 400 on a tripod to take advantage of the IS mode 2, thus reducing mirror slap, shutter and tripod vibrations. There are two IS modes, mode 1 and 2, which is for panning (stabilization in vertical only). IF that is the lens you are using, some time with the manual might be worthwhile.

John from PA wrote in post #14895541
These body/lens combinations are quite complex. Just because the buyer has an issue doe not mean the seller had an issue. It is entirely possible the lens worked perfectly for the seller and differently for the buyer. We don't even know if the seller was using a 7D...

If the lens is the Canon EF 400mm f/2.8 L IS USM the IS version installed in this lens is tripod-sensing so turning it off is self-defeating. The lens knows that a tripod is likely being used when vibrations go below a certain level. Canon recommends leaving the IS turned on when mounting this 400 on a tripod to take advantage of the IS mode 2, thus reducing mirror slap, shutter and tripod vibrations. There are two IS modes, mode 1 and 2, which is for panning (stabilization in vertical only). IF that is the lens you are using, some time with the manual might be worthwhile.

Actually, his sample pics were all from the 7d. The manual, which I have read previously with my 500, specifically say on page 11 to turn the IS off when on a tripod to conserve battery power. This is what I always did with my 500 and never had any issues. While it does have the tipod sensing system, I've found that leaving it on creates more issues than it helps so I turn it off - however, I digress.

I spoke with Canon this morning who said that the cost would likely be well under $500 as it sounded like a simple short of some kind. I'm gonna test it on another body shortly and go from there.

I was referring to the lens manual, which explains the differing IS modes (1 & 2) of the specific lens, Canon EF 400mm f/2.8 L IS USM. If that is not the lens you are referring to then perhaps it best to turn IS off. In the lenses made by Canon in perhaps the last 5 to 8 years, the lenses themselves are designed to detect two planes of motion. If the vertical motion is extremely small and their is some horizontal motion, then an algoritm determines that the camera/lens is likely on a tripod, so it has the capability of shutting down any IS corrections applied to the vertical plane. Even in the manual Canon recommends turning IS off on a tripod, but I think most people find mode 2 to be useful.

I've attached the manual which may prove helpful.

In most of the lenses if you rotate the body to a portrait orientation this feature won't work, so IS should be turned off.

John from PA wrote in post #14895894
I was referring to the lens manual, which explains the differing IS modes of the specific lens, Canon EF 400mm f/2.8 L IS USM. If that is not the lens you are referring to then perhaps it best to turn IS off. In the lenses made by Canon in perhaps the last 5 to 8 years, the lenses themselves are designed to detect two planes of motion. If the vertical motion is extremely small and their is some horizontal motion, then an algoritm determines that the camera/lens is likely on a tripod, so it has the capability of shutting down any IS corrections applied to the vertical plane.

In most of the lenses if you rotate the body to a portrait orientation this feature won't work, so IS should be turned off.

We're on the same page - I was talking about the lens manual. Tested it on 2 other bodies this morning and talked with Canon. They are pretty sure it is an electrical issue with something having poped lose.

Now, it's up to the buyer how he wants to proceed.