an issue with my 70-200 f4is

Hi folks.

i am having a sporadic issue with my 70-200 f4is and I wanted to "pick your collective brains"

i bought it used about 1 year ago and it worked very nicely up until 6 months ago when I had a single issue that the AF mechanism didn't hit at all...it moved but there was no focus in the least. I tried removing the lens and replacing it multiple times. I looked at the contacts and it was all clean... so i changed lenses and those worked well. When I got home, I retried the lens and it worked perfectly.

Even so, I took it to the local canon dealer and after their exam - they said everything worked perfectly. I was happy.

Now in the last couple of days it happened a couple of times. I cannot isolate what i did differently. It allowed me to focus manually. I checked all the switches and the subjects were about 2-4 m away from me at different shots...I removed the lens and used a different lens...and then returned to the 70-200 and it worked again.

It is too expensive to return again to the canon dealer for a "nothing" complaint and I always leave my body with them for them to check as well... so if i don't have to....

I would appreciate any ideas or directions...

thanks

so....no one?

What do you have the focus limiter switch set to?

Have you tried to replicate the same focus issue with a different body?

Try setting your 7d to 'allow' focus hunt, set to ai servo, and see if it will af. Also check your limiter switch. I've had a few cases where it refused to focus because it had already tried to obtain focus I had the focus hunt off. Also I'd be too close to something without realizing it and again the focus hunt function would stop the camera from focusing.

thanks all for the ideas, I will check them at home (i am at work currently)
in regards to the extra body - that will be more difficult...and even more problematic when i consider that it is sporadic.
IIRC the focus limiter was moved in all the positions during the couple times - just to see if it affected - it didn't.
not sure what the reply of munizdanel1 meant....

thanks though for all your reponses and thoughts

Yeah any intermittent issue in electronics are tough to diagnose