Got a 424i with a PRI , that the customer is complaining about a clicking noise on incoming calls randomly, I thought it was going to be analog extensions with MSG waiting lights bleeding over, went out and did #409 on all analog , reset CSU/DSU and PRI card and even had the customer power cycle after hours. Just got a call saying that it is still happening, not as often but they still hear it randomly, of course it didn't happen one time when I was onsite. Any thoughts

Do they have PDKU1's or 2's mate?

Could be an analog extension set to ring on an incoming call, or a fax extension.

Remember that it could be multiple MSG lights on any given extension. Try doing the extinguish code again, as you saying it lessened in frequency makes me think it's still analog ports. Also, they are the only thing I've ever known to make audible noise on a system.

If you think it's an MWI voltage issue then in prog 35 you can turn on LED 4 for all digital and electronic stations and turn off LED 3 for the analog stations. This should help prevent the analog stations from receiving a MWI. Or if you have an RSTU1A or PSTU1A laying around, swap it out with the xSTU you have in there now.

If it was the MSG waiting on analog wouldn't I hear it standing by the system??

Yes, you would hear the clicking. Is this problem system wide or just one station? Are the station(s) affected digital or analog?

All stations and all digital, and it follows the call if it is transfered, I think I will try and replace the PRI card if I have a spair

Sounds to me like it is a timing issue with the PRI. Have carrier run test on span, if you don't have a TBerd or anything like that

I have had faulty RSTU cards cause clicking on the system which could be heard on the lines as well.

Should probably swap out the PRI card as a precaution.

Clicking/ticking was a problem identified on PDKU1's which is why I asked if they were 1's or 2's. you can do a mod on the card or upgrade to PDKU2 which should resolve the issue.