"Barry first let me thank you for spending the time to help me out!"
If you're sure that the remote works with the Rev. L TIU, then the problem is definitely with the old TIU and not the remote. If you've reseated the TIU's transceiver board and that did not resolve the issue, I'm at a loss as to what could be the problem other than a defect in the TIU itself.
Both remotes work fine with the Rev. L TIU so I am assuming the old TIU is defective from new in the box.
Where is a good place to send it for repair?
What happens if you press "READ", both while
Untethered=TIU address not found
Tethered= Found TIU address connected
As an aside, what software level is the new remote? It will briefly display this when you turn it on. 4.20-2003 old remote is 2.21-2002
Also, you should learn the Rev. L's software level by pressing:
Menu/System/TIU Setup/TIU Version=04.20
Thanks again!
charles