Troubleshooting Potentially Bad Cable

It appears that one of the four RG6 cables from my 5 LNB dish is bad. It is mounted on the exterior wall of a detached garage. The four cables run inside the garage around the perimeter to a conduit at the front where they go underground for 25 feet to the side of the house for distribution at lengths up to 80 feet.

I think a little history will help explain my situation.

My original SD TiVo used the two original cables from my first dish without problem for four years. One of these now appears to be bad. Two years ago an electrician friend pulled two more cables from a three LNB dish to the house to allow the use of an HD TiVo. The SD TiVo was moved to the bedroom but only had one line as one of the cables from the house distribution site to the bedroom appeared to be bad. I tested it in a third location and both lines worked. (This is a second bad cable that I intend to leave alone due to inaccessibility in the house.) I used one of the original cables from the dish for the SD TiVo. I used the newly pulled dish cables to connect to the two distribution cables used for the living room HD TiVo.

In May the TiVos were replaced with two HR21s. The install was painless. The biggest issue was removing the old dish from the roof of the garage and installing the 5 LNB dish on the wall. When I told the installer that only one cable to bedroom unit worked, he commented that one of the four cables from the dish was also bad. I did notice recently that one cable from the dish uses a barrel connector after running halfway down the support arm. This cable is tie-wrapped to the support arm.

I recently purchased an SWM8 to try to have two lines available for the bedroom HR21. It worked except I wasn’t able to get some channels. One was the local San Diego ABC affiliate. HBO was fine. I returned to the old setup and everything was fine except for having only one line to the bedroom HR21. Both HR21s see all satellites. The signal strength is good. Channels 480, 481, and 490-494 find the satellites on both HR21s. When I connected the cables from the dish that usually go to the bedroom cables to the living room cables, it worked fine except that only line 1 worked. Signal strength on line 2 was 0. When I swapped the cables, the receiver got stuck on acquiring guide data. Returning to the old setup and everything is fine. No multiswitches are involved.

After that long background my question is whether there is anything else I should check before having another cable pulled from the dish through the conduit to the side of the house? Is there any way to use a SWM8 with three rather than four lines? Assuming I need to have a new cable pulled, I’ll have my electrician friend pull it. He doesn’t know anything about Directv installations. Any suggestions on what he should be careful about doing and not doing with the 5 LNB dish would be appreciated. What cable and speed rating should I buy?