The International Cessna^® 170 Association

Has anyone had trouble with their Mark 12 DC upgrade radio (for the ARC RT-300-328 radios) intermittenly running the Cessna CDI both in VOR and LOC mode and identing the station? If so, how did you fix it? Thanks.

I might be able to help.

What do you mean by “intermittently running the Cessna CDI both in VOR and LOC mode”? Do you mean that the CDI has an intermittent off flag? Are you getting the off flag in conjunction with the inability to ident the station? Or can you never ident the station. It sounds like you have several issues. Is this a new installation or are you replacing just the radio and using the old harness and rack? This information is critical as to where you start trouble shooting, but the first thing you need to check is that you have good power and grounds.

The "OFF" flag is on anytime the receiver cannot ident a station or LOC. I am using the original ARC RT-328 tray, plugs and CDI. It is a used unit yellowed tagged from Narco in 2004 and not used until I bought it two years ago. I talked to Narco technical and told them the problems I am having. They seem to think it is a cold solder or a "cap" problem of some sort. I have tried it in a friends plane with the ARC RT-328 tray, etc. (same as mine) and he had the same trouble. The Comm part of it works just fine tho. I am ready to ship it off to them and have them check it out unless you have some other ideas. I have cleaned the contacts on the radio back as well as the tray plugs. When it's working it works very well.

If you have any ideas please let me know ASAP as I have some trips coming up and would like to have the use of the Nav portion of the radio being trustworthy.

Thanks.

jT

I have had very good service from Narco factory on fast-turn repairs. They can usually get it done and back in your hands in 3 days, and they may also have a "rental" or "loaner" unit for your use in the meantime.

It sounds like the unit needs to go back if it exhibiting the same issues in another airplane and the existing hard ware was working with your old unit.