NARCO MK 12D Trouble Shoot

AdamZ

AdamZ

Touchdown! Greaser!
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Feb 24, 2005
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Montgomery County PA
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Display name:
Adam Zucker
My Nav/Comm 2 is a NARCO MK 12D. Sunday I flew a 220 mile RT in our bonanza. On the way back I stopped a f field about 30nm away from the home field to get some fuel at a good discount from what I could get at home. On take off after getting fuel I tuned in my Comm 2 to my home field's AWOS. When I hit the button to switch it from standby to active it just reverted to the previous freq in the window. I did it like 2 more times and same thing then the display just showed on vertical red LED cathode line , which was like the lower half of the numeral 1 on the left side of each screen ( standby and active) We shut the unit down. When we landed at home we fired it back up and same thing so shut it off again.

A couple of years ago we sent it out to Bevans to have the face repaired as some of the numbers weren't appearing correctly.

Any ideas would be appreciated. Will bring it out to our avionics guy at the next opportunity but wondering if it is a lost cause or there may be an answer.
 
The 12d (and the d+ is even worse) is an incredibly unmaintainable piece of junk. We had a plane grounded regularly by that in our flying club. You can't operate out of a class B primary if the radios don't work.
 
flyingron said:
The 12d (and the d+ is even worse) is an incredibly unmaintainable piece of junk. We had a plane grounded regularly by that in our flying club. You can't operate out of a class B primary if the radios don't work.
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Flyingron, I’ll tell ya that has not been our experience. We have had the plane for about 7-8 years and other than the LED’s burning out( which also happened on our JPI700 ) we have never had an issue until this. But as they say it wasn’t a problem till it was a problem.
 
I have two 12D+ that have been very reliable. Just recently had a display go bad and due to long lead times on new Garmin Nav/COMs I repaired it. Mikes Avionics had it diagnosed repaired and back to me in a week. I’d highly recommend sending it to him. At the time Bevans told me it would be 6-8 weeks before they could look at it.
 
BrianM said:
I have two 12D+ that have been very reliable. Just recently had a display go bad and due to long lead times on new Garmin Nav/COMs I repaired it. Mikes Avionics had it diagnosed repaired and back to me in a week. I’d highly recommend sending it to him. At the time Bevans told me it would be 6-8 weeks before they could look at it.
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@BrianM - Can you share a link for Mike's? Thanks!
 
flyingron said:
The 12d (and the d+ is even worse) is an incredibly unmaintainable piece of junk. We had a plane grounded regularly by that in our flying club. You can't operate out of a class B primary if the radios don't work.
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Yes. They were horrible. Troubleshooting a Narco MK12D means that when you have trouble with it, you take it out and shoot it.
 
Welcome to electrical issues in composite aircraft. Most of the time it’s a ground issue.

According to the DA 40 manual.
The voltmeter displays the potential on the main bus. If the alternator is operating, the alternator voltage is shown, otherwise it is that provided by the battery.

The ammeter displays the current with which the alternator is being loaded.

The alternator warning light illuminates on alternator failure. The only remaining source of electrical power is the battery. The color is red.

The low voltage caution light illuminates when the on-board voltage drops below 24 Volts. It goes out again when the voltage exceeds 25 Volts. The color is amber.
Possible reasons are fault in the power supply or too low RPM.
 
Clip4 said:
Welcome to electrical issues in composite aircraft. Most of the time it’s a ground issue.

According to the DA 40 manual.
The voltmeter displays the potential on the main bus. If the alternator is operating, the alternator voltage is shown, otherwise it is that provided by the battery.

The ammeter displays the current with which the alternator is being loaded.

The alternator warning light illuminates on alternator failure. The only remaining source of electrical power is the battery. The color is red.

The low voltage caution light illuminates when the on-board voltage drops below 24 Volts. It goes out again when the voltage exceeds 25 Volts. The color is amber.
Possible reasons are fault in the power supply or too low RPM.
Click to expand...

Thanks but the Bonanza is not composite.
 
Clip4 said:
Welcome to electrical issues in composite aircraft. Most of the time it’s a ground issue.
Click to expand...
That MK12D+ display is not related to voltage. It's related to quality. We bought several of those radios in the 1990s for the flight school airplanes, and every one of them suffered repeated display failures. Within about four years we had spent more on repairing them that they had cost in the first place. Junk.

An avionics tech showed me what he found inside them. Many had little "daughter boards," small circuit boards with a few components on them, wired into the main board, to fix performance issues that appeared during testing when brand-new at the factory. Disgusting. This daughter board stuff did not show up in any Narco schematic.

Nobody mourned Narco's bankruptcy, except maybe the folks that had a panel full of the stuff.
 
Totally fixable but unfortunately probably not as cost effective a replacement King. I just looked into having one repaired and it was gonna be $550 PLUS parts. Not saying that isn’t reasonable, except for the fact the rest of the parts are old and susceptible, meaning likely another $550 and parts in a year or two.

I bought an old Garmin gps/comm for $1000. The gps gives me a green line to about anywhere with an outdated database, which is cool, I’m VFR and using an iPad. The comm should be pretty reliable.
 
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