Bravo panel dimmers not working

[toomany]

Not sure if this should be in modern mooney discussion or not, but i have an 89 bravo that has two dimmer rockers located in the panel on the co-pilot side (left knee area).  The panel lights behind the gauges and the lights located along the bottom edge of the glare shield are connected to these rocker switches and it appears as both have given up the ghost.  Does anyone know if there is an inline fuse or any other factor that would cause these switches to stop working - simultaneously?.  Panel and glare shield lights still function, however they are on the lowest dimmable setting.  Any input is greatly appreciated.

[PT20J]

Rocker switches or knobs?

[LANCECASPER]

6 hours ago, toomany said:

Not sure if this should be in modern mooney discussion or not, but i have an 89 bravo that has two dimmer rockers located in the panel on the co-pilot side (left knee area).  The panel lights behind the gauges and the lights located along the bottom edge of the glare shield are connected to these rocker switches and it appears as both have given up the ghost.  Does anyone know if there is an inline fuse or any other factor that would cause these switches to stop working - simultaneously?.  Panel and glare shield lights still function, however they are on the lowest dimmable setting.  Any input is greatly appreciated.

M20M through serial number 27-0107 had two black rocker switches - these are the exact ones (part number 7105-J1-Z-Q): (https://www.ebay.com.au/itm/X20-LOT-SWITCH-PUSH-MFR-C-K-P-N-7201-J1-ZQ-7201J1ZQ-ALT-939953-/312046917558). Later starting with serial number -0108 they went to knob rheostats.

There is a Light Control Box (Mooney part number 950D0307-000) where there is a simple circuit board. The Mooney Illustrated Parts Catalog says it's on the aft side of the Baggage Compartment. Someone good with circuit boards could figure out which component needs to be replaced.

[jcovington]

10 hours ago, LANCECASPER said:

There is a Light Control Box (Mooney part number 950D0307-000) where there is a simple circuit board. The Mooney Illustrated Parts Catalog says it's on the aft side of the Baggage Compartment. Someone good with circuit boards could figure out which component needs to be replaced.

@toomany. Attached is the schematic that I drew after the dimmer control panel failed on my 1996 M20J. I suspect it is the same control box as the M20M as the later Js share a lot of the same parts. The LM338K voltage regulators are what has failed on mine (twice). Pretty easy replacement if you have soldered on circuit boards before. The voltage regulators are mounted on the outside of the box but can't be removed until you open the box and desolder them. After that, remove the screws, put in the new and resolder. The cases on these voltage regulators are isolated from the case so don't lose the plastic washers.

Jim

Panel Light Board.pdf

[peterl]

On my 1991 Bravo the dimmer control worked only if the nav lights were 'on'.

[Fly Boomer]

1 hour ago, jcovington said:

Attached is the schematic that I drew after the dimmer control panel failed on my 1996 M20J

Is there a description of the connections (A1, A2, 12, 15, etc.)?

[jcovington]

1 hour ago, Fly Boomer said:

Is there a description of the connections (A1, A2, 12, 15, etc.)?

Those are the pin numbers that match the connector on the box. From memory, the connector is a DB-25 shell with some larger pins. The A1 and A2 are high current (large) pins. The other pins are fairly small (about 20 gauge or so). If you look at the connector on the box the pin numbers are marked (at least on mine).

Jim

[Fly Boomer]

3 minutes ago, jcovington said:

Those are the pin numbers that match the connector on the box. From memory, the connector is a DB-25 shell with some larger pins. The A1 and A2 are high current (large) pins. The other pins are fairly small (about 20 gauge or so). If you look at the connector on the box the pin numbers are marked (at least on mine).

Jim

Ah.  That makes sense.  I don't have the box in hand; I was just capturing the info for that fateful day.  Thanks.

[LANCECASPER]

3 hours ago, jcovington said:

@toomany. Attached is the schematic that I drew after the dimmer control panel failed on my 1996 M20J. I suspect it is the same control box as the M20M as the later Js share a lot of the same parts. The LM338K voltage regulators are what has failed on mine (twice). Pretty easy replacement if you have soldered on circuit boards before. The voltage regulators are mounted on the outside of the box but can't be removed until you open the box and desolder them. After that, remove the screws, put in the new and resolder. The cases on these voltage regulators are isolated from the case so don't lose the plastic washers.

Jim

Panel Light Board.pdf 39.34 kB · 4 downloads

The box and the part number of the box evolved over the years so for sure the 1989 box ( 950D0307-000) was different from the one used in 1996 (800299-501). Hoever the idea was the same so there are probably some similarities.

[jcovington]

1 minute ago, LANCECASPER said:

The box and the part number of the box evolved over the years so for sure the 1989 box ( 950D0307-000) was different from the one used in 1996 (800299-501). Hoever the idea was the same so there are probably some similarities.

Too bad it isn't the same. I agree that there probably are some similarities as the dimmer is just having to change the voltage to the lights. Not too many different ways to accomplish that.

Jim

[toomany]

thanks to all for the input - i'll get into the aft section of the aircraft and have a look at the lighting controller ASAP.  Thanks again - great forum!

[Steve Dawson]

@toomany were you able to get your problem solved? If it was your box how did you fix it? 

[rgpilot]

I had the same problem with my 2003 Ovation. I sent the box in the tail and the dimmer control box to Kenneth at International Avionics in Texas and he was able to fix the dimmer control box by replacing the two dimmer rheostats. He tested everything and returned it for$600,

It works perfect now,

[Guest]

6 hours ago, Steve Dawson said:

Toomany, were you able to get your problem solved? If it was your box how did you fix it? 

To page him you need @toomany

[LANCECASPER]

1 hour ago, rgpilot said:

I had the same problem with my 2003 Ovation. I sent the box in the tail and the dimmer control box to Kenneth at International Avionics in Texas and he was able to fix the dimmer control box by replacing the two dimmer rheostats. He tested everything and returned it for$600,

It works perfect now,

On an Ovation I used to own I had the same problem. In 2015 I bought two exact spec rheostats on Mouser and had a radio shop replace them. Back then it was $40 for the two rheostats and $50 for the radio shop.

[Steve Dawson]

Thanks Clarence

I had the same problem but lucked out with it only being a loose connector. 

[toomany]

i haven't had the time to try the first fix of replacing the voltage regulators on the outside of the box yet. i've gotten the v regs at the hangar - just no time.  

i'll look into the rheostats if the v regs don't do the trick.  

here's one for the forum - i was clearing a static line the other day and noticed the same controller under the dash on the pilot side - is this a lighting controller as well?  if so, what for?  why run wires the whole way to the tail for dash dimmers?  

[carusoam]

Mooneys have two traditional dimmers…

1) Instrument lights

2) Interior lights

 

No idea what goes to the tail regarding the dimming of lights… unless the baggage compartment light gets dimmed…(?)

Best regards,

-a-

[JimK]

My panel and glareshield dimmers were not working when I bought my Ovation 3 when I bought the airplane.  I disassembled the control box (mounted on the aft side of he aft blackhead of he baggage compartment) that others have talked about.  I found that someone had installed one of the voltage regulators backwards which allowed the pins to short out against the heatsink and that burned out one of the resistors on the circuit board.  I replaced the voltage regulators and resistor and it works fine now.  I have another post on Modern Mooney which shows a pic of the components.