M20M Bravo ASSS Issue, not preventing Gear Retraction

[Flynic3]

Good Afternoon,

I have an M20M Bravo in our shop finalizing an Avionics install and annual inspection.  During the landing gear testing sequence we experienced gear retraction even when airspeed was less than 60knots indicated, and even when at zero airspeed.  During further inspection of the ASSS we found that A/S#2 CPC connector was missing, and replaced with a 2 pin molex, along with the Yellow wire lead being capped and stowed.  It seems as if this portion of the ASSS has been incorrectly altered and essentially disabling this system to prevent gear retractions while on the ground.  I am attempting to correct this issue but having a devil of a time with tracking down what needs to be connected to the Yellow wire lead.  The full electrical schematics does not specify the wire label connecting to what should be Pin #2 of A/S#2 CPC.  This lead is connected to the NO portion of the relay with the Yellow, Green and Black wires.  It also looks like the NC portion of this relay is connected to ground when the Green wire should be.  The main Electrical Schematic references RC04A however when digging deeper, I am still not finding adequate leads on what this portion of the ASSS needs to be connected to.  This Mooney has the gear safety bypass switch, so I am really not understanding why the ASSS was altered in this manor...

I was curious if anyone had better wiring schematics for this specific ASSS system, as I have not had much luck with finding one.  It does appear as though AS#1 CPC is intact and was not messed with... the 3 wire bundle with the Red, White and Blue leads.  I did find a schematic for a different serial number range showing the Yellow wire lead connected to DM06A20 which I think is the output signal wire from the Hobbs.  That being said, the schematic for my specific serial number does not give that information.  I would assume that I will need to recreate AS#2 CPC with the Yellow wire connected to the correct wire lead along with the Black wire and switch the ground to the Green wire instead of the Black.  I just could really use some guidance of the wire labels connected to Yellow and Black wires of the ASSS.  If anyone has better knowledge of the ASSS system, it would be greatly appreciated!  

[PT20J]

It’s pretty simple. There are two switches on the airspeed safety switch. One is used for the gear system and the other is either unused or connected to some ancillary device such as an air Hobbs or flight timer. I don’t have your schematic, but for my M20J, the switch used for the gear uses the white, blue and red wires. The spare/auxiliary switch (not used for the gear at all) uses the yellow, black and green wires.

From your description, it sounds as if the auxiliary switch was used for something at one time that may no longer be installed. The problem with the gear is either in the wiring to the other switch or a bad switch. 

Skip

[Flynic3]

Good Morning Skip,

I greatly appreciate the quick reply and for the insight provided in your post... it is greatly appreciated.  I will further diagnose the Red, White and Blue side of the ASSS circuit to determine if we have a bad switch, or a wiring issue.  When I saw the way the Yellow, Black and Green side of the ASSS circuit was altered, I assumed this may be our problem.  I would still prefer to have things repaired to what the Mooney factory schematics specify to prevent future issue's.  That being said, based on your comments above I will focus on diagnosing the Red, White and Blue portion of the circuit along with the ASSS itself.  It does appear that this portion of the ASSS has not been altered and is intact.  If it does come down to replacing the ASSS, it appears as though this is a bit of a challenge as well... but will cross that bridge once we get there.  Thanks again for all your insight and assistance... I truly appreciate it!

PS. The Schematic for this particular M20M is 800304 Rev. AA... Serial 27-0232 thru 27-0239 and I have attached it below.

 

Best Regards,

Nic

Mooney Wiring.pdf

[Flynic3]

Attached below is the ASSS portion of the Schematic that I was referencing in my original post... which leaves a lot to be desired when it comes to the Yellow, Black and Green portion of the ASSS circuit.  It appears as though the Red, White and Blue side of the ASSS Circuit is going to the Gear Control CPC Pins 3,5,7 from Pins 3,2,1 on A/S#1 CPC.  I just wanted to post additional information about this aspect in case it would assist another Mooney owner in the future.  I read quite a few threads about this issue, and thought it may provide further detail for future use.  That being said, I have noticed a lot of differences on the schematics based on the serial number... when it comes to wiring and CPC labeling... so it may only be viable for the specific serial number range that I am working with currently.  The overall systems seem to be similar though, so it may at least provide a decent base line... and I hope it will help!

Best Regards,

Nic

[Flynic3]

Good Afternoon,

After further diagnosing this issue we have found that all of the Red, White and Blue wiring coming from the ASSS match the schematics and has continuity... the leads are also pinned to the correctly labeled A/S# 1 CPC and corresponding wire labels are also correct.  I am moving further downstream to the Gear control CPC to check continuity going to the A/S#1 CPC.  I have not found anything to indicate a wiring issue thus far, and everything matches the Mooney Schematic but the Yellow, Black and Green wire leads.  I was curious if anyone has ran into issue's with the ASSS Bypass switch constantly overriding the output from the airspeed switch.  I am more or less wanting to determine if there could be any other root causes beyond just a faulty ASSS.  I just do not want to spend $1,400 and wait a month to receive a new ASSS, only to find out that it was not the Airspeed switch.  What would be the best way to diagnose whether the ASSS itself is faulty?  I spoke with the guys at World Magnetics and their VeP engineer stated that I just need to verify the wiring leads matched the schematic and were connected to the correct wiring labels from the CPC.  I would just prefer to be a bit more thorough in the diagnosing of the ASSS, prior to telling the customer we need to replace it.  I would love to know if anyone has ran into other issue's with this system, beyond a faulty ASSS... and whether the ASSS is usually the culprit.  I greatly appreciate any insight and assistance you may have in this matter!  

Cheers,

Nic

[Flynic3]

Good Afternoon,

I wanted to post a follow up to my previous posts after further diagnosing the ASSS in this M20M Bravo.  We found the ASSS to in fact be faulty and the easiest way to do this is relatively simple.  The VeP 654-34 is essentially a diaphragm with two microswitches and the easiest way to diagnose whether the ASSS is faulty is by checking Continuity between the blue wire (Pin #2) and red wire (Pin #3).  If you have continuity between these wires without 65knots than the ASSS is faulty.  You should normally have continuity between the white wire (Pin #1) and red wire (Pin #3) when you are on the ground and airspeed hasn't reached 65 knots.  It is as simple as that, and after chasing the rabbit down the hole further than I would have liked to, I realized I was over complicating things.  I hope this may help another Mooney owner who has experienced this issue with the gear coming up without the adequate airspeed.  I am curious why a simple pressure transducer wasn't used instead, as it seems this would be a much more reliable system compared to the Diaphragm and microswitch arrangement.  Regardless, I just wanted to provide further insight into the ASSS and hope it saves someone the hassle in the future.

Cheers!

Nic