Tester22

After a long delay, we were able to continue our troubleshooting today. My friend (A&P/AI) found a couple of butt spliced connections leading to the down limit switch. It appeared the limit switch had been replaced in the past. Two of the butt spliced wires were quite loose with one falling out of the connector. Reconnected the wires from the down limit switch in a more sano way and the system is back to working as designed. (N.B. The butt spliced connections were hidden behind cable wrap. Thanks for everyone's input, tips and ideas. I appreciate it. The site was a wealth of knowledge are far exceeded what the Mooney Tech Rep was willing to provide.

Thanks for the quick response. I’m assuming you mean you have to be a bit more careful during ingress and egress so as not to damage the inflatable seal, correct? If so, do you find it’s a bit more cumbersome getitng in and out with the seal installed?

Can anyone provide their thoughts regarding adding this mod? Benefits? Manual vs deluxe vs electric?

Skip, thank you for the additional troubleshooting tips. I appreciate it. The floorboard gear indicator light is NOT getting power with the gear down. I'll report back once we've had a chance to continue troubleshooting.

1. Yes 2. Yes And, correct, no Gear Down, Gear Unsafe nor floor position light regardless of physical gear position (up, down or in transit). We are scratching our heads…

Attached image is the old switch as installed. You can see the slot in the throttle cable housing where the throttle cable is able to actuate the switch.

Can anyone send a pic of their throttle microswitch? The switch that was mounted in mine is attached (two pics, red on one side, black on the other) Honeywell 1SM1-T p/n 480-2877-ND. This also corresponded to a cross-reference parts compatibility list on the Textron webpage. However, the Mooney tech rep advised that the microswitch is Honeywell 1SM1-T, (stock photo attached). The switch that was removed and replaced was rated at 15A@125V whereas the Mooney recommended switch is rated at 5A@125V as well the actuation force was higher on the installed switch vice the Mooney recommended switch, though I don’t see how either difference could impact continuity and operation. If the throttle mounted microswitch is showing 12V with the gear up and no voltage when the gear are down, and the Gear Warn CB shows power on both sides, does anyone have any idea what the next troubleshooting step should be?

We made some headway today. -The throttle mounted microswitch indicates 12V recevied whenever the gear are up; no power when the gear are down -The Gear Warn CB is showing 12V on both sides Both A&Ps are starting to supsect the belly-mounted gear down limit switch. There seem to be 5 wires that terminate at the switch. It’s not clear which wires coorespond to the Gear Down and Gear Unsafe WCAs as well as the FMGPI. Any insight would be appreciated. If the gear down limit switch needs to be replaced, do you have the wiring diagram and wire numbe codes? We cannot find a cannon plug or similar quick disconnect that would facilitate a quick remove and replace. Also, can you verify that the nute for the mounting bracket is in inside the fuselage and beneath the carpets? They’re guessing it may be located under the rear seat. N.B. While both A&P/AIs at my home field are very experienced, this is the first time that either of them has had to troubleshoot a Mooney landing gear issue. Thanks everyone.

Thanks for the input, everyone. The reference to the re-installation of the tach and manifold pressure gauges was proivded only to document the most recent maintenance that was performed. And, the work was performed BEFORE the gear issue manifested; not after, as I originally wrote. (N.B. the original post was editted to increase clarity.) The fact that the guages were installed next to the CB panel was of interest in that, perhaps, a ground or power wire had been dislodged. A Mooney tech rep provided both the gear wiring diagram as well as a simplified schematic, attached. Troubleshoting is ongoing. I’ll report back with the results. Thanks again. 2 GEAR DN LOCKED.PDF 800330_E1_email1.pdf

1978 Mooney M20J (Missile STC) TTA: 3718.8 Over the last 4 flights, when reducing power from a high throttle setting, the gear up warning horn would sound, sometimes when power was above 20 inHg As power was further reduced, the gear up warning honr would silence, usually around 18 in Hg of manifold pressure With further power reduction, the gear up warning horn would sound, usually around 15-16 inHg of manifold pressure The gear warning horn sounded twice (horn alert on, off, then on) on two of the last four flights Immediately prior to the gear inidciation issue manifesting, A&P installed a manual tachometer and engine manifold pressure gauge that I had had removed during an avionics upgrade two years ago Post maintenance check flight after the reinstallation of the gauges was nominal (all gear lights operated normally) Gear Unsafe WCA (Warning/Caution/Advisory) illuminated on the panel when gear were in transit Gear Down WCA illuminated once the gear were fully down and the Gear Unsafe WCA extinguished at the same time The floor mounted gear position indicator (FMGPI) indicated gear down and the backlight under the plexiglass was illuminated During the next flight (2.0 hours) none of the lights illuminated when the gear was lowered No gear unsafe WCA, no gear down WCA, no backlight in the FMGPI The actual gear position off the FMGPI indicated gear was down (two black lines aligned as normal) Waived off, entered the overhead delta, retracted the gear No gear unsafe WCA, the FMGPI indicated the gear were up All CBs were in Emergency gear handle was stowed and locked Instrument panel dimmer switch was off In the overhead delta, I once again lowered the gear Runtime of gear motor and mechanical thunk were consistent with gear down and locked However, the Gear Unsafe WCA did not illuminate while the gear were in transit and the Gear Down WCA did not illuminate once the gear were down nor did the FMGPI backlight illuminate FMGPI indicated gear were down (two black lines aligned) Landing was uneventful A&P and I inspected area around the engine tachometer and manifold pressure (installed just to the left of the CB panel) No loose wires Noted 7 of 8 round wires attached in the vicinity of the upper glare shield cross brace (just to the right of the center panel mounted upper avionics stack) Same as when we commenced the installation of the gauges Put the aircraft on jacks Lowered the gear Noted no power to FMGPI backlight With the gear down and locked, A&P wiggled one of the wires attached to the throttle mounted microswitch Gear Down WCA illuminated and FMGPI backlight illuminated Raised the gear Gear Down WCA extinguished Gear Unsafe WCA posted while gear was in transit FMGPI light extinguished Lowered the gear; all three lights worked as they should Wiggled the wire again and the Gear Down WCA and FMGPI backlight extinguished A&P thought the connector was loose inside the throttle mounted microswitch Replaced throttle mounted microswitch with PART: 480-2877-ND DESC: SWITCH SNAP ACTION SPDT 15A 125V MFG : HONEYWELL SENSING AND PRODUCTIVITY SOLUTIONS / V3-1 from DigiKey.com All gear lights were inop regardless of gear position It was quitting time so we couldn’t even wiggle some wires Does anyone have any idea what may be happening? Does anyone have the wiring diagram for the circuit that includes the throttle position microswitch, gear WCAs and FMGPI backlight? Any thoughts and insights would be appreciated.