Gear down - doors stay open, pump running

[RandyArizona]

337 parts manual, figure 125, item 11:

MS28775-014

One on each solenoid is required.

[Joes]

Randy, thanks you do a good job with the details. Your a lot alike some of the older guys on this site that have now passed. Very detail oriented, keep up the good work with all the others we currently have.
Joe

[RandyArizona]

Thank you sir,
I believe details and facts matter, much more than "my opinion".
Oddly enough, I have been told, that I am rather.. "Rude"? No, "spicy" was the term.
When dealing with aircraft that HAVE to be correct, facts matter.
Have a good day.

[Learjetter]

Welp, after cleaning solenoids and running the gear several times no problem…there is a problem.

No obvious hydraulic leaks. Adequate hydraulic fluid level in reservior. Using additional 24v ground power, not just ships battery.

Gear retraction is normal.

Gear extension is normal, but doesn’t “complete” in the prescribed time of 13-16 seconds. What we’re seeing is normal extension, followed by no green light until after about 20-30 seconds total pump run time. In flight or on jacks, same results.

I’ve read the service manual and examined the wiring diagrams. I’m thinking it could possibly be one of the power pack pressure switches?

[RandyArizona]

If the gear "falls" uneven, it is air in the system which is difficult to get out.
(Just a pain to do., not hard)
How much extra 24 volt ext power?
The gear motor is a heavy draw, so turn off any and all electrics, not attached to the gear.
If the motor is old.. (which is probably, yeah.), the motor may be tired, and need a rebuild.
Do all of the locks "click" closed, and then the pump runs for another 20 seconds??
This system is troublefree- until it isn't.
Good luck.

>>>>>EDIT: I just read that the doors have been deleted from this aircraft.. I've never done one with the deletion mod. Take what I posted above with a grain of salt.<<<<<<<

[Learjetter]

Gear falls fairly evenly and all the locks click solidly. Less than 1-2 seconds between L and R gear locking down. I’ll add one more symptom I just remembered.

After flight Saturday AM, I towed the airplane and put it in the hangar. Several hours later I turned on the master switch to close cowl flaps, and immediately noticed the gear warning horn ON, and no green light.

I stood dumbfounded for 5 seconds then horn quit and green light came on. Pump never turned on.

External power source is either a 24v 20A power supply, or a 24v truck starter unit powered by capacitors. Both work OK to ensure solid 24v with plenty of amps is available to pump. I think.

UPDATE: smoking gun found! Went to airport today and by chance a couple buddies showed up. With all three of us, we jacked her up and ran the gear. Once retracted, I check F and R throttle switches and R throttle switch did NOT set off horn. Then we put the gear down and all gear went down but no green light and HYD pump continued to run. We then tested each gear downlock switch and found L MAIN gear down micro switch (S2088-1) intermittent and then it failed completely showing some 800+ ohms when closed.

Textron has switches in stock ($200 ea). Those little switches are quite fiddly to get out.

Plan is to replace bad switch, check function, and then fly a couple trips. Over the holidays I’m gonna tackle rebuilding every hydraulic cylinder in the system and probably replace hoses (quote from PHT was $1400 for all hoses). Next year, I’ll tackle th power pack itself.

Update 2: installed S2088-1 downlock switch, swung gear a few times, no defects noted.