rear cowl flap motor issue

[B2C2]

Hi. I have looked through the forum and understand this is a known failure mode for this airplane. On my 1969 T337D I was preparing to leave Carlsbad on Sunday but when I hit the switch to open the rear cowl flaps I didn't hear the motor running. Sure enough the flaps were not opening. I tried puling and resetting the breaker, and looked for any loose wires on the switch in the panel (the motor was inaccessible due to closed rear cowl flaps making it not possible to get the panels off). After about 20 minutes of messing around with no apparent effect, suddenly it decided to work. I flew it home and exercised the motor once I was back on the ground in Livermore where I am based. It is now running. I did hear a slight hitch in it on one cycle but it seems to be running without issue. My question is for those of you who have had this fail, does it fail hard or is it intermittent? I am wondering if I may have a loose connection somewhere and this is causing the problem and not the motor. There is also a reference to cleaning of the motor assembly in the forum, which I may have my mechanic do if it looks like the motor is the issue. the motor is now about $7800 from Cessna, and about $6K on line from others so i'd like to understand where I may be having an issue and not just swap it out.

[hharney]

B2C2, have the motor cleaned and inspected by someone that understands small low voltage DC motors. Have your A&P install it and make sure it is working properly to make the correct log book entry. Yeah it's not 100% by the book but that's all you can do.

The little motors get moisture in there and the grease dries up. Service will hopefully do the trick

[B2C2]

Hi Herb

okay thanks, I will give that a try. The plane is going in for annual soon so Ill use the opportunity to have this done. I hate these intermittent problems. You are never sure if they are actually fixed.

[Jerry De Santis]

I agree with Herb. They are very simple motors and easy to have cleaned. Also, since your plane is not pressurized, I understand that there is a conversion kit that you can install and eliminate the motor. Maybe someone on this site has more information regarding it.

Cheers
Jerry

[LostKiwi]

http://www.cessnaskymaster.com/mech-...ol-system.html

I don't have that mod installed, so I can't comment on whether its any good or not, but $1495 is a lot cheaper than 7800 bucks for a new motor!

http://www.cessnaskymaster.com/cowl-flap-motors.html

Looks like they do exchange/overhaul of motors too if it comes to that.



Leighton.

[Kim Geyer]

Try Georges Electrical Service in Sacramento CA 916 922-4277. The overhauled 2 for me about a year ago for $700.00 each. It may be more if it has a brake on it.
Talk to Michael Headley
Kim

[Frank Benvin]

Make sure you check your fuses in the engine compartment for your cowl flap motors. Someone put fuses that were over three times the rated fuse size in ours. Check your manual for sizes.

[Skymaster337B]

Check out this older post http://www.337skymaster.com/messages...hp/t-3471.html

RLB accessories rebuilt my motor for hundreds of dollars....not thousands.

He fixed it, returned it with invoice in box, used the trust system for me to pay. Good dude.

[JamesC]

I actually have a spare new one, Part Number C610501-0202 if that works for you. $600 and it's yours. After a cowl flap failure I used to carry it among other things on long trips to the middle of nowhere.
Jim

[jchronic]

B2C2 -
I had the very same problem on my 69 D model a year ago: intermittent operation for a period of time and then stuck closed and wouldn't open at all. Before you dump a bundle on a motor overhaul/replacement, have your mech thoroughly check out the wiring continuity to the motor, especially in the rear engine compartment. There's a lot of heat and shaking back there that eventually causes problems.

We found an intermittent contact that finally gave up the ghost and now the cowl flaps work fine...(until next time anyway...). Also look for any hoses, cables, etc. that may be interfering with the actuator mechanism and putting extra loads on the motor. I have a Wolf oil filter adaptor back there and the feed lines occasionally work there way against the left side cowl actuator rod.

Good luck -

[Don Nieser]

We carry new, repaired and as removed cowl flap motors for all 337 aircraft. Please call Don for pricing. We try to beat any other price. 405-503-4686 or e-mail; nieser.02.337parts@juno.com.

[B2C2]

The plane is in for annual now. After the general inspection we will have a look at the wiring to the motor. I took a look at this once I had it back in the hanger and there is one wire that is loose and has about 1/2inch of clear plastic sleeving that is over the tefzel wire that is missing, and the tefzel wire in that section seems kind of flimsy to me, so perhaps a broken connection internally. this should be easy to see by wiggling the wire while turning on the motor switch. That is a two man job however so I will do this with the mechanic once we are ready to dig into it in a week or so. thanks for all the suggestions on repair of the motor should it come to that. One of the folks is right down the road form me. I also have the STC for cable actuation of the front flaps already, so thankfully only one motor to worry about.

Ben

[B2C2]

Well, extensive wire wiggling failed to produce a hiccup in the motor behavior, so I have asked my mechanic to pull the motor and we will send it to Georges Electrical in Sacramento. He uses them a lot so was comfortable with this path. They are right down the road as well so that's nice. Its still possible its something else but since the plane is out of commission anyway I figured I would do this to rule out a motor problem in the future in case it shows up again.

[B2C2]

So this issue has been resolved. It turns out that there is a connection to the brake on the rear flap motor right where the wires enter the motor case. the wires themselves (Red, Black and White for the brake) are wrapped in a braided shield that is tied to ground. It looks like there was originally some sort of insulation applied to the connection, but this wore off over time, allowing the shield to occasionally contact the exposed terminal and actuating the brake. We found this when after reassembly the mechanism was still intermittent. We pulled the motor out and while we had it connected but not tied to the mechanism we wiggled the lead entering the motor and it made the motor start and stop. Inspection found the exposed terminal issue. We applied some high temp silicone to the exposed connection and put everything back together and it works properly. So if you see this problem, try wiggling the leads where they enter the motor case and see if this causes it to be intermittent. This lead is typically tied to the motor case with a zip tie or clamp for strain relief, so it normally doesn't move much but apparently enough to create the problem.

[hharney]

Thanks for the report and glad to hear you chased down the issue. This is a good thread for those others trying to troubleshoot the CF motors