Gear limit switch locations

[Clparker23]

67’ F: Where are the up/down limit switches located and what is the best place to access for inspection/cleaning. I’m chasing gear not retracting.

 

 

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[Guitarmaster]

10 minutes ago, Clparker23 said:

 

67’ F: Where are the up/down limit switches located and what is the best place to access for inspection/cleaning. I’m chasing gear not retracting.

 

 

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If it's the same as the '75, they are under the belly.  Before you go to the trouble of removing 252 screws, check the squat switch located on the left main.  Mine was out of adjustment by about 1/8" and was giving me fits.  No retract is typically not a limit switch problem.
It's not popping the breaker is it?

[Clparker23]

I think I’ve got pressure sensor instead of squat sensor...I think. Its been acting up, like not retracting on the first throw of the retract switch but would on the second...then it would take 3-4 tries, last time I flew it wouldn’t at all. I havent pulled and reset breaker yet, but it wasn’t popped.


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[Guitarmaster]

I don't know if this is the "correct way" to test, but here goes.  

Take a length of surgical tubing and attach to the pitot tube.

Aircraft on jacks

Gear handle up

SLOWLY roll the tubing like a tube of toothpaste with someone else watching the airspeed.  I can't over-emphasize slowly.

When the indicator reaches the appropriate speed, the gear should come up.  I don't know what the speed is.  Someone on here does.

At least you will know if the A/S switch is working.

One final thought, is it possible you have a loose or partially broken wire in that circuit?  I hate intermittent problems!


 

[Clparker23]

I did the tubing on the pitot trick the other day, just to check if there was leakage in the system somewhere, everything appeared to hold pressure. I think I found the culprit, 25 amp gear breaker is blue colored from corrosion.


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[N201MKTurbo]

Mine did that once. It turned out to be one of the solonoids next to the gear motor.

With mine, if I set the gear handle up and they didn't retract, I could tap the solonoid with a hammer and the gear would come up.

On jacks of course, and if you do this be ready for the gear to come up at any moment.

[Guitarmaster]

45 minutes ago, N201MKTurbo said:

Mine did that once. It turned out to be one of the solonoids next to the gear motor.

With mine, if I set the gear handle up and they didn't retract, I could tap the solonoid with a hammer and the gear would come up.

On jacks of course, and if you do this be ready for the gear to come up at any moment.

Probably could have saved some money on the part and simply carried a hammer with you! 

[Guitarmaster]

50 minutes ago, Clparker23 said:

I did the tubing on the pitot trick the other day, just to check if there was leakage in the system somewhere, everything appeared to hold pressure. I think I found the culprit, 25 amp gear breaker is blue colored from corrosion.


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Pour some Coke on it to get rid of the corrosion. 

[Clparker23]

I’m going to give it a good cleaning and try it out this afternoon. Fingers crossed that what it is.


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[carusoam]

Solenoids are good for a couple of decades... see what the price of a new one is... Lasar.com

Best regards,

-a-

[Jim Peace]

I never have these problems:

 

[N201MKTurbo]

3 hours ago, Guitarmaster said:

Probably could have saved some money on the part and simply carried a hammer with you! 

Have you ever tried taking the belly panels off in flight? It is windy out there and I keep dropping my screwdriver!

[Clparker23]

Negative fix on the breaker terminal corrosion.


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[Yetti]

Three motor leads on a ITT actuator.

We just did the picture thread

[Clparker23]

After thinking about it, I came to the realization that it’s not breaker or throw switch, because it comes down fine...I was told to check pressure switch by jumping two wires and trying it...if it works it’s the pressure switch, if it doesn’t, it’s motor or limiting switch.


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[Clparker23]

Landing gear switch is a three way switch. One side can go bad but that’s not the way you’d bet. Test for continuity across that switch.  Then put the multi-meter across the airspeed safety switch.  “Increase the airspeed” and you should be able to hear that limit switch close about 80 mph and see continuity across the switch at the same time; all without jacking the plane. 

I had to you tube last night how to check ohms on a switch, I’m not 100% sure how though.

On the retract switch, Do I remove the wires connected to the switch? And use ohms?

can it be done with leads connected? Is this all done with master off?




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[Clparker23]

If you're new to circuits, I'd probably watch somebody the first few times to learn.
If you don't have a multi-meter, I'd get one and some alligator clips.  It can be an invaluable, cheap investment. A hobby type is better than one tended for home circuitry for this use IMO. Also get your aircraft's service manual for the circuit diagrams. Invaluable. 
I'm speaking for 69C circuitry but they should be the same. First off, leave the master off or better yet pull the battery terminal. The gear circuit has two circuits; one for "control" or contact, the other "relay" circuit powers the motor. Opening the gear breaker only gets one side; you're still exposed to a potential short.
For testing for a closed switch/circuit (in this case), your testing for a very low resistance. This will work but most multimeters have a continuity setting with an audible alert. This is better for initial troubleshooting IMO. Find the screw terminals on the device and test there. A closed switch will read very low resistance/buzz in continuity check. Test both sides of the gear switch when properly placed. Test the Airspeed Safety Switch (ASSS) as mentioned before. I'd strongly recommend against the motor testing if you're new to this. I also wouldn't jumper/bypass the  ASSS without the aircraft properly jacked. You're asking for potential, expensive trouble.  As mentioned, if you're new to this, I'd probably get with someone who isn't.  Nothing worse than costing yourself money.

I’m showing continuity at the retract switch and the pressure switch at 100mph.


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[Clparker23]

I’ve reviewed the schematic last night quite a bit, I’m down to up limit, I’m going to check the continuity of “common” and “Nc” coming from the pressure switch, it’s a newer switch that’s been replaced I can tell. The down limit is an original.

As far as the relays, if I were to send a pic of what I was staring at, would you be able to guide me to what to check. I’ve seen some relays in pics on here and these look a little different.

The motor/actuater looks newer as well, previous owner said it was rebuilt in CA not long ago.

I’m going to redo my pressure switch, I was by myself the speed was actually around 150, I’m going to try and get it to that 80/90 mark and see if it’s working there.


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[Clparker23]

I found that the 5 amp breaker next to the 50 amp is not showing continuity, it will not pop out or in.


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[Clparker23]

Update:
The 5 amp breaker when checked again checked out good. As well as pressure switch, gear switch and main 25 amp breaker.

I put the plane on jacks, spent a lot of time checking continuity and touching this/that. And never found anything that just jumped out at me. I stepped away for 15-20 min, went back to it, flipped the gear switch and gear goes up. Cycle it again and then it doesn’t. I go back under press on the indicated limit switch in the pic a couple times and re cycle and gear goes up. I sprayed it with contact cleaner while pressing in and out quit a bit, and I’ve been able to cycle the gear regularly now. It seems there’s a delay of 4-5 seconds but it does cycle.

I’m going to order a limit switch and replace, as indicated in the pic, one has been replaced at some point and I think the culprit is the old original. If anyone could advise their thoughts it’s greatly appreciated. (In the pic gear is in the down position).


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[Yetti]

The two relays are for reversing voltage.  I would bet the down relay needs to be upgraded to a newer model.   I hate the metal can solenoids.

[Clparker23]

What relays are available to upgrade to? I located the cutler hammonds online.


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[Clparker23]

I found some used exact replacements at Texas air salvage for $225, is that good/bad?


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[N201MKTurbo]

I would trouble shoot the system before you bought anything.

Why do you think it is the up limit switch?

The big contactors do the heavy lifting. They are the ones most likely to fail over time. Switching large DC currents takes its toll on any contacts.

The double throw contactors are hard to find. I would buy new if possible. they do wear out.

[N201MKTurbo]

http://www.flamecorp.com/Safran-Electrical-Power.php

This distributer carries the contactors.