Electric trim inop

[Rrawlings3452]

My 77 M20J has electric trim control buttons on each yoke (which seems to be rare). However the electric trim will not function from either yoke. There is a left right electric trim toggle switch flipping that does not help. We have reset the breaker and cycled the electric trim on/off toggle switch and still nothing does anyone have any ideas?

[Marauder]

My 77 M20J has electric trim control buttons on each yoke (which seems to be rare). However the electric trim will not function from either yoke. There is a left right electric trim toggle switch flipping that does not help. We have reset the breaker and cycled the electric trim on/off toggle switch and still nothing does anyone have any ideas?

When was the last time you had the trim jack screw cleaned and lubricated? Can you move the trim wheel by hand easily or is difficult to move? If the trim jack screw looks fine, it is either the motor, connection to the jack screw, the power switch is bad or you have a broken wire somewhere. The breaker isn't popping is it?

[Krh3682]

I had kinda the same issue going into my latest annual. The switch would trim up, but not down. Don Maxwell told me that the switch is a fairly common issue with Mooneys. Unfortunately though, they are a few hundred $$ to replace. I know the issue is with the switch because my autopilot trims up and down with no issues..

[Rrawlings3452]

The trim wheel does turn easily and the jack screw seems well lubticated, there is no breaker pop wen using either switch. I am unable to get movement up or down from either switch on both yokes.

[N201MKTurbo]

It is probably the disconnect relay. It is mounted on the firewall just to the right of the vacuum manifold.

 

With the engine off, push the trim button and listen for the relay to click. If the relay clicks then it is not your switch. The fact that you have two switches pretty much eliminates the switches. If a switch went bad the other one would work.

 

Try engaging the trim switch and wiggling the connector to the disconnect relay to see if it starts running.

 

My electric trim has been intermittent ever sense I've had the plane. Iy has always been the relay or the connectors at the relay.

[Marauder]

The cheapest next step is to see if your trim power switch is working. Should be a simple on/off switch. If you can verify power, the problem is downstream somewhere. If the motor is not trying to move, the motor would be the next thing I would look at. The fact that you have two trim switches should eliminate them.

[aaronk25]

Harness under the yoke and sometimes they stretch the wires to tight and the wire makes its way out of the plastic connector. Not sure off applicable to both yokes

[Rrawlings3452]

Thanks everyone this is a great help, if it is the motor where is the motor located??

[Marauder]

Thanks everyone this is a great help, if it is the motor where is the motor located??

Should be in the avionics bay near the jack screw.

[MB65E]

I have had trim inop issues on a Bravo. Turned out to be the AP disconnect switch. I was surprised too... If your trim normally works with only the Avionics master on it might be wired up that way. Not sure how they did it in '77.

Check there first before you replace any parts.

-Matt

[flyboy0681]

 Unfortunately though, they are a few hundred $$ to replace.

 

Few hundred? I had mine replaced a few months ago for over a grand. 

[Rrawlings3452]

It will be a few days before I can get over to the hangar, but I will let you know if any of these options work. I'm also fighting a short or what I think is a shirt in the landing light. When I flip in the landing light switch the entire panel dims and the landing light does not come on has anyone ever experienced this?

[fantom]

Few hundred? I had mine replaced a few months ago for over a grand. 

 

But you share of it was only a couple of hundred bucks

[N201MKTurbo]

It will be a few days before I can get over to the hangar, but I will let you know if any of these options work. I'm also fighting a short or what I think is a shirt in the landing light. When I flip in the landing light switch the entire panel dims and the landing light does not come on has anyone ever experienced this?

I would be more concerned that your circuit breaker didn't blow. It seems that there is a high impedance somewhere in your electrical system. Do you have a volt meter in the plane? Does it drop when you switch on the landing light?

[flyboy0681]

But you share of it was only a couple of hundred bucks

 

All told the invoice was about $1,300. Little more than a couple hundred.

[Rrawlings3452]

I went to check the trim knob and realized it is much stiffer I can not move it with just my fingers (like my Cessna and Cherokee) it takes a whole hand grab and turn. This being my first Mooney I figured that's just the nature of the beast. Let me known if this changes everyone's opinion.

[larryb]

I went to check the trim knob and realized it is much stiffer I can not move it with just my fingers (like my Cessna and Cherokee) it takes a whole hand grab and turn. This being my first Mooney I figured that's just the nature of the beast. Let me known if this changes everyone's opinion.

It should turn easily. I had a stiff trim issue in my 84j and it was a lack of lube on the pillow bearing right below the trim motor. A shot of tri flow and it was fine.

[Rrawlings3452]

I'm still unable to locate the trim motor need further help

[Marauder]

I went to check the trim knob and realized it is much stiffer I can not move it with just my fingers (like my Cessna and Cherokee) it takes a whole hand grab and turn. This being my first Mooney I figured that's just the nature of the beast. Let me known if this changes everyone's opinion.

Well that changes things. First of all, my Mooney's trim wheel is not as easy to move as a Cessna's (you are moving the whole tail on a Mooney and only a trim tab on a Cessna). But you should be able to move it without too much resistance. How long have you owned your Mooney? I re-read your original post and post about the Mooney being new to you. Has the electric trim ever worked? You speak about two electric trim switches on each yoke and also a left and right switch. I'm not meaning to insult you, but you do know that both halves of the switch needs to be moved together to engage the electric trim?

[Rrawlings3452]

Electric trim has never worked since I purchased the plane a few months ago. Each yoke has a up and down single rocker switch. There is a toggle switch that says left and right this changes witch yoke trim switch is active.

[Marauder]

Electric trim has never worked since I purchased the plane a few months ago. Each yoke has a up and down single rocker switch. There is a toggle switch that says left and right this changes witch yoke trim switch is active.

The puzzle is starting to come together. It does not sound like your electric trim switches are the approved ones used. The trim switches I have seen are split switches like the one in this picture: Not saying that a single rocker switch cannot be used, just never been in a plane that has one. Always seen the split switch. Also, there should be a power disconnect for the trim. I don't know all of the approved methods for this but in my plane, I have a separate power switch specific to shutting off the trim. You should have one of these or a separate breaker that allows you to disable the trim in case of a runaway trim situation. What autopilot do you have? Based on what you are saying, you could have a problem in that right/left toggle switch, bad rocker switches, a bad motor and/or no power going to the trim motor. I would be surprised if you don't have a power source for the trim.

[Rrawlings3452]

My switches look different I'll try to get a picture soon to help identify them.

[flyboy0681]

I'm still unable to locate the trim motor need further help

 

Here is a picture from my "avionics bay". The motor is highlighted in yellow and has a chain drive.

[OR75]

the split switch would be an S-Tec

 

It can also be another other auto trim

[N201MKTurbo]

If you want to troubleshoot the motor, there are 4 wires two are the clutch the other two are the motor. The clutch should energize whenever the yoke switch is off center. The motor will change polarity depending on which way you push the switch.