Tilt trim motor problem

[Rstacy]

My boat is 1979 Baja with a Merc 90 on it. Last year the tilt/trim motor started stalling. I would tear it down, find nothing and it would run again for a bit. Both up and down solenoids are good and full voltage is getting to the motor. It got so bad that I drilled a small hole in the end bell so that when it stalled out on the water I could stick a piece of music wire in the hole and move the armature. This would get it running again.
I finally purchased a NOS (new old stock) motor reservoir pump and all was good for a couple of months but now the new pump is doing the same thing. The solenoids click, the motor is getting the full 12 volts but the motor doesn't turn. With this pump if I let it sit for a day it will start running again.
Before I buy a new pump for $400 am I missing anything here? Are there any better pumps that will accept the 4 lines for my two tilt cylinders?

 

[Chris1956]

It sounds like the old motor had an open winding. If the PTT motor happened to stop on that winding, the motor will not run.

Your brushes are good?

 

[tommarvin]

Dude your smarter than i am about T&T
Is the new old stock motor reservoir pump the whole T&T unit unit this always fixs the problem, or is this just part of the whole T&T unit? you need the whole unit.
Why would it work if you let it sit for a day?
There has to be air in the lines, Oh open the fill cap where the ATF goes inmake sure it full of atf and run the motor up and down 10 times to bleed the air out of the system done.

 

[jimmbo]

ATF? In the old remote Power Trim system(2 rams outside the Transom Bracket), Merc specified 20W -20 oil as the fluid. They didn't spec ATF until 84 when they introduced the integral Power Trim.

 

[Rstacy]

I agree that the original motor acted like an open winding. So does the new old stock motor. That's the strange part.
The replacement motor has been up and down dozens of times before it started acting up. The fluid level is full.

The new motor came with everything except the valve body. There was a label with the replacement motor specifying 30 weight oil.

I am hoping that I am missing something here but if I have to spend $400 for a new motor, is there a newer design that will accept the 4 lines from my 2 rams?

 

[Chris1956]

Gee, I would hope it is some sort of bad electrical connection. A NOS part should last many years.

For test purposes, you can connect the PTT motor directly to the switch, bypassing the solenoid.

The original PTT switches were replaceable as well. They were copper disks that made contact.

 

[Rstacy]

I have done some pretty extensive testing to confirm that it is not electrical. The solenoids are clicking and I do have voltage on both sides when closed but I think that I going to jump one just for the heck of it. It wont take long and will verify for certain that there is a motor issue.
Does anything go wrong in the valve body that will lock up the pump?

 

[Chris1956]

You do have a good ground onto the motor body, right? I think they are 6AWG or close to that,

I have never had the pump lock up on me, but I guess it could happen. The test is to remove the upper reservoir and motor and see if she runs properly.

 

[Rstacy]

Funny you mention that. I ran a second ground wire just to be sure. I checked it yesterday and the motor was still not running.
I am going to jump a solenoid and then probably drill another hole in the end cap so I can push the armature with a wire to get it going. The season is winding down here so I have all winter to think about it.

 

[Chris1956]

Clearly if you can push the motor to make it spin, the pump is OK.

Those PTT motors had a bi-metal circuit breaker which could get hot an open if the motor overloaded. I had a piece of dirt get between the points and the motor wouldn't run. Maybe you have a partially open breaker? Just a guess.

 

[sam am I]

Yes, jump the whole PTT relay/solenoid setup with a pair of pliers or what have you's just to be sure.............If no movement or hum or any other indication that the motor is using current, it has to be an flaking out open somewhere in the wires leading from the PTT relays /solenoids to the armature.....Spade lugs, crimp connectors, brush/commutator connection, etc, etc. Sounded to me like the brush/commutator area is flaky.

 

[Rstacy]

I got back to it today. Its been sitting for a week and still no go. This is a good thing. I jumped the solenoid with a pair of channel locks and absolutely nothing. No motor, no spark, no current draw. I give the motor a little tap on the end and away it goes. Multiple cycles and all is good.
It certainly looks like my recently purchased NOS motor has the same problem as my original motor.

 

[sam am I]

It certainly looks like my recently purchased NOS motor has the same problem as my original motor.

It's certainly possible but, I'd lean more towards something that didn't change, as in wiring/connectivity etc.

That said,

If you're running solenoids (not relays), then I'll assume you have a three wire PTT motor.

How those (soleniod setup) works, in a nuts shell, is the motor's third wire (blk) remains grounded and each solenoid (one for up, one for down) in turn is used to send 12V to either the green or white wires.

If you can short across either solenoid and this produces NO hum, buzz or motor movement what so ever, check that third wire (blk) and make sure its grounded and in good shape.