Transom mounted trim pump motor wiring issue

[MPrimeaux]

Ok everyone, I'm a little stumped and was hoping someone could point me in the right direction. I have a 1978 Mercury 500 with the old transom mounted, external power trim pump. Uses 2 cylinders, 4 hoses, has the rectangle reservoir, One solenoid, and two button trim switches. I bought a replacement pump motor and reservoir because mine was starting to drag pretty bad. A tap or two from a hammer would get it going again for a few seconds... but it needed to be replaced. The original pump motor had 2 wires (green and blue. had an additional black wire going from motor case to the "I" terminal on the solenoid) and the new one has 3... Black, Green, and Blue. I wired it up with the black wire landed on the "I" terminal, the green on the terminal with the green wire from the "down" trim button and the blue on the main terminal of the solenoid. Had to run an external ground to the frame of the solenoid to ground the coil due to the replacement reservoir being plastic. Works fine with the down button, but with the UP button the motor does run and runs in the opposite direction, but the solenoid latches and won't release until I pull the + or - off of the battery. If i just jump power from the battery straight to the solenoid coil it works energizes and de-energizes correctly. It only latches when you use the up trim button. What in the world is causing this?? Any ideas?

 

[The Force power]

I never had one of those but others where like this;
Blue is up
Green is down
Black is common Ground

 

[achris]

The solenoid should only have 4 terminals. 2 large which have the red (from the battery) and the blue (to the pump motor). The 2 small terminals should be just straight plus (small blue) and minus (black). If you have one with an ' I ', then you have the wrong solenoid, but we can still work with that.

Take everything off the ' I ' terminal, leave it blank. The other terminal will have an ' S ' on it. The small blue wire goes on that terminal. The heavy black from the battery and the black from the motor need to be connected with a nut and bolt to the case of the solenoid (or use the mounting bolt for the solenoid)...

Chris........

 

[MPrimeaux]

Thanks guys for the help. I do have an update. After several hours of staring at this trim pump, re-wiring, and researching if there was any difference in this motor and the OEM (other than the physical number of wires), I was hungry and my beautiful bride got home from work and decided to walk away and look at it again today. After supper and a couple of episodes of The Voice, we were turning in and I was laying in bed thinking about this problem and just started thinking about it as an electrician and not a "boat mechanic".... which I am most definitely NOT..... and it came to me. Me being me, taking that solenoid off of the old pump housing and re-installing it on the new was NOT good enough and I decided to take all of the wires off, clean all of the terminals, apply some electrical grease, and re- terminate. I noticed that the "S" terminal was just a touch loose and tightened it ever so slightly. That solenoid was latching..... the ONLY way that could happen is if the "S" terminal was shorted to the main contact somehow. Solenoid energized, main contact closes allowing 12v to go through to the load side (big blue) and THAT was also keeping the solenoid energized. At 12:45 a.m. I couldn't stand it... Got up and threw my pajama pants, went out and checked continuity from the main contacts to the "S" stud.... nothing.... OL. Thinking about the mechanics of a solenoid works... I knew it HAD to be touching inside somehow. Went ahead and loosened the "S" terminal and rotated it CCW just a smidge and tightened it back down. Presto.... working as intended. Must have rotated the inside of the S terminal just enough that the armature would touch it on the inside when energized and thus..... latching it in like a Start/Stop.... with no stop button!

 

[MPrimeaux]

The solenoid should only have 4 terminals. 2 large which have the red (from the battery) and the blue (to the pump motor). The 2 small terminals should be just straight plus (small blue) and minus (black). If you have one with an ' I ', then you have the wrong solenoid, but we can still work with that.

Take everything off the ' I ' terminal, leave it blank. The other terminal will have an ' S ' on it. The small blue wire goes on that terminal. The heavy black from the battery and the black from the motor need to be connected with a nut and bolt to the case of the solenoid (or use the mounting bolt for the solenoid)...

Chris........

This is the diagram I looked all over for!!! Where did you find it if you don't mind me asking? I can't seem to find much info on the trim pump parts. I'm guessing because it was an accessory. Thanks a bunch for this and all of the help! I found the diagram for Type A with 2 solenoids, but couldn't find this one.

 

[MPrimeaux]

Think I got all of the good out of this one.... Anyone have any experience taking this to a starter/alternator shop and having them rebuilt?

 

[achris]

This is the diagram I looked all over for!!! Where did you find it if you don't mind me asking? I can't seem to find much info on the trim pump parts. I'm guessing because it was an accessory. Thanks a bunch for this and all of the help! I found the diagram for Type A with 2 solenoids, but couldn't find this one.

I used to own a Merc dealer/service centre. I still have all my manuals.

 

[MPrimeaux]

I used to own a Merc dealer/service centre. I still have all my manuals.

Well that helps!! Man thanks for all of the help, I really appreciate it. Now to go put all of this junk back together!