Trying to get trim sender and gauge to work on 1988 Alpha One generation one

Alright, here we go with another problem! About a year ago I purchased the trim sender/trim limit harness from Mercruiser. I have Faria gauges already installed in the boat dashboard. The gauge is brand new and is wired up as follows:
1) Ignition wire is hooked up to (I) terminal just as the other gauges are powered and everything else works correctly.
2) Ground wire is hooked up To (G) terminal just as the rest of the gauges.
3) Attached a wire to the (S) terminal on gauge and ran it to reach stern area where wire ends of sending unit are located.
The needle on the new Faria gauge shows that drive is all the way up without anything being hooked up to sender yet. First blunder is that I did not label which was the sender unit 2 wire bundle and what 2 wire bundle was the trim limit switch. All four wires are the same color (black) so I am clueless as to what is what. I removed the cover on sender and removed the geared switch that has the rotating contacts attached to it. Everything looks brand new inside so there are no issues with deterioration. I then noticed two brass plates or contacts on the back or inner side of sender harness. Question is this: If I were to find out which was which by testing both wire bundles for continuity by putting 12 volt into one wire and hooking the other through a test light to ground should I not be able to get test light to light up? There are resistance issues doing this I am sure but at this point I am clueless! All I am trying to do is this: I do not want to use the trim limit switch and or trailer wiring setup. All I want to do is have the gauge working off the starboard side trim sender unit. Is there a problem doing so? any help would ge greatly appreciated!
thanks again, Tom

Question is this: If I were to find out which was which by testing both wire bundles for continuity by putting 12 volt into one wire and hooking the other through a test light to ground

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Ayuh,... You'll do Better with a Multimeter, rather than a Test light...

1 set of wires will go from closed circuit, to open circuit, as the drive is raised.... That's the limit switch....
The other set of wires will have variable resistence as the drive is raised... That's the gauge sender...

Do not hook 12 volts to any of the wires comming from the two plastic trim sender/trim level switch.

The Trim switch is a nothing more than an on off switch
The trim sender is a variable resistor.

Take your volt meter set it to OHMS and connect the leads to two of the wires. Loosen the two screws that hold the senders caps tight on the outdrive. Now twist one at a time and see if the meter reacts.

You will have to change meter leads to different wires until you get some kind of reaction.

The trim level switch should show ohms and then no ohms.

The trim position sender with show ~ 80 - 280 ohms when rotating.

You should see no reaction if you do not have the right wires connected to the meter.

Thanks Bondo and kghost for the quick reply! I have a multimeter at the shop that has settings for ohms testing. Not much of a meter but I quess it will have to do. Starting to rain here in PA. but maybe I can get boat inside shop and do as you guys instructed. Let me see how I make out with the test and I will post as soon as I get some relevant information for you guys. thanks again, Tom

I purchased the trim sender/trim limit harness from Mercruiser.

Click to expand...

Installed properly it should have sufficed...no additional wires needed if you only replaced the gauge.

"How the trim/tilt works B
"How the trim/tilt works

Before you tear anything apart or replace wiring and switches, test it out; first by visual inspection by pulling back and forth on the wires while operating the switches and then test with a meter. At the commander switches, the red wire will always have 12 volts. The green wire gets 12 volts when the trim toggle is held down. The blue wire gets 12 volts only when the toggle is held up or the trailer switch is pushed in. The purple wire is part of the limit switch circuit.

If the switch voltages are as they are supposed to be then go to the trim/tilt pump assy. and make sure the purple wire connector (single wire) and the blue wire connector with two blue wires on one side of the connection are not corroded or loose. These are the trim position and limit switch wires. Pull them apart and inspect; they should be clean and tight; reconnect them. If necessary, trace the wires to the front of the engine near the slave solenoid. One wire is grounded near there and the other is connected to a terminal. If you don't get a voltage reading at the terminal junction, apply 12 VDC to see if the trim gauge moves. If it does, check for voltage back at the trim pump connections. If no voltage there, apply 12 VDC there to check gauge movement.

Next check the three wire connector (RED, BLUE & GREEN) at the pump assy. This plug can vibrate loose and cause your problem. Pull it off and see if the pins are clean and not corroded; reconnect it.

The RED wire in the plug sends 12 volts from the pump assy. to the toggle up/down and trailer up switches. The BLUE & GREEN wires bring 12 volts from the toggle trim/tilt and trailer switches to the two solenoids on the pump assy.

The GREEN wire goes to the DOWN solenoid while the BLUE wire goes to the UP solenoid.

Did you check the switches with an ohmmeter? The trim/tilt switch is a 2-way switch and will show continuity only when it is toggled in each direction between two of the wires.

Up toggle connects the RED wire to the BLUE wire. Down toggle connects the RED wire to the GREEN wire. The TRAILER UP switch also connects the RED wire to the BLUE wire.

The OD trim limit switch will only send voltage to the trim/tilt switch in the upward toggle position if the OD limit switch is below the adjusted trim limit that keeps the OD being out of the water.

To test the limit switch circuit, lower the OD to the down position and slowly raise it with the trim toggle up until it stops. Then measure the distance between the trim cylinder attaching bolts. If the distance is approx. 22 +/- 1/4 inches, then the trim limit switch is adjusted properly and the commander trim toggle switch is working in the up/down mode.

Go to the trim/tilt pump assy. and make sure the purple wire connector (single wire) and the blue wire connector two blue wires on one side of the connection are not corroded or loose. Pull them apart; they should be clean and tight; reconnect them.
Next check the three (RED, BLUE & GREEN) wire connector at the pump assy. The RED wire in the plug sends 12 volts from the pump assy. to the toggle up/down and trailer up switches. This plug can vibrate loose and cause your problem. Pull it off and see if the pins are clean and not corroded; reconnect it.

The BLUE & GREEN wires bring 12 volts from the switches to the two solenoids on the pump assy. The GREEN wire goes to the DOWN solenoid while the BLUE wire goes to the UP solenoid.

Disconnect the trim/tilt assy. wires from the battery and then check each of the nuts and studs on the solenoids for clean and tight fittings. Each solenoid has three wires and the buss bar connected to it. The bases of them have a black ground wire and a small blue wire to one and a small green wire to the other.

On top of each solenoid, the large BLUE wire from the pump motor attaches to a large copper stud with the solenoid that has the small blue wire at the base while the large GREEN wire from the pump motor attaches to a large copper stud with the solenoid that has the small green wire at the base.

The other copper solenoid studs are connected together with a copper buss bar. One of the two studs will also have a funny looking 110 amp fuse attached to the bar. The large RED wire from the battery connects to the 110 amp fuse. This large red wire is the power for this buss bar. A small RED wire attached to the bar stud sends 12 volts to the switches which in turn sends the 12 volts to the solenoids which turns on the pump motor.

Important: if the studs on the either solenoid are dark and not like a clean penny, especially the BLUE wired solenoid, this solenoid is failing due to age and/or a loose bottom copper stud nut. The dark color comes from heat generated inside of the solenoid by the contactor because it is arcing like welding similar to points wearing out. Change the solenoid.

Cleaning Trim Limit Switch & Trim Position Sender

For the trim/tilt problem you are experiencing, if the wires from the limit switch (port side) and trim position sender (starboard side) are in good condition, they (Switch or sender) can be disassembled to clean out the old hardened grease. SCRIBE the sides of each one and the OD for a reference mark before removal. Clean out the old grease and pump fresh Mercruiser 2-4-C grease thru the zerk fittings before reinstallation. Clean the small brass contact points with solvent and a pencil eraser until shiny; repack w/ 2-4-C grease and reinstall by aligning reference marks."

guyjg,thanks so much for your input with my trim sender unit. Good News! I got the darn thing to work correctly after about an hour and a half hopping in and out of the boat. My first mistake was "not marking and identifying trim limit and trim sender harness's. Second was trying to power harness with 12 volts through trim sender (I thought I might of cooked something!). Anyway, I guess I got lucky in that respect! lol. This is what I did: *LOWERED TRAILER JACK ALL THE WAY DOWN SO AS NOT TO HIT GROUND WITH SKEG IN FULL DOWN POSITION*
1)cut off and stripped all four wires (2-two pair bundles). Next I stripped wire from (S) terminal on gauge. I then took a piece of 12 gauge wire and a 20 amp inline fuse and bolted one end to grounding block on engine. I trimmed drive fully down because before correct hookup gauge was reading full up position. Held stern or transom end of (S) wire and ground simultaneously testing for reaction on gauge with each 2 wire bundle. Luckly, I got power to gauge on first test and gauge reacted but was way off from showing full down so I simply loosened the two adjuster screws on starboard side which is the trim sender. Adjusted about 4 or 5 times to get the gauge to read that drive was in the full down position. Raised drive all the way up and feathered out adjuster until I got it to read pretty accurately. Used heat shrink connectors on all wiring connections. And thank God it works! I thought originally that I either shorted out or damaged the sender, or the new Faria gauge was either faulty or incompatible with sender. ( I found out from a guy in Australia on Breezeworks that he did the same thing as I did and had no problems with compatibility and he was correct. It works accurately!
kghost, I tried to do an ohms test the way you wanted me to do but the multimeter I was using was a pure heap of garbage! lol That would have helped me out a bit if I had taken that course of action originally! That brings me to another question: What multimeter do you guys generally use?
I'm not talking about Snap-On which by the way are a great line of tools, but something reliable for under say $100.00? Is that possible? Maybe I am asking for too much but figured I would ask anyways! lol Just tired of working like a caveman with stone tools thats all!lol
I finally got controller wiring hooked up also and both the neutral safety switch and the man-overboard switch are working correctly. That was tons of fun also!lol Some genius was goofing around with the man overboard switch and somehow inverted the switch in the connector so I like another genius, I mounted controller and clicked in the throttle only button (Quicksilver Classic 3000). I think someone was looking out for me up above because I was somehow able to pry it back out without breaking the darn thing. I then inverted the switch in the harness plug 180 degrees and was able to get the man-overboard switch and lanyard to operate properly. When I first wired it I was not getting any power to coil and thought I had done something wrong with wires. As soon as I pulled switch down it fired right up but it would not hold lanyard clip in correctly in that orientation. Oh boy, what a proper pain in the you know what! lol Well, I am not the sharpest pencil in the box but was still able to make everything work with the help from you guys! Thanks a million, Tom

http://www.sears.com/shc/s/p_10153_12605_03482175000P?prdNo=5&blockNo=5&blockType=G5

This meter is at sears and it has a tempurature probe in 'F that can come in handy.

$59.00................1/2 of what you were looking for.

Great kghost, thanks for the lead! I roughed it out this time but next time it will be different! lol. That way I don't have to drive you guys banannas! All this stuff is first time around and I just don't want to make any assumptions which we all know can lead to expensive mistakes. Couldn't have done it without you guys!
sincerely, Tom

Thanks a million gl115 for the manual. Would you believe that I had the entire manuals for my particular application and my laptop crashed and I lost everything about a year ago.
That is a great help to me! I thank you kindly sir! Anyways, I am late in the game for putting boat in the water but all the same I need to water test this old girl once and for all.
I planned on launching at a local public boat ramp on Sunday if I can get the rest of my safety gear together by then. I will let you guys know how it goes on Sunday night! Wish me luck, Tom