Alpha 1 trim not working up or down

[mwbrown25]

Hello all first post! I have a new to me 1991 Mercruiser 5.0L with a alpha 1 drive. The trim is not working up or down from the commander switches. No clicking. I jumped the trim solenoids at the green and blue wires and the trim goes up and down. The trim limit switch wires are frayed, can I connect these together to bypass? I pulled the switch apart on throttle (commander switch) and am getting about 1 volt at the red wire. I traced that back to a 3 prong connector near the solenoids/pump and am getting 1 volt at what I believe is the red wire there as well. Any ideas on where I should look next? I'm terrible with electrical terms and tests but have a voltmeter and need to learn. thanks

 

[achris]

Bypassing the trim limit can be done, but it plays no role in the DOWN side. If you have no DOWN, the limit switch is not at fault. However, if the wires are damaged and shorting to ground, it could have taken out the 20A fuse. Here is a circuit drawing of the trim system. If you're more comfortable with plumbing, think of wires as water pipes....

Disconnect the limit switch (short the ends together is you want to), and check the 20A fuse, 'a' in the drawing. If it's blown, replace it and try the system again. If you didn't jumper/short the limit switch connections, you'll need to use the TRAILER switch for UP....

The only other thing to check is that all the connections are clean and tight.

Chris........

 

[Bondo]

The trim limit switch wires are frayed, can I connect these together to bypass?

Ayuh,.... Welcome Aboard,..... That's best done inside the boat,.......

Where the wires come in through the transom, 'n meet the wirin' harness, there's little bullet connectors where it's easily by-passed,.....

 

[mwbrown25]

Thank you ALL! problem solved. Where the positive battery cable bolts to the trim solenoids @ 110 amp fuse (D.) on diagram there was some sort of fibrous electrical isolator disk stopping the power going past that point. I removed it and the trim works again. Anybody know why that isolator thing is there? there's one on both sides of that terminal? anyways problem solved for now.

 

[achris]

That would indicate the 110A fuse has 'blown' or failed for some reason. Recommend not using the system without the fuse, it's basically a fire protection system.

Chris....

Here's a picture and some part numbers for you.... #21 is just a fibre washer. It doesn't stop power passing through, it just holds the power lead up off the base of the fuse. The post it bolts to passes the power, not the washer.

 

[mwbrown25]

Great diagrams, thanks for all the help I'm learning alot. I'll double check everything in the morning and re-install this fiber washer. Today I cleaned and tightened all connections. With the fiber washer installed I would get 12.8V at #19 positive batt cable. At the post on the 110A Fuse (#20) right behind the washer I got 3V. I removed the fiber washer and got 12.8V and the trim worked up and down. How would I test the 110A Fuse? would the trim be working if it was blown?

 

[achris]

You just tested it. With it not there, it works, with it in place it doesn't. That's pretty conclusive. Test with multimeter on the resistance scale, but be aware, they can sometimes read 'good' with no current, but fail under full load.

Chris......