Trim Gauge problems

followme21

Seaman
Joined
May 19, 2008
Messages
65
So my Mercruiser Alpha 1 trim gauge has been pegged to the full up position for some time now.. I have tested the gauge and when I jump from "ground" to the "S" terminal (brown with white tracer) the gauge bounces around and goes full down, I assume that means the gauge is working??? I have power on the "I" terminal on the back of the gauge as well (with switch on). I replaced the sending unit, but before I pulled the outdrive and did it "the right way" I hooked it up and ran the wires on the outside to to make sure it would work correctly, they were long enough and hooked right up.... Anyway nothing changed, gauge still pegged full.. I then grounded the gauge again, this time back on the block as it comes out of the wiring harness and plugged in to the sender. (brown with white tracer). gauge still went to pegged down. I tested the other wire back there and it has no power.. should that be hot? is that the "I" wire? It is black back there on the wiring harness, but purple coming out of the gauge?? any thoughts as to what to look at next? Thanks. (I have also replaced the gauge, with a different one and still same results).
 
Last edited:

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
40,581
Trim system has 12V and ground on the gauge. The sender lead when grounded should peg the gauge full up not down.
 

followme21

Seaman
Joined
May 19, 2008
Messages
65
What are some issues that i can check that would cause two seperate gauges, and a new sender to do the same thing?
 

followme21

Seaman
Joined
May 19, 2008
Messages
65
Oh i did remeber that on my second gauge, when i bench tested it it did go full up. But when i installed it in the boat it reacted the same as the other one. Im thinking somethong in the wiring harness and/or conections, but cant find where the purple power wires goes?
 

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
40,581
but cant find where the purple power wires goes?

It goes on the + side of the gauge

The sender has the Brown/White going to the gauge as you said, and the other lead of the sender goes to ground
 

followme21

Seaman
Joined
May 19, 2008
Messages
65
So i should clarify, back at the motor where the sender plugs into the wiring harness... Ive the got the brown/white sending wire coming from the gauge..where does that other wire (on the boat wiring harness) (black) come from?? And should it have power?
 

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
40,581
where does that other wire (on the boat wiring harness) (black) come from?? And should it have power?

That wire normally is grounded at the trim pump. There is a larger black ground coming from the engine block and goes to the bracket that holds the trim pump. Where that wire connects on the trim pump is also a short black wire with a bullet connector that the sender plugs into.

That said, the other lead from the sender can be grounded anywhere for ground
 
Top