Trim Tab Relay


Old 09-01-11, 04:21 PM
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Join Date: Jan 2009
Location: Ottawa Canada
Posts: 72
Trim Tab Relay

I have to install a trim tab pump on a boat the owner gave me two relays
is there anywhere I can buy a 12Volt 30 Amo single relay that would that would work from a single pole double switch

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Old 09-02-11, 06:14 PM
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Join Date: Jan 2009
Location: Ottawa Canada
Posts: 72
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the 2 relays are Sierra part # 876039-9 for Volvo Penta
I have 3 Wires coming from the togle switch and 3 wires coming from the trim pump
There are 5 pins on the relay pin 30 & 87a NC When I connect 12V power to pin 85 & 86the coil energizes and pin 87a & 30 opens
pin 87 & 30 become Closed
Should the Black wire from the pump be connected to the batery the red for the up direction across 87 & 30
And blue wire for the down be connected the same on the 2nd relay

Old 09-03-11, 03:46 AM
Join Date: Apr 2007
Location: Near Buffalo, NY
Posts: 4,239
The pump needs power, and it needs a connection to the negative side of the battery. The black wire provides the connection to negative for both the up and down circuits. It should be connected directly to the battery.

You have two SPDT (single-pole double-throw) relays. Each has a Normally Open (NO) and Normally Closed (NC) output. Pin 30 is common to both outputs. Pin 87 is NO and pin 87a is NC.

The positive side of the battery connects through an inline fuse or circuit breaker to Pin 87 of both relays. The red (up) wire connects to pin 30 of one relay. The blue wire connects to pin 30 of the other. This completes the pump power circuit.

The relay coils need power and negative. They share a negative, so connect pin 86 on both relays together, and connect that to the battery negative.

Connect power (after the fuse or circuit breaker) to the center pole of the switch. This leaves you with two poles on the switch. One connects to pin 85 of one relay; the other to pin 85 of the other relay. None of the switch contacts connect to negative.

Most trim switches are spring-loaded, which means they return to center/off unless they are held in the up or down position. This prevents the system from being energized for long periods if you forget to switch it off.

(Some will say that main power should be connected to pin 30 and the pump to 87, but this is a potential spark hazard. In this case, pin 87a would be energized almost all the time. Not a good idea ...)

Last edited by Rick Johnston; 09-03-11 at 04:08 AM.

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