Horn Relay Wiring

[Jonathan_Ferguson]

With the adapting of the Water Sensor, I'll need the Alarm to be off when the Water Sensor says to be on, and I want the Alarm on when the Water Sensor is off. I believe I can accomplish this with a Horn Relay?

Testing with a piece of Wire
Connector's Negative bridged to Negative: Nothing
Connector's Negative bridged to Positive: Sparks
Connector's Positive bridged to Positive: Nothing
Connector's Positive bridged to Negative: Alarm

Horn Relay Terminals - This is what I can't grasp
30: Connected to a powered source when the Ignition is on.
85: Earth
86: Positive of Water Sensor
87:
87a: Positive to Dashboard Light and Alarm
Do I keep the Water Sensor's Negative and the Alarm side's Negative connected together, like stock, or Earth both of them?

 

[KLF]

What is this "Water Sensor" you speak of? Did I miss a post somewhere? Do you have automatic windshield wipers or something?

 

[Jonathan_Ferguson]

What is this "Water Sensor" you speak of? Did I miss a post somewhere? Do you have automatic windshield wipers or something?

https://forum.ih8mud.com/79-95-toyota-truck-tech/227526-fuel-filter.html
https://forum.ih8mud.com/diesel-tech-24-volts-systems/227798-2l-water-sensor.html

 

[Joe Egolf]

water sensor

I presume he is talking about a sedimenter on a diesel?

 

[Jonathan_Ferguson]

I presume he is talking about a sedimenter on a diesel?

In the new setup there wont be a Sedimentor per se.
I'm going to make an adapter on a Lathe so I can use my old Water Sensor in the new Fuel Filter, but it'll be mounted upside down, so I'll need to reverse the electrical signal somehow.

 

[theo]

With the adapting of the Water Sensor, I'll need the Alarm to be off when the Water Sensor says to be on, and I want the Alarm on when the Water Sensor is off. I believe I can accomplish this with a Horn Relay?

You have 2 terminal types on your relay for the load - 87 is Normally Open (NO) and 87a Normally Closed (NC). Sometimes there's a schematic on the relay.

You want fused +12V current to flow into "30" and out "87a" through the alarm to ground. (This is the load.)

You want +12V to flow from the sensor to "86" and out "85" to ground. (This is the trigger.)

Sensor comes on with key and triggers the relay. The load is cutoff since it's connected to 87a. If the sensor fails or shuts off, the relay is no longer activated and current flows from "30" to "87a".

So the alarm doesn't sound with the key off you can use the NO terminal "87" of another relay to supply switched power to the first relay so it only works with the key. You should be able to skip this by using switched power to "30" on the first relay.

Think I got it right!

 

[Jonathan_Ferguson]

All done

Do I keep the Water Sensor's Negative and the Alarm side's Negative connected together, like stock, or Earth both of them?

I now know it's not necessary to run an Earth, just as Negatives.