LED indicator help

[Chalupa102]

The other day i installed an LED to tell me when the radiator fan comes on. My coolant temp got to about 205° F and the light never lit up. I believe the fan comes on somewhere between 195-200°.

At first, i had the positive wire of the LED going to the wire right after the fan. The negative wire is connected to a ground point on the front left suspension tower. After that didn't work, i connected the pos wire to the wire before the fan and left the neg wire where it was, and still nothing.

I know the LED works because i connected the positive wire to the pos terminal on the battery yesterday and it lit right up.

Where should i wire it up so the LED will let me know the fan is running?

This is the best i could do, copied from the manual for your reference:



This is copied directly from the manual to give u an idea about it. Unfortunately i didn't put in the #s for the terminals though:

The current is applied at all times through the RDI FAN fuse to TERMINAL 5 of the FAN NO.1 relay. When the ignition SW is turned on, the current flows through the ECU–IG fuse to FAN NO.1 relay (Coil side) to TERMINAL 6 of the engine control module. At the same time as this current flow, the current from ECU–IG fuse flows to the FAN NO.2 relay (Coil side) to TERMINAL 3 of the pressure SW.

1. Low Speed Operation
When the A/C system is operating, the FAN NO.1 Relay is turned on. As a result, the current flows from the RDI FAN fuse to FAN NO.1 relay (Point side) to TERMINAL 2 of the radiator fan motor to TERMINAL 1 to TERMINAL 3 of the FAN NO.2 relay to TERMINAL 4 to TERMINAL 2 of the radiator fan resistor to TERMINAL 1 to GROUND, and the radiator fan motor rotates at low speed.

2. High Speed Operation
When the pressure SW is on or engine control module operated, the FAN NO.1 and NO.2 relay is turned on. As a result, the current flows from the RDI FAN fuse to FAN NO.1 relay (Point side) to radiator fan motor to TERMINAL 3 of the FAN NO.2 Relay to TERMINAL 5 to GROUND, and the radiator fan motor rotates at high speed.

[atfab]

Assuming all the wiring is connected correctly. put the LED across the fan.

[JeepNmpg2]

Originally Posted by atfab

Assuming all the wiring is connected correctly. put the LED across the fan.

Agreed

[Chalupa102]

Originally Posted by atfab

Assuming all the wiring is connected correctly. put the LED across the fan.

I'll do that tonight.

[Piwoslaw]

I'm working on the same thing, just half a step behind you. (It'd be done if I had more time this week). The wiring is in place, just a few details left. I hooked the (+) of the diode to the (+) of the fan, (-) to mass. I also checked to make sure that touching the (+) wire to the (+) of the battery turns the fan on.

Good luck, Chalupa102, I'll be waiting to see how it goes. I'll post if I get it done first.

[brucepick]

Hopefully you guys will have it all hooked up soon.

For what it's worth, my fan comes on around 204-206 degrees F ('97 Civic).
205ºF might not be enough to make it come on.
Of course you could check by taking a look at the fan - assuming you can stop the car and get out without the coolant temp changing a whole lot.

[Chalupa102]

Originally Posted by Piwoslaw

I'm working on the same thing, just half a step behind you. (It'd be done if I had more time this week). The wiring is in place, just a few details left. I hooked the (+) of the diode to the (+) of the fan, (-) to mass. I also checked to make sure that touching the (+) wire to the (+) of the battery turns the fan on.

Good luck, Chalupa102, I'll be waiting to see how it goes. I'll post if I get it done first.

Sounds good. Let me know what happens and good luck to u as well bro.

I didn't even think of touching the (+) wire to the battery. If what i just did doesn't work i'll have to try that out.

[atfab]

I'm Sorry, I hope you are using a 12 Volt LED.

[Chalupa102]

Finally got the led to work . When i was coming up the hill just now to get to my road it came on at 204° and when off at 202°. Thanks everyone for ur help with this.

[Piwoslaw]

I got mine hooked up and took a ride. Unfortunately, the LED is always on
My theory is as follows:
My fan has two speeds: the fast is with "straight" +12V (or 13.8, or whatever) ie no resistors in the way, the slow is when there are resistors lowering the current. I believe that there is always 12V on the line when the engine is on, but resistors keep the current down low enough to keep the fan from starting when it's not needed. This current is enough to light the LED, though. Any ideas what can be done with that? Maybe more resistors in front of the LED? Just guessing.