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80-120-Amp Relay System, TJ’s Only Taurus & Flex-A-Lite II Electric Fans

#1 User is offline   Daless2 

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Posted 10 July 2003 - 11:48 PM

Create an 80 to 120-Amp Relay System (TJ’s Only, Not for YJ’s or Rubicon’s on JU Forum

Disclaimer for JU Forums Only:

I have no clue if the Laws of Electrons and Current Flow apply equally to Jeep YJ’s and Rubicon’s as they do on the Jeep TJ’s.
I am confidant and will stand behind this design for TJ’s requiring the ability to switch a high current draw device, such as the Ford Taurus Electric Cooling Fan.

I DO NOT know or have any experience in knowing if it will work on a YJ or a Rubicon. If you need an answer to this I would suggest you check the other forums. Perhaps there is a post and discussion already going on. Else I am sure you could start a new thread there.

Anyone know for sure??????




That said, here it is.

A few days ago someone put a post up (was it for a TJ or a YJ I don’t really remember) asking for a source for a High Current Relay required when installing a Ford Taurus Fan installed in a Jeep.

If that request was for a TJ, then I have a rather cost effective solution for you.


Take Three Standard 40 Amp Bosch Type Automotive Relays and wire them together in a parallel circuit.

By doing this, the current flow through all three relays is reduced to approximately one third of the total current flow through the circuit.

How much do these relays cost? About $0.89 each!

Here’s the circuit. It’s pretty self-explanatory.

Posted Image



Wiring it up

A big fat wire (battery cable type) comes from the battery and goes to a junction point, where it splits off into three 10-gauge leads, which go to Pin 30 on each relay. (Please keep these 10 gauge wires shorter then 5 feet in length. This shouldn’t be a problem for you. Just group the three relays together back to back to back.)

Three additional 10 gauge wires (again less then 5-feet long) connect up to each relay via Pin 87 and connect up at a junction to another big fat battery type cable, which will go to the Taurus Fan.

When the three relays are activated simultaneously current will flow through each relay via Pins 30 to Pins 87.

To activate the three relays build a small, parallel wiring harness that goes from your in-cab switch or the fan thermostat to relay coil Pin 85. Then connect Pin 86 on each relay to Ground.

When the switch or thermostat sends +12 volts to the relay via Pin 85 all three relay will simultaneous activate the relay coils.

You can use 18-gauge, even 22 gauge wire for the relay coils connections as this is a very low current (amp) draw.

I have tested this relay circuit in my shop on a TJ. It works great. Things started coming apart when I forced 159 amps continuous draw.

As stated before, the Ford Taurus Fan requires the ability to handle 80 amps of current draw at start-up. Given each of these relays will handle 40 amps this circuit can easily handle the draw. In fact, any two of these three relays can and does handle it.

I tested just two 40-amp relays wired in Parallel. The system burns up at 103 amps. Way more then you need however I would encourage you to use the three relays wired parallel to have excesses current flow capacity

The 40 Amp Bosch Relay I am using is part number 0-332-209-138-AS40150. Purchased at AutoZone.

I hope some of you may find this useful.

Have a great night folks.

Frank

#2 User is offline   Jim B 

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  Posted 11 July 2003 - 09:11 AM

Frank,

Good info. I was not aware that people were using a Ford Taurus Fan to cool down a TJ. What is wrong with the stock setup?
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#3 User is offline   Daless2 

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Posted 14 July 2003 - 03:23 PM

Hi Jim,

Sorry for the delay in replying.

More then a few folks have replaced their stock clutch fans with aftermarket fans. I have replaced mine with a Flex-a-lite and have done a lot of temp testing with it. Hands down it outperforms the stock setup in my TJ.


If anyone has an interest in reading my testing results they can be found on the JU forum at this address.

http://jeepsunlimited.com/forums/showthrea...9&highlight=Fan

I won my flex-a-lite in a raffle, but the thing is pricey. About $200.

The granddaddy of all electric fans is the one that comes in the Ford Taurus with 3.8 L engine. This thing moves some serious air. The drawback to this fan is that it's current draw is right up there with a starter motor at start up. This requires a special solenoid available from Ford for about $68. Rather then buy that solenoid a friend asked me about a year ago to see if I could come up with a more cost effective solution, thus the parallel relays.

Just put it up for some folks who might need it some day.

Have a great evening, I am!

Frank

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