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Discussion Starter #1
Hello,

I am trying to hook a two speed Taurus Fan up to my eec iv computer. The computer only has one output speed. Basically what I come up with will cut the fan on high at the chosen temp or cut the fan on low if the ac is on. What I need to know is how can I make sure I never have positive current run back to my 5 wire relay?

Obviously besides drawing lines, I know nothing about wiring. Would a diode or resistor guarantee I never get + current back to my 5 wire relay?
 

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If you wire incorrectly nothing will protect the computer.

A relay with a high resistance coil or a transistor buffer would protect the computer.

The EEC4 uses an internal transistor to pull to ground. Ford uses this scheme to control things rather than having the computer output a voltage. The EEC iv transistor is easily damaged by excessive current, so you have to be careful how you wire things to it.
 

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decipha has a write up at his site

on how to wire it for two speeds through ecm control

one is power side and the other is ground side switched
 

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Discussion Starter #4
If you wire incorrectly nothing will protect the computer.

A relay with a high resistance coil or a transistor buffer would protect the computer.

The EEC4 uses an internal transistor to pull to ground. Ford uses this scheme to control things rather than having the computer output a voltage. The EEC iv transistor is easily damaged by excessive current, so you have to be careful how you wire things to it.
Thanks, I got some good parts ordered.

decipha has a write up at his site

on how to wire it for two speeds through ecm control

one is power side and the other is ground side switched
I saw that. My computer doesn't have the hardware for the two speed...And I just can't bring myself to solder a chip to my working unit.
 

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bring yourself to it.
 

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Discussion Starter #6
I can see where it would be more ideal to but, I'm not doing it. If it was colder here, I would look into it. But when the car needs a low speed 10 months out of the year, I'm almost good with going with a one relay set-up where low is the default and high only kicks on when the car can't keep up sitting in traffic with the a/c on.
 

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tell me what you want the fan strategy to do?
 

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Discussion Starter #8
The engine will run too hot during the summer in stop and go traffic with the a/c on. I have to cut the a/c off to cool it back down. The strategy needs a way to switch to high speed so I don't have to do that.
 

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so right now you only use low speed?

my set up consists of a press switch that brings on high for a/c
 

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Discussion Starter #10
yes, just low speed.

In the last year I have put right around 25k miles on my engine. I have had the car run over halfway on the stock gauge twice. Once the other day making wot pulls tuning, then idling with the air on and once in stop and go traffic about a year ago in Birmingham.

It would be nice to have it cut on high for the ac when it needs it in stop and go traffic. The majority of the time though, I'm on the road.
 

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I run mine at 1/2 or just a bit higher

alot more power

If you want to run a press switch for high speed, i can quickly draw up the diagram

you will need a press switch though
 

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Discussion Starter #12
That is a great idea. Do you even have your tweecar hooked up to the fan at all? And what did you do, just unscrew the high side 134a adapter and put a switch there?
 

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I added another fitting to accept the switch

I run relays for the fan, not through the tweecer, but shaker666 here has gone through the tweecer

I will one day out of need I presume.
 

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i know this is a bit old but its relevant so figured I'd post it

a couple years ago I rewrote the fan control in the GUFX strategy (foxbody ecu) so the ecu turns the fan on when the a/c comes on, it saves you from having to wire it up to the pressure switch

its in the latest a9l2 tune and you can apply it to your existing tune by using the patch I have in the tunerpro gufx xdf file
 

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logic to output low speed?

how will high speed be outputted?

the reason for pressure input, is when its cold outside so you can retain, defrost/defog feature.

having the high speed fan come on a/c request is not ideal.
 
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