94-95 Mustang 5.0 AODE MS3 Gold Box w/ Microsquirt

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beyondEOD

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Nov 23, 2019
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Next question on the 86-93 Harness EFISource has the following configuration:
Pin 57(Ing 12V) jumped by a 330ohm resistor Pin 36(Spout)
Pin 36 wired to MS3 Gray 26(Tach)

When comparing the 93 EEC vs the 94 EEC pins 57 and 36 have the same purpose on the harness.

@a91what What is the purpose of the resistor as compared to just jumping with a wire? (Is this lowering the circuit voltage into the MS3 to 5v?
 
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beyondEOD

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Nov 23, 2019
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AC cycle switch on pin 10 is a 12v+ input signal. I used the nitrous input for this. The wot relay needs a ground trigger, an unused inj output will do just fine. You will want to find the relay and swap pin 87a to 87. This way the MS3 can turn the compressor on instead of off, this is how i did mine.

I like to take the grounds to a common wire that travels back to the battery for the lowest ground offset value.

Found an issue here this relay is part of the 94-95 CCRM and is located on a PCB. How can I make this work?
 

beyondEOD

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Sounds good. Still installing a relay in-between the MS3 and the ACCS Relay in the CCRM as well?

EECGray MS3Black MS3
WOT A/C Cut​
54​
-​
27​
-​
A/C CS​
10​
8​
-​
-​
Pin/Relay: EEC-10/86, Gnd/30, Gnd/85, MS3-G8/87​
 

beyondEOD

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Nov 23, 2019
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Okay I'm about to order the parts I'm missing to do these two relays.

Can someone basically triple check I have this diagram setup correctly to run the wideband only when the FP relay is triggered, then the ACCS relay triggers gorund to Flex In when 12v comes in on the stock harness pin 10 from the ccrm. Wideband_ACCS_Relays.PNG
 

Blown88GT

Founding Member
Nov 13, 1999
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You don't need the diodes across the small relays because their coils are so small.
Instead of the fuel pump relay, you can use the EEC Power Relay, then you would only need one additional relay which can be a simple automotive 30 or 40 amp relay available everywhere, no need to order it.
2018-03-10_080526.jpg
 

beyondEOD

Active Member
Nov 23, 2019
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So you suggest that I use the power out from the EEC relay(MS3 power source) to also power the o2 sensor? In essence eliminating the relay on the left of my diagram?

I still need the relay on the right for A/C Control.
 

a91what

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No, the wideband should not be powered when the engine is not running. Unless you want to shorten the life of the sensor.
Do NOT wire it to come on with the ECU, if you need to have it wired to key power for testing install an empty fuse socket that can be used to jumper power to it.

Otherwise the diagram looks fine.
 
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Blown88GT

Founding Member
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I added a toggle switch from 85 to ground.
I keep forgetting this is a Microsquirt on a '95. You need both relays. You don't need the diodes. My MS has a 2N2222 driving the relay coil of the WOT relay. A 2N2222 will sink 1A, relay coil draws 1/3A.
 
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