Gauge wiring with aftermarket ecu ?'s

[Caveman]

I have a FAST XFI ecu that i will be installing once i get back from iraq.. im good with wiring but im not sure about doing some of the gauges such as water temp... the fast ecu has inputs for stuff such as water temp and some others..information thats required for the tune and what not. anyways.. so my question is can i tap that circuit running from the sensor to the ecu for my water temp gauge or will that mess with the ecu or give me bad readings? i looked over all the pinout charts for the ecu and theres no output for signals such as water temp to go out to gauges... any ideas? i emailed fast about 14 times..still no answer from them on that one... thanks for any help!

[98blackbeauty]

why not leave the current ecu and just reprogram it the way you want.
The temp gauge on 94 has 2 sensors 1 for gauge and one for fan operation. Also your tranny if its auto is controled by ecu. as well as other gauges and funtions.

[DETROITMUSCLE]

why not leave the current ecu and just reprogram it the way you want.
The temp gauge on 94 has 2 sensors 1 for gauge and one for fan operation. Also your tranny if its auto is controled by ecu. as well as other gauges and funtions.

Aftermarket ECUs such as the FAST unit allow worlds beyond the stock computer as far as tuning capabilities and information go, they are far superior over the stock units but come at a hefty price.

[Caveman]

Aftermarket ECUs such as the FAST unit allow worlds beyond the stock computer as far as tuning capabilities and information go, they are far superior over the stock units but come at a hefty price.

yes they do...i picked my fast unit up for about $1600. im going to pull the oem gauge cluster out and put in my own..i already have a nice array of autometer gauges. the ecu only needs one water temp..it takes that info and controls the fans on its own. and i have an m6 trans..so no worries about the ecu controlling it. im just wondering if it will mess with the ecu at all if i tap into that circuit with a water temp gauge? agian theyre a little pricey and id really hate to cook it over a $40 gauge lol..

[steddy]

If there's a worry about overheating it, you could always install the jet fan switch kit so that if it went too high for you, or you're in traffic, you could switch it on, but still retain the settings for the fans. Unfortunately, I'm not familiar with the FAST ECU, so I'm not too sure about it, though I think the switch would solve any overheat problems.

[98blackbeauty]

I guess I'm not clear if you are going to run both or just the one. I say this because you mentioned tap into the circuit. Generally the sensors are thermisters or temperature sensitive resisters. most apps. take a voltage from ecu and return it through the sensor to grd. the temp varies the resistance and thus varies the voltage suppied to the ecu and it supplies the current to the temp meter. the gm stock ecu works off a supplied 5v to the sensor, so you'll need to find out if the fast does this also you may be looking at each circuit and measuring it out to be sure. Or at the risk of blowing ecu try it. If you tap into the line you may have to also put diode in line to prevent back circuits to stock ecu if your running both. Like a switching diode 1n1004 would work.

[Caveman]

steddy - im not worried about over heating..im just running the fast unit and that will control the fans by its self, no problems ther but thanks anyways..

plum - the old ecu and every tiny wire unter the hood and most of the chasis its self is going... or thats what im planning on right now at least.. so as far as engine is concerned its just the fast ecu and the few sensors needed to support fuel injection, and then my engine monitoring gauges, temps, press, so on. anways, yes the fast system routs the volts as you described it.. i am just not sure if i should instal that gauge somewhere inline (probably a bad idea). im also thinking maybe just a stand alone water temp sensor just for the gauge? theyre not much $$... again i havnt played around with sensors too much.. but ill look into that diode stuff...