Gearhead6s

when i installed my FAST EMS i hooked the coolant temp sensor wires to the sensor i in the water pump and i have removed the factory gauge coolant temp sensor. the first time we ran the car with we had the temps for the cold start enrichment and fans set close to factory. well the car overheated when the FAST temp gauge read ~150* and has done it one other time since. when i ride around the temp reads between upper 80's and ~115. i thought that was awful low. we figured that the sensor had a different resistance than what the FAST needed but tech support said it works with all GM sensors and that he had never heard of anything like that. is there that much of a temp difference between the water pump and the head?

DivisnZ28

quick and easy way to check is to just run the vehicle to operating temperature, use a laser thermometer, if you dont have access to one a normal thermo will work, just get a temp off off the upper radiator hose and compare it to the gauge. its not going to be exact since the temp at the sensor is going to be different then in the upper hose but it will give you an idea

Injuneer

Is it possible you have the temp sensor paralled into both the FAST and the stock PCM? That will produce faulty readings.

Gearhead6s

i do have it paralled between the 2 so that my tranny can get signal. is there a way to correct the readings?

Injuneer

You can't hook two devices to a single thermistor type temperature sensor. Having two devices in the circuit with the single circuit effectively alters the resistance that each device sees. Since its the resistance of the sensor that produces thevoltage reading that the ECU converts to temperature, its not indicating the correct temperature.

You need to have a separate sensor for each device. Put the sensor back in the cylinder head and use that for one of the sources.

I run a MoTeC M48Pro, but still have the stock PCM for speedo and IAC control. The water pump sensor feeds the MoTeC. The head sensor feeds the dash gauge, and I put an extra sensor in the line that returns from the back of the heads to supply a signal to the stock PCM.

I put a brass tee in the line... you can see it in this picture. You will also notice the Ram Air box has two IAT sensors in it..... same issue... one for the MoTeC and one for the stock PCM.

http://cjcfo.fbody.com/members/injun...A/DualIATs.jpg

Gearhead6s

ok cool thanks for the help i will get right on that. my buddy with a turbo miata had to do the same thing so that he could run a GM temp sensor for his stand alone. that is on the list of things to do. right after after i find out why my oil is full of sludge and i am blowing oil like crazy out the valve cover and the dipstick tube.