CTS question, 3 wire?

[SHOoff]

Ok, so I have this problem when running the MS-II on my car.

I'd like to have my coolant gauge operational. All I have is the stock 3400's 2-wire sensor. The 3rd gen reads the sensor and sends that info in a data stream to the cluster which moves the temp needle appropriately. If I hook both the MS-II and the stock PCM to the yellow wire, then only the gauge will show appropriate temp, but the MS-II registers about 96* when fully warmed up. And this, of course, leaves it in warmup mode and eventually brings the idle up to around 2800rpm, and keeps it out of closed loop. So, for the appropriate running of the engine, the gauge was sacraficed today.

Would a 3 wire CTS solve this problem for me, or would it be best for me to add a second CTS for the stock PCM to use?

[Mr.H.O]

A three wire sensor should allow you to hook up the green? wire to your MS-II leaving the yellow wire hooked up to the PCM seperately. Im unsure however of how the resistance versus temp characteristics are on this sensor. Theoretically both the gauge and pcm sections of the sensor should share the same resistance versus temp values. If thuis is the case than you'll be good.

[Juglenaut]

Does the MS-II have a Voltage reference coming from the wire that is spliced into the stock temp wire?

If the MS-II temp wire puts out a voltage for referencing a 2 wire sensor (ground and signal) and can not be changed to remove the pull-up voltage then you will have to use a second sensor. If the MS-II sensor wire has no voltage out to the sensor and the OEM/AFM gauge uses a 3-wire sensor the MS-II should work.

A 3-wire sensor is basically the same; power, ground, signal where power is not a reference and the input to a device where the input sends no reference out. In other words on a 3-wire sensor when the signal wire is cut the gauge side is cold and the sensor side has some voltage in the linear path where a 2-wire sensor the gauge side sends out 5 volts.

[95 V6 J body]

Juglenaut, I see you work for DD. I have a VFD3-ORIG6 setup that I'm wiring into my vehicle, and I'm wondering if you can use the 3 wire CTS, or if you must use the one supplied with the cluster?

[Superdave]

Does the MS-II have a Voltage reference coming from the wire that is spliced into the stock temp wire?

If the MS-II temp wire puts out a voltage for referencing a 2 wire sensor (ground and signal) and can not be changed to remove the pull-up voltage then you will have to use a second sensor. If the MS-II sensor wire has no voltage out to the sensor and the OEM/AFM gauge uses a 3-wire sensor the MS-II should work.

A 3-wire sensor is basically the same; power, ground, signal where power is not a reference and the input to a device where the input sends no reference out. In other words on a 3-wire sensor when the signal wire is cut the gauge side is cold and the sensor side has some voltage in the linear path where a 2-wire sensor the gauge side sends out 5 volts.

Not sure what 3 wire you are looking at but that's not how the normal GM ones work...


It's basically 2 CTS's in one. Ground referance and 2 isolated outputs.

[3400-95-Modified]

Not sure what 3 wire you are looking at but that's not how the normal GM ones work...


It's basically 2 CTS's in one. Ground referance and 2 isolated outputs.

Yup... one to feed the gauge and one to feed the ECM.

At least thats how my Beretta is setup. 95 used to be one single wire sensor in the head for the gauge, and then one 2 pin sensor in the Lower Intake for the fan switch, ECM reading. But Now I'm 96 wiring, so I have one 3 pin sensor in my motor.