Temp sending unit?

The temp sending unit is the single wire unit on the driver's side.

I've never seen a wire "on the heater tube", so I cannot comment on that.

The stock lower intake has the temp sending unit by the 5th cylinder. Some intakes also have fittings at the rear of the lower intake by the 8th cylinder.

For testing , use the one by the 5th cyl.

the one on the heater code lines are for the computer and the other is for the gauge.

pretty much what mouse said. The larger connector behind the injector on the #5 runner is the ACT (air charge temperature) sensor.

ACT/IAT = Air Charge Temp sensor/Intake Air Temp sensor (same thing, two different names). This sensor does as the name implies - lets the puter know how dense the incoming air is.

ECT = Engine Coolant Temp sensor. Simply relays coolant/engine temps to the puter.

Both sensors are used for fuel trim, etc.

The Autometer sending unit would indeed take the spot of the OEM one wire temp gauge sender. The OEM sender can be relocated elsewhere to keep the stock gauge active.

rustang87 said:

hmmmmm, I wonder what Jrichker meant by probing both wires of the unit when it is only that single red/white wire...
Thanks for the help guys.

Oh yah, since I bypassed the heater core, can I get rid of the hard coolant lines that the ECT plugs into? Can I move the ECT somewhere else?

Click to expand...

yeah you can remove the hard lines but you will have to put that ECT somewhere not sure but it may beable to on where the other sending unit was. then put your after market gauge where the hard lines where.

not sure maybe you can pm jrichker and get a little more detail as far as that goes. ( he is the man to talk to about wiring).

rustang87 said:

hmmmmm, I wonder what Jrichker meant by probing both wires of the unit when it is only that single red/white wire...
Thanks for the help guys.

Oh yah, since I bypassed the heater core, can I get rid of the hard coolant lines that the ECT plugs into? Can I move the ECT somewhere else?

Click to expand...

I believe that the ECT is a 3/8" NPT thread and the hole in the intake for the coolant hard lines is a 1/2" NPT thread. I picked up a brass bushing from the hardware store and reduced the hole in the intake down to the same threads as the ECT and then put my ECT in. Works like a champ.

rustang87 said:

hmmmmm, I wonder what Jrichker meant by probing both wires of the unit when it is only that single red/white wire...
Thanks for the help guys.

Oh yah, since I bypassed the heater core, can I get rid of the hard coolant lines that the ECT plugs into? Can I move the ECT somewhere else?

Click to expand...

The ECT is located in the heater feed tubing on the passenger side and has two wires.
The wire colors are lt green/yellow and black/white.

The ACT is located in #5 intake runner on the driver's side and has two wires.
The wires are lt green/pink and black/white.

The water temp sender for the dash gauge is located on the driver's side and has a single wire.

Probe the ECT to get the temp readings if you want to check the water temp gauge for accuracy.

Pin 25 ACT signal in. at 50 degrees F it should be 3.5 volts. It is a good number if the ACT is mounted in the inlet airbox. If it is mounted in the lower intake manifold, the voltage readings will be lower because of the heat transfer.

Pin 7 ECT signal in. at 176 degrees F it should be .80 volts

The ACT & ECT have the same thermistor, so the table values are the same.

Here's the table: The values are +/- 15%, so don't get worried if your readings vary a little bit.

Voltages are measured across the two connector pins of the sensor with the sensor connected. Some safety pins used to probe the connector from the rear will be helpful

50 degrees F = 3.52 v
68 degrees F = 3.02 v
86 degrees F = 2.62 v
104 degrees F = 2.16 v
122 degrees F = 1.72 v
140 degrees F = 1.35 v
158 degrees F = 1.04 v
176 degrees F = .80 v
194 degrees F = .61
212 degrees F = .47 v
230 degrees F = .36 v
248 degrees F = .28 v

Ohms measures at the computer with the computer disconnected, or at the sensor with the sensor disconnected.
50 degrees F = 58.75 K ohms
68 degrees F = 37.30 K ohms
86 degrees F = 27.27 K ohms
104 degrees F = 16.15 K ohms
122 degrees F = 10.97 K ohms
140 degrees F = 7.60 K ohms
158 degrees F = 5.37 K ohms
176 degrees F = 3.84 K ohms
194 degrees F = 2.80 K ohms
212 degrees F = 2.07 K ohms
230 degrees F = 1.55 K ohms
248 degrees F = 1.18 k ohms