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Hi all, again on my friend's 71 442, there are aftermarket gauges for oil and temp, so wire were added, and small hose for oil pressure.
I'd like to make the original light work for temp and oil, so I found 2 wires near the wiper motor, a green one and a black with orange stripe. Looking in the wire diagram, the black and orange would be for downshift solenoid (no power and not even a ground).
The green as power with key ON, so could it be for temp switch ?
No. The green wire you found also runs to the transmission and is used for the pressure sensor that operates the Transmission Controlled Spark system. Note that you can run both the mechanical oil pressure gauge and the original OIL idiot light sensor by using a tee fitting at the oil pressure port on the block. You cannot use a tee fitting for the temp sensor, however. The temp sensor needs to be immersed in flowing coolant to get an accurate reading. If you use a tee, the coolant at the sensor stagnates and may or may not represent the temperature in the block. Unless you have a manifold with an unused coolant port in the crossover by the thermostat housing, you're not going to easily run both sensors.
No. The green wire you found also runs to the transmission and is used for the pressure sensor that operates the Transmission Controlled Spark system. Note that you can run both the mechanical oil pressure gauge and the original OIL idiot light sensor by using a tee fitting at the oil pressure port on the block. You cannot use a tee fitting for the temp sensor, however. The temp sensor needs to be immersed in flowing coolant to get an accurate reading. If you use a tee, the coolant at the sensor stagnates and may or may not represent the temperature in the block. Unless you have a manifold with an unused coolant port in the crossover by the thermostat housing, you're not going to easily run both sensors.
Thanks a lot Joe, and why would they unpluged these wires ?
And that sensor would be on which side of the car please ?
And for the temp and oil pressure original wires, should they be coming from the same place of the trans wires ?
No. The green wire you found also runs to the transmission and is used for the pressure sensor that operates the Transmission Controlled Spark system. Note that you can run both the mechanical oil pressure gauge and the original OIL idiot light sensor by using a tee fitting at the oil pressure port on the block. You cannot use a tee fitting for the temp sensor, however. The temp sensor needs to be immersed in flowing coolant to get an accurate reading. If you use a tee, the coolant at the sensor stagnates and may or may not represent the temperature in the block. Unless you have a manifold with an unused coolant port in the crossover by the thermostat housing, you're not going to easily run both sensors.
And where those 2 connection would be located in the car (red circle) ? Trying to find my oil pressure and temp sensor wires.
Thanks
Take another look at the diagram you posted. It's all right there.
Thanks Joe, I have checked the 2 wire I found earlier, the green and orange/black, one as power with key ON and the other one as power with key ON and with the kickdown switch pushed all the way . So that is solved for transmission wires.
But checked all the harness on firewall and didn't find any green and blue/white wire for the oil pressure and temp sensor. Too bad, may be hiding under dash, that's my next search.
Joe what would be the purpose of disconnecting the trans wires ?
What transmission do you have in the car? The black/orange wire is only used for the TH400 kickdown, but was included in the harness in every car, no matter which trans was installed. The green wire is part of the Transmission Controlled Spark system, an early emissions control device. People disconnect it because they think it is hurting the car to have emissions controls.
The firewall connector has two halves, the engine harness and the forward lamp harness. The transmission wires are in the engine harness, the sensor wires are in the forward lamp harness. The wiring diagram shows you exactly where these two wires are located in the firewall connector.
What transmission do you have in the car? The black/orange wire is only used for the TH400 kickdown, but was included in the harness in every car, no matter which trans was installed. The green wire is part of the Transmission Controlled Spark system, an early emissions control device. People disconnect it because they think it is hurting the car to have emissions controls.
The firewall connector has two halves, the engine harness and the forward lamp harness. The transmission wires are in the engine harness, the sensor wires are in the forward lamp harness. The wiring diagram shows you exactly where these two wires are located in the firewall connector.
Thanks again Joe, not sure about the transmission, but it's a 71 442 so I guess it's a TH400. For the forward lamp dash connector I think it's near the brake booster right ? see pic, and the circle is where I found the trans wires.
Yes, that is the main firewall connector. The connector on the engine side of the firewall has two parts, one for the engine harness and one for the lamp harness, which are the two connectors you circled in red in the wiring diagram.
Yes, that is the main firewall connector. The connector on the engine side of the firewall has two parts, one for the engine harness and one for the lamp harness, which are the two connectors you circled in red in the wiring diagram.
Got it, i was replacing the brake booster so I will have a good view and access.
Thank you so much Joe.
No. The green wire you found also runs to the transmission and is used for the pressure sensor that operates the Transmission Controlled Spark system. Note that you can run both the mechanical oil pressure gauge and the original OIL idiot light sensor by using a tee fitting at the oil pressure port on the block. You cannot use a tee fitting for the temp sensor, however. The temp sensor needs to be immersed in flowing coolant to get an accurate reading. If you use a tee, the coolant at the sensor stagnates and may or may not represent the temperature in the block. Unless you have a manifold with an unused coolant port in the crossover by the thermostat housing, you're not going to easily run both sensors.
Hi Joe, would you please clarify why one can have the temp gauge and temp warning light with one coolant temp sensor? When you see use a tee, I am assuming you are talking about splitting the temp sending wire into two directions, one to the stock dash and another path to a new temp gauge - I don't understand how that would interfere with the temp sensor mechanism that is screwed into the block. I know I am misunderstanding your post.
Hi Joe, would you please clarify why one can have the temp gauge and temp warning light with one coolant temp sensor? When you see use a tee, I am assuming you are talking about splitting the temp sending wire into two directions, one to the stock dash and another path to a new temp gauge - I don't understand how that would interfere with the temp sensor mechanism that is screwed into the block. I know I am misunderstanding your post.
The idiot light and the gauge require separate senders. The sender for the idiot light is just an on/off switch that is normally open and closes when the coolant reaches about 250 deg F. The sender for a gauge is a variable resistor that changes the voltage to the gauge as the temperature changes. The tee I'm referring to is a pipe tee. You can use a tee with oil pressure senders because the pressure will be the same in all legs of the tee. You cannot use a tee with temp senders because the temperature will not be the same in the legs of a tee. You want to measure the temperature of flowing coolant, not the temp of a stagnant amount of coolant at the end of a dead end.
