Water Temp guage on 71 LeMans 400?

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Hazel

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I recently purchased a 71 LeMans with a 400. It has nothing but the idiot lights and want to install a water temp and oil pressure gauge. Regarding the water temp gauge, the left-front of the intake has a 3-prong that attaches to the relay for the electric fans. The right front, has a single wire coming from it (idiot light?). Where else can I attach the water temp probe?

Thanks!
 

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You replace the idiot light sender with a gauge sender.
 
I agree no reason to have both. If it were oil pressure I like to T-off ad keep the idiot light just for something to draw attention to the oil pressure gauge, on temp with a cast iron engine knowing exactly when the engine is about to overheat isn't as critical. They will survive even if you don't have any light or gauge and pull over and stop the engine when it boils over.

The same cannot be said about no oil pressure.
 
Nice looking car Hazel! Is that a trunk lip spoiler you can see?
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Remove the wire, turn the key to run, ground the wire, and see if the light comes on.
 
Hazel said:
I recently purchased a 71 LeMans with a 400. It has nothing but the idiot lights and want to install a water temp and oil pressure gauge. Regarding the water temp gauge, the left-front of the intake has a 3-prong that attaches to the relay for the electric fans. The right front, has a single wire coming from it (idiot light?). Where else can I attach the water temp probe?

Thanks!
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Driver side cylinder head water passage between spark plugs 1 & 3. There may be a threaded pipe plug if the idiot light has been moved to the intake instead of the head. I think there is another plug on the passenger side cylinder head between spark plugs 6 & 8, but is a PIA to get to due to the AC evaporator being in the way.
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I have an original 455 HO, the temperature sender came from the factory on the intake. The position in the head is common on Chevrolets.
The sensor with the three wires in the intake was used from the factory for the Transmission Controlled Spark system.
 
Okay, a little more info. The idiot light for water temp is dead. The right front has a wire that runs to my electric fan relay I don't want to remove that one.

The left front has the 3-prong plug and the yellow wire from it also feeds the electric fan relay. You said "The sensor with the three wires in the intake was used from the factory for the Transmission Controlled Spark system." I'm guessing that is needed? Any idea why the yellow wire from that is going to the electric fan relay?

BTW...the idiot light for OIL still works so I'll want to keep that when I install the oil pressure guage. Where's the best place to install the oil pressure line on the 400?
 
Hazel said:
Okay, a little more info. The idiot light for water temp is dead. The right front has a wire that runs to my electric fan relay I don't want to remove that one.

The left front has the 3-prong plug and the yellow wire from it also feeds the electric fan relay. You said "The sensor with the three wires in the intake was used from the factory for the Transmission Controlled Spark system." I'm guessing that is needed? Any idea why the yellow wire from that is going to the electric fan relay?

BTW...the idiot light for OIL still works so I'll want to keep that when I install the oil pressure guage. Where's the best place to install the oil pressure line on the 400?
Click to expand...
The TCS system is for emissions so I would be surprised if all the parts are still there. Where does the hose from the vacuum advance on the distributor go? Anything other than a vacuum solenoid and the TCS no longer is functioning.
You are saying both sensors connect to the fan relay?
You install a T fitting where the oil pressure sensor is and the old and new sensor attach to it.
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As for the oil pressure I just ran a T fitting off the oil filter adapter to keep both the Idiot light and the new oil pressure sender.

I also would use an electric Oil pressure gauge, or at least run a copper line if you use a direct reading gauge. I had the cheap plastic line break on me once, no fun having hot oil spraying all over your interior when you are driving down the road! Not to mention the clean up and Carpet replacement that occured after the line blew!
 
Even better than copper would be a stainless braided hose.
 
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