73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Interior & Equipment => Instrumentation => Topic started by: teamcurtis on January 25, 2017, 11:50:42 AM
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1978 c10 350
So my temp gauge has never worked since buying this truck. The gauge always reads full hot, even when the key is in full off position.
Its my understanding that a grounded wire would make it read hot, but with the key off this shouldnt be the problem right?
Side question, where is the sending unit? I see a sensor towards the back of the passenger side of the engine. Is this the oil or the temp sending unit? Its not hooked up either.
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The gauge won't read with the ignition off. The sending unit should be at the front drivers head. The one in the back should be the oil sending unit.
Chris Lucas
73-87chevytrucks.com
squarebody.biz
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1978 c10 350
So my temp gauge has never worked since buying this truck. The gauge always reads full hot, even when the key is in full off position.
Its my understanding that a grounded wire would make it read hot, but with the key off this shouldnt be the problem right?
Side question, where is the sending unit? I see a sensor towards the back of the passenger side of the engine. Is this the oil or the temp sending unit? Its not hooked up either.
I have a similar issue to this, mine is always stuck in the middle regardless of hot or cold.
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1978 c10 350
So my temp gauge has never worked since buying this truck. The gauge always reads full hot, even when the key is in full off position.
Its my understanding that a grounded wire would make it read hot, but with the key off this shouldnt be the problem right?
Side question, where is the sending unit? I see a sensor towards the back of the passenger side of the engine. Is this the oil or the temp sending unit? Its not hooked up either.
The temperature gauge registering full hot implies the gauge isn't connected to its sender. The gauge needle may "rest" in the full hot position even with the ignition off since there is no spring to return the needle to cold when not powered.
Exactly where is the sensor you found towards the rear passenger side of the engine... on the exhaust side of the cylinder head?? As Captkaos stated, the factory location for the engine temp sensor is in the side of the cylinder head between #1 and #3 cylinder exhaust ports.
I have a similar issue to this, mine is always stuck in the middle regardless of hot or cold.
Check power and ground to the gauge.
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1978 c10 350
So my temp gauge has never worked since buying this truck. The gauge always reads full hot, even when the key is in full off position.
Its my understanding that a grounded wire would make it read hot, but with the key off this shouldnt be the problem right?
Side question, where is the sending unit? I see a sensor towards the back of the passenger side of the engine. Is this the oil or the temp sending unit? Its not hooked up either.
The temperature gauge registering full hot implies the gauge isn't connected to its sender. The gauge needle may "rest" in the full hot position even with the ignition off since there is no spring to return the needle to cold when not powered.
Exactly where is the sensor you found towards the rear passenger side of the engine... on the exhaust side of the cylinder head?? As Captkaos stated, the factory location for the engine temp sensor is in the side of the cylinder head between #1 and #3 cylinder exhaust ports.
I have a similar issue to this, mine is always stuck in the middle regardless of hot or cold.
Check power and ground to the gauge.
Thanks man, it will move toward hot when driving, but regardless it never goes down to cold when it is cold.
Sent from my VS990 using Tapatalk
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Ill take a look tonight and take pics of both locations.
Sounds like i need to pull the gauge regardless
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Thanks man, it will move toward hot when driving, but regardless it never goes down to cold when it is cold.
Temporarily ground the temp sensor lead to see if the gauge drops to cold.
Sounds like i need to pull the gauge regardless
Why?
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This is the spot in question. Slightly below and behind the red wire you can see the little head of hte sensor.
I'm now thinking this is oil pressure sensor
(http://i27.photobucket.com/albums/c177/teamcurtis/1978%20C10/380C12A4-1D5C-49C9-9343-AD2085694AD1_zpsksxnwn4g.jpg) (http://s27.photobucket.com/user/teamcurtis/media/1978%20C10/380C12A4-1D5C-49C9-9343-AD2085694AD1_zpsksxnwn4g.jpg.html)
Is this plug where a temp sensor should be?
(http://i27.photobucket.com/albums/c177/teamcurtis/1978%20C10/901C8612-2013-445A-97A8-1F3067CA8474_zpsi5uaiyzr.jpg) (http://s27.photobucket.com/user/teamcurtis/media/1978%20C10/901C8612-2013-445A-97A8-1F3067CA8474_zpsi5uaiyzr.jpg.html)
That plug is here between the #1 and #3 plugs
(http://i27.photobucket.com/albums/c177/teamcurtis/1978%20C10/ACA11473-CE36-4E0A-89E7-D9624DDC96BF_zpsehexjwux.jpg) (http://s27.photobucket.com/user/teamcurtis/media/1978%20C10/ACA11473-CE36-4E0A-89E7-D9624DDC96BF_zpsehexjwux.jpg.html)
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As I suspected, someone removed the cylinder heads from the engine and switched them side-to-side during reassembly. The sensor at right rear is the coolant temperature gauge sensor. You can either connect the gauge to the sensor where it is at the right rear, or move the sensor to the left front and swap the sensor for the pipe plug in the center image. The most accurate location for the sensor is at the left front due to proximity with the thermostat.
You should add heat shields between the exhaust manifold and the spark plugs to prevent rapid deterioration of the plug wire boots and arcing. The factory heat shields anchor under the 1/4" bolt at the bottom center margin of the center image.
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Thanks!
I doubt ill bother moving it now. If an engine were over heating it would still show the deviation of temp on that side as well correct? Ive never really used temp gauges as a reading, rather i know where the engine usually runs, and if its not there something is amiss.
If that's bad practice by all means put me on blast.
I have the heat shields and will be installing them before using the truck for any length of time. Considered using the socks as well.
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My personal opinion is that a temperature gauge is pointless if it isn't accurate. Nevertheless, most drivers use your approach of monitoring a gauge for "unusual" deviations from "normal."
I recommend that you take extra precautions to accommodate for increased temperature in the area of the sensor at the right rear. Air circulation in that area is not as effective due to shrouding and distance from the fan. Use SXL (https://www.delcity.net/catalogdetails?item=3718104) insulated wire, Thermo-Tec 14005 Thermo-Sleeve (https://www.summitracing.com/parts/the-14005) and a 90° silicone spark plug boot slipped over the sensor connector to shroud the plastic connector and wiring from heat soak.
Spark plug boot socks aren't necessary with cast manifolds and probably won't fit inside the factory heat shields - too thick. Headers create different requirements, because the thin tubular steel doesn't sink instantaneous spikes in temperature as well as the thick cast manifolds. So the heat in the vicinity of the plugs can be far more intense.
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Thanks man, it will move toward hot when driving, but regardless it never goes down to cold when it is cold.
Temporarily ground the temp sensor lead to see if the gauge drops to cold.
I grounded it on multiple locations and the gauge didnt budge. Im guess i have a bad gauge. Temp unit is new.
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Replace the gauge and burnish the harness-to-PC board and gauge clips-to-PC board connections. Use a soft pencil eraser or crocus cloth, but be very careful not to peel the copper foil loose from the flexible plastic board. You might need to increase the tension slightly between the clips and the PCB by gently bending the legs of the clips. Likewise on the harness connector terminals. It doesn't take much, so don't overdo it. Smear a sparing amount of antioxidant between the clips and the PCB.
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I finally ordered a new temp gauge and plugged it in.
It immediately reset to "cold". Grounded the wire and it shot up to "hot"
So it was a dead gauge. Wire Seems to be good. Need to test the sending unit before i wrap it all back up.
These plug wire shields are a PAIN!
are all 4 the same? I only seem to have two and need to order the other two.