Temperature gauge issues
Thread Starter
Instructor
Joined: Dec 2007
Posts: 128
Likes: 1
From: Gulfport Ms.
Temperature gauge issues
Hello.
I'm finishing up the 496 stroker swap into my '79. I have the factory temperature gauge, when I went to install the sending unit from my 350 into the intake manifold the hole was too large for the sending unit. I went to the parts house and got a sending unit for a '74 454 car (sending unit for a gauge, not light) and it fit the manifold. Now when I turn the key on, car completely cold, the gauge reads around 120-130 degrees before ever even starting it. The gauge operates once the engine is started, but seems to read quite high. I let the car idle for a little while today and the gauge quickly rose to around 230 degrees, the radiator cap was off and I had flow, I used a thermometer to measure water temp in the radiator and it showed 187 degrees, I used my temp gun to pull a reading off the head and manifold surface and it showed around 150 degrees. Could it be that the older sending unit isn't compatible with my gauge? I could just get an aftermarket gauge, but would like to sort this just to know more about it. Thanks in advance for any opinions.
I'm finishing up the 496 stroker swap into my '79. I have the factory temperature gauge, when I went to install the sending unit from my 350 into the intake manifold the hole was too large for the sending unit. I went to the parts house and got a sending unit for a '74 454 car (sending unit for a gauge, not light) and it fit the manifold. Now when I turn the key on, car completely cold, the gauge reads around 120-130 degrees before ever even starting it. The gauge operates once the engine is started, but seems to read quite high. I let the car idle for a little while today and the gauge quickly rose to around 230 degrees, the radiator cap was off and I had flow, I used a thermometer to measure water temp in the radiator and it showed 187 degrees, I used my temp gun to pull a reading off the head and manifold surface and it showed around 150 degrees. Could it be that the older sending unit isn't compatible with my gauge? I could just get an aftermarket gauge, but would like to sort this just to know more about it. Thanks in advance for any opinions.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,112
From: Crossville TN
Either the sender is not the correct unit for your gauge....or the gauge has been changed sometime in the past. You can try a different sender. I believe that lectriclimited.com has the correct sender for your car. Or you can measure the resistance of the sender (output pin to engine [ground]) at both "cold" condition and when warmed up fully. If you provide that info, I could recommend a resistor to add to the wiring which would properly calibrate your gauge.
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
I'm finishing up the 496 stroker swap into my '79. I have the factory temperature gauge, when I went to install the sending unit from my 350 into the intake manifold the hole was too large for the sending unit. ....Could it be that the older sending unit isn't compatible with my gauge?.
Assuming your OLD 79 sender was working OK with your 79 gage ... go back to parts store & get a reducing bushing adapter to fit the small sender into a larger hole ... then reinstall your OLD 79 sender ... very common issue & most common solution. If you don't KNOW what impedence is of both sender & gage (& cannot match via impedence) ... then match via same year to same year. AFAIK, lectric limited does Not offer small senders that're impedence matched to early gages.
-edit- BTW a bud with a correct ss396 68 camaro moved his sender from head to intake ... it didn't read right ... chased problem a LONG time until simply moving sender back to head ... all AOK now.
Last edited by jackson; Sep 9, 2008 at 02:59 PM.
Thread Starter
Instructor
Joined: Dec 2007
Posts: 128
Likes: 1
From: Gulfport Ms.
Either the sender is not the correct unit for your gauge....or the gauge has been changed sometime in the past. You can try a different sender. I believe that lectriclimited.com has the correct sender for your car. Or you can measure the resistance of the sender (output pin to engine [ground]) at both "cold" condition and when warmed up fully. If you provide that info, I could recommend a resistor to add to the wiring which would properly calibrate your gauge.
What you have now ain't compatible.
Assuming your OLD 79 sender was working OK with your 79 gage ... go back to parts store & get a reducing bushing adapter to fit the small sender into a larger hole ... then reinstall your OLD 79 sender ... very common issue & most common solution. If you don't KNOW what impedence is of both sender & gage (& cannot match via impedence) ... then match via same year to same year. AFAIK, lectric limited does Not offer small senders that're impedence matched to early gages.
-edit- BTW a bud with a correct ss396 68 camaro moved his sender from head to intake ... it didn't read right ... chased problem a LONG time until simply moving sender back to head ... all AOK now.
Assuming your OLD 79 sender was working OK with your 79 gage ... go back to parts store & get a reducing bushing adapter to fit the small sender into a larger hole ... then reinstall your OLD 79 sender ... very common issue & most common solution. If you don't KNOW what impedence is of both sender & gage (& cannot match via impedence) ... then match via same year to same year. AFAIK, lectric limited does Not offer small senders that're impedence matched to early gages.
-edit- BTW a bud with a correct ss396 68 camaro moved his sender from head to intake ... it didn't read right ... chased problem a LONG time until simply moving sender back to head ... all AOK now.
Thread Starter
Instructor
Joined: Dec 2007
Posts: 128
Likes: 1
From: Gulfport Ms.
actually yes, I used teflon tape, I didn't even think of the ground issue. Thanks, I'll be sure to put the original sending unit and bushing in without the tape this evening after work.
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Thread Starter
Instructor
Joined: Dec 2007
Posts: 128
Likes: 1
From: Gulfport Ms.
I put a few in an album, I hope I did it right. It's not much to look at yet but I will get to the pretty part when the time comes.
Last edited by wesleyshawn; Sep 9, 2008 at 08:39 PM.