Topic: Temp Gauge
in Forum: C3 Electrical
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I need some educated guesses here.
|UPDATED|7/23/2013 7:50:43 PM (AZT)|/UPDATED|
My Temp gauge is giving me fits. Sometimes the needle just hangs, straight down. Usually it appears to work properly.
Yesterday I took the car to my mechanic. He noticed that the temp gauge wasn't working and he had one in his inventory. He ordered one for some poor soul who didn't want to pay the $150 labor to install the part.
Tonight I fire up the vette and the gauge is working again. Arghhhhh!
So here's the question. Has anyone ever seen this behavior? My inclination is to go ahead and replace the gauge. Heck, I have part of the instrument bezel torn apart anyway. Or... do you electrical experts think the gauge is fine and it's a waste of money to replace it?
What do you think?
|UPDATED|7/23/2013 7:50:43 PM (AZT)|/UPDATED|
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Lifetime MemberModerator
Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20214
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
I would first make sure the problem is not in the temp sender unit, or the wire for it. The sending unit is in the driver side head, and normally has a green wire on it. Disconnect the wire, and ground it directly to the engine. Turn the key on, and the temp gauge should peg full HOT. With the wire disconnected, the gauge should go full COLD. If the gauge responds properly with this test, the problem is more likely a bad sending unit.
|UPDATED|7/23/2013 7:39:37 PM (AZT)|/UPDATED|
Sometimes the green wire can get too close to the exhaust manifold, and burn the insulation, and then short out as you drive, making the gauge do weird things.
I would check that stuff before condemning the gauge. 
|UPDATED|7/23/2013 7:39:37 PM (AZT)|/UPDATED|
Joel Adams
C3VR Lifetime Member #56 
My Link 
(click for Texas-sized view!) NCRS
"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
Thanks so much.
The gauge shudders when it's showing heat over 200 degrees. When the car was completely stopped the gauge hung straight down. When I started it out tonight it came back like a Jack In The Box.
So I went to the garage to perform this test. I don't find any wire of any kind coming from the head. Sigh... Tomorrow's another day.
I do appreciate your response. I now get to figure out where Bubba attached the wire. Smile...
Water temp sending unit in head (Near spark plug) should look something like this:
http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_temperature-sending-unit-wells-vehicle-electronics_10305740-p?searchTerm=water+temperature+sending+unit
If you find it then look for wire that goes to it.
http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_temperature-sending-unit-wells-vehicle-electronics_10305740-p?searchTerm=water+temperature+sending+unit
If you find it then look for wire that goes to it.
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DanT
Thank you, that helps. I should be able to find it using my handy dandy telescoping mirror. I appreciate the specific instructions.
The learning curve is really steep right now. I've been a C3 owner for all of three months and it's been a very long time since I've done much of my own car maintenance. I'm starting to blow off the dust and cobwebs. It's great doing this as a hobby, not a job.
BTW: I'm a Ph.D. in adult education. This sort of confusion followed by enlightenment followed by pulling up old memories is really REALLY good for those of us who are... err... experienced in life. 
14
Lifetime MemberModerator
Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20214
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
Yup...good ol #14! It MAY be in the passenger side head on the '72 automatic...not 100% sure if those had the TCS(Transmission Controlled Spark) system. If you see the sender on the pass side, and it has TWO wires, that is for the TCS...if it only has ONE wire, that is your temp gauge sender. The gauge wire will always be a dark green color, unless someone has been fiddlin with it.
(Thanks Bob!)
(Thanks Bob!
)Joel Adams
C3VR Lifetime Member #56
My Link
(click for Texas-sized view!) NCRS
"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
Lifetime MemberLa Quinta, CA - USA
Joined: 3/19/2008
Posts: 53
Vette(s): 1968 convertible, small block, auto, pw, pb, ps, air, 3rd owner CA black plate
Here is a link to a Wilcox video that is a pretty good explanation of testing the temp gauge.
best of luck to you!
Bob
Problem solved thanks to you guys. Of course the sending unit is under a chrome shield so it's next inaccessible to anyone over the age of 10.
When I did touch the wire it immediately broke free of the clip holding it to the sending unit. I refurbished the clip, reattached the wire and presto... no more temp gauge problems!
in Forum: C3 Electrical
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