temperture gauge
Thread Starter
Racer
Joined: Sep 2005
Posts: 336
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From: staten island ny
temperture gauge
guys
my new vette 69 that i just purchase i notice the gauge moves but not much is there away i could test the gauge or the sending unit to make sure is working correct
thanks
my new vette 69 that i just purchase i notice the gauge moves but not much is there away i could test the gauge or the sending unit to make sure is working correct
thanks
Racer
Joined: Feb 2009
Posts: 265
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My guage used to sit around the middle, but would creep up on hot days. Since I got a new rad and elec fan with 180 thermostat and 180 sensor for the fan, my guage barely moves when it's warmed up too now. Figure it would come up more with 190 degree stuff in there. You may have a really good cooling system and you could check what thermostat you've got in there.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
remove the green wire from the sending unit ;; dash gauge needle should go to cold
next ground the green wire to the engine;; dash gauge needle should go to hot
edit- if your wanting to check calibration you will need to put a resistor between the green wire and ground. Do you have any resistors laying around ?
Last edited by ...Roger...; Aug 6, 2009 at 01:07 PM.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
Remove the sending wire from the temp sending unit. Turn the ignition key to ON [engine not running]. With the wire removed, the gauge should read full-scale in one direction. Now touch the metal connector on that wire to the engine block [electrical ground]; the gauge should read full-scale the other direction. If the gauge works as described, your problem is NOT with the gauge or the wiring. The problem is with the sending unit OR because you put some kind of insulating sealant on the threads of the sending unit [which are intended to provide the electrical ground to the temp sensing system via connection to the engine block].
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
You may already have a resistor- a 12v testlight. With an 1893 bulb in a testlight, remove the wire from the sender, ground the clip on the testlight and stick the point into the connector. turn the key on, the light should glow and the gauge should read 1/2 scale. Works for any GM electric gauge- Fuel level, temp, and oil pressure.
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,851
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
When the gauge stops moving what is the temperature? Telling us this will help figure out what is wrong.
Some of this has been covered above by everyone.
Test the ohms of the sending unit. Take a reading on the sender cold; take a reading on then sender when your thermostat opens. Depending on the thermostat you'll now have two readings to take from the sender in the car and this should give you a good idea if the sender is working. On average 106 ohms is 180 degrees
The dash unit will go to 100 degrees instant if it has power, ground and no signal. It will shoot over there in a flash.
It will do the same as mentioned above when you ground the input wire. It will shoot over to bury needle hot if you have a grounded ohms wire.
Your dash unit should require approximately these input readings to function. This will give you a starting point.
100 - 220 ohms
1st mark - 109
210 - 79 ohms
2nd mark - 65 ohms
250 - 51 ohms.
So test the output of the sender, verify the wire connection with the tests listed above and post again. There is a ton of knowledge between everyone that has posted to this tread. I’m sure we can figure you’re your problem.
Willcox
18243
Some of this has been covered above by everyone.
Test the ohms of the sending unit. Take a reading on the sender cold; take a reading on then sender when your thermostat opens. Depending on the thermostat you'll now have two readings to take from the sender in the car and this should give you a good idea if the sender is working. On average 106 ohms is 180 degrees
The dash unit will go to 100 degrees instant if it has power, ground and no signal. It will shoot over there in a flash.
It will do the same as mentioned above when you ground the input wire. It will shoot over to bury needle hot if you have a grounded ohms wire.
Your dash unit should require approximately these input readings to function. This will give you a starting point.
100 - 220 ohms
1st mark - 109
210 - 79 ohms
2nd mark - 65 ohms
250 - 51 ohms.
So test the output of the sender, verify the wire connection with the tests listed above and post again. There is a ton of knowledge between everyone that has posted to this tread. I’m sure we can figure you’re your problem.
Willcox
18243
Last edited by Willcox Corvette; Jan 18, 2010 at 04:30 PM.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
You may already have a resistor- a 12v testlight. With an 1893 bulb in a testlight, remove the wire from the sender, ground the clip on the testlight and stick the point into the connector. turn the key on, the light should glow and the gauge should read 1/2 scale. Works for any GM electric gauge- Fuel level, temp, and oil pressure.
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Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Hmmm you definitely have me at a disadvantage because I'm pretty stupid when it comes to reading the decimal place on an ohm meter. I guess I will have to go out in the garage and see if I can find an 1893 or 1895 bulb to measure. If it does measure 50 ohms that will still put the gauge around 250 degrees not half meter. Better yet I'll just put my test light in between the green wire and ground and see what the temp gauge reads.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
OK I measured a 10 ohm resistor from Radio Shack and it showed 10.1 on my meter. Then I measured an 1895 bulb and it showed 5.1 on my meter. I put the same bulb in my test light and put the test light between the green temp sender wire and ground and the temp gauge read 280 + degrees.
Burning Brakes
Joined: Jul 2009
Posts: 1,132
Likes: 14
From: A town SC
You may already have a resistor- a 12v testlight. With an 1893 bulb in a testlight, remove the wire from the sender, ground the clip on the testlight and stick the point into the connector. turn the key on, the light should glow and the gauge should read 1/2 scale. Works for any GM electric gauge- Fuel level, temp, and oil pressure.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Not so fast. A test light is going to be a fixed resistance.
1/2 scale on the temp gauge would be 190 degrees and that would take around 95 ohms
1/2 scale on the fuel gauge would take around 45 ohms
How can the test light provide 45 ohms for one and 95 ohms on the other ?
1/2 scale on the temp gauge would be 190 degrees and that would take around 95 ohms
1/2 scale on the fuel gauge would take around 45 ohms
How can the test light provide 45 ohms for one and 95 ohms on the other ?
Last edited by ...Roger...; Aug 7, 2009 at 12:54 AM.
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,851
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Tim,
This has me perplexed too! I’m not trying to argue but I’m not sure how this is possible on the temp gauge.
Half the gauge on this temp gauge would be around 80 ohm's,
100 - 220 ohms
1st mark - 109
210 - 79 ohms (this is the 1/2 way point on this gauge)
2nd mark - 65 ohms
250 - 51 ohms.
Half the gauge on fuel would be 45 ohms as would be temp sender and oil pressure.
I'm not sure how a 1893 bulb would get you an correct reading on the non linear temp gauge? Especially when different gauges have a different face with different input required to get to the 1/2 way point.
I don’t know what the resistance of this bulb when installed in a test lamp. But it is not possible for one resistor to register ½ a gauge on all GM gauges. . . Fuel, Oil Temp, and Oil pressure it is possible but not on the temp gauge.
Willcox
This has me perplexed too! I’m not trying to argue but I’m not sure how this is possible on the temp gauge.
Half the gauge on this temp gauge would be around 80 ohm's,
100 - 220 ohms
1st mark - 109
210 - 79 ohms (this is the 1/2 way point on this gauge)
2nd mark - 65 ohms
250 - 51 ohms.
Half the gauge on fuel would be 45 ohms as would be temp sender and oil pressure.
I'm not sure how a 1893 bulb would get you an correct reading on the non linear temp gauge? Especially when different gauges have a different face with different input required to get to the 1/2 way point.
I don’t know what the resistance of this bulb when installed in a test lamp. But it is not possible for one resistor to register ½ a gauge on all GM gauges. . . Fuel, Oil Temp, and Oil pressure it is possible but not on the temp gauge.
Willcox
Last edited by Willcox Corvette; Aug 7, 2009 at 10:10 PM.
Burning Brakes
Joined: Jul 2009
Posts: 1,132
Likes: 14
From: A town SC
not so fast.
Not so fast. A test light is going to be a fixed resistance.
1/2 scale on the temp gauge would be 190 degrees and that would take around 95 ohms
1/2 scale on the fuel gauge would take around 45 ohms
How can the test light provide 45 ohms for one and 95 ohms on the other ?
1/2 scale on the temp gauge would be 190 degrees and that would take around 95 ohms
1/2 scale on the fuel gauge would take around 45 ohms
How can the test light provide 45 ohms for one and 95 ohms on the other ?
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Le Mans Master
Joined: Oct 2006
Posts: 7,123
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From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
Guys, I started checking gauge operation with a test light like I described about 35 years ago when I was working as a mechanic in a Chevy dealer. It's not supposed to be an exact accurate test- If you want that you need to set up a test box with a variable potentiometer and calibrate it. It just does a quick and dirty test of the circuit. If the gauge and wiring is good, the testlight will make about 1/2 scale sometimes a little more, sometimes a little less. If the gauge dosen't move and you can prove power to the gauge, the gauge is bad. If the gauge moves that way and not when the sender is hooked up, the sender is bad.If the gauge won't move either way, chase the wire.
Remember too, that getting paid flat rate kind of forces you to come up with quick tests. the faster you get something fixed, the faster you move to the next job, and the more money you make.
Remember too, that getting paid flat rate kind of forces you to come up with quick tests. the faster you get something fixed, the faster you move to the next job, and the more money you make.
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,851
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Tim-
I hope you didn’t take my post the wrong way. I don’t know the resistance on that bulb and knowing the inputs required for each gauge, well it just did not make sense. Your test will tell you if the gauge is reading the ohms.
I can appreciate the instinctive genius to find things that work faster. Victor in my shop has that kind of mind!
Dwnnch’s flasher test on an old post was one of the classics too! I’ve never tested a flasher for resistance and would have never thought of it either.
Willcox
I hope you didn’t take my post the wrong way. I don’t know the resistance on that bulb and knowing the inputs required for each gauge, well it just did not make sense. Your test will tell you if the gauge is reading the ohms.
I can appreciate the instinctive genius to find things that work faster. Victor in my shop has that kind of mind!
Dwnnch’s flasher test on an old post was one of the classics too! I’ve never tested a flasher for resistance and would have never thought of it either.
Willcox
Racer
Joined: Feb 2009
Posts: 265
Likes: 0
Guage drops to 0 if I pull the wire off the sender, and pegs itself if I ground it. When the engine is warmed up, I get 52 Ohms with a 180 thermostat.
Shouldn't that put me around the second mark on the guage between 210 and 250 and I'm barely off the first mark when warmed up?
I also get 52 Ohms whether I read the resistance with my multimeter ground wire on the body of the sender or on the intake manifold. Wouldn't that be a good test to see if sealant/teflon tape is causing resistance/bad ground for the sender ?
Last edited by kunkle; Aug 9, 2009 at 07:55 PM.
