78 C3 amp gauge Problem
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From: Dayton Nevada
78 C3 amp gauge Problem
I started our project car for the first time yesterday. I found the amp gauge was not working. I used a volt meter and checked at the battery, 13.5 volts...The c3 has one of those plastic printed circuits on the back and it would seem fool proof to hook it up. However, the odd chance I could have. Is there a right or wrong way to attach the small nuts on the threaded studs, Insulators, etc,...
I have New wire harness front and back.
Dose anyone have a photo showing a connection????
Of course it could be just a bad gauge.
I read where a "AAA" battery is crossed at terminals to check if it is alive, will try that.
I have New wire harness front and back.
Dose anyone have a photo showing a connection????
Of course it could be just a bad gauge.
I read where a "AAA" battery is crossed at terminals to check if it is alive, will try that.
Le Mans Master
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From: McHenry Illinois
I'll be surprised if your 78 has an ammeter, should be a volt meter.
http://willcoxcorvette.com/product_i...ducts_id=26351
http://willcoxcorvette.com/product_i...ducts_id=26351
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OK..Volt meter....the gauge that goes from 0-13,, sits in the lower right hand Conner of the cluster....I applied a AAA battery and the needle moved a little like a plus. Touched it to the car battery and it went all the way over.
Re-connected it and nothing....also now gas gauge only shows full.
Re-connected it and nothing....also now gas gauge only shows full.
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Joined: Jun 2012
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From: Dayton Nevada
I'll be surprised if your 78 has an ammeter, should be a volt meter.
http://willcoxcorvette.com/product_i...ducts_id=26351
http://willcoxcorvette.com/product_i...ducts_id=26351
Question ? on the back of the unit there is shown a printed circuit board??? where the low fuel light is. I have something like that but it is not attached, I thought it was for the tachometer.
I see on the pic of the circuit ground connections to harness plug for Gen, Low Fuel,lamps upper. but not for the lamps and AMP gauge.
IS the ground accomplished by a jumper wire to one of the circuit gound connections???
Last edited by Douglas Brown; May 26, 2014 at 07:55 PM.
Le Mans Master
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From: McHenry Illinois
Sometimes when the low fuel module goes bad, the hole gets left blank, don't put a bulb in that place instead, it will stay on.
You can't test the volt meter with a AAA battery, it takes car battery voltage. The AAA battery is for testing an ammeter from earlier years.
You can't test the volt meter with a AAA battery, it takes car battery voltage. The AAA battery is for testing an ammeter from earlier years.
Last edited by '75; May 26, 2014 at 05:00 PM.
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From: Dayton Nevada
Please look at photo's to follow, they are from my car.
Printed circuit board,
Small circuit board what does it go to, or where dose it attach..if any where...ANSWER it is a Tachometer circuit board.
Printed circuit board,
Small circuit board what does it go to, or where dose it attach..if any where...ANSWER it is a Tachometer circuit board.
Last edited by Douglas Brown; May 27, 2014 at 07:41 PM.
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Please out photos in thread
Le Mans Master
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From: McHenry Illinois
Seems like part of your circuit board(low fuel module) is missing. In your pic, the grey bulb holder in the upper left should be removed. That is where the circuit board is installed, but part of it is missing. I recommend you get ahold of willcox to see if they can help.
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From: Dayton Nevada
Thanks
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with the instrument cluster removed the fuel gauge is pegged past Full, the Volt meter is below 8 and stays there.
The resistors are different colors, Fuel is blue, the others are red/orange type color. does it make a difference?
The resistors are different colors, Fuel is blue, the others are red/orange type color. does it make a difference?
Le Mans Master
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From: McHenry Illinois
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Still have a problem with AMP/VOLT meter/gauge....I guess it would be Volt meter even thought paper work calls it an AMP gauge.
Here the problem..it is pegged to the far right, does not move when mounted in cluster and hooked up to the harness connecter.
I tested it by placing two leads +/- two the battery and then to the terminals to watch for a response. It moved across the face and back as I moved the leads.
It is supposed to be grounded to the cluster housing, I checked the connection it's correct
The face of these meters are showing 8-18 volts it dose not show discharge as in - #'s so when it is working it should show volts generated only. I checked at the battery with a load tester and it was charging 13.5....
MAYBE it needs a jumper wire to the temp gauge, ground to work.??????
Here the problem..it is pegged to the far right, does not move when mounted in cluster and hooked up to the harness connecter.
I tested it by placing two leads +/- two the battery and then to the terminals to watch for a response. It moved across the face and back as I moved the leads.
It is supposed to be grounded to the cluster housing, I checked the connection it's correct
The face of these meters are showing 8-18 volts it dose not show discharge as in - #'s so when it is working it should show volts generated only. I checked at the battery with a load tester and it was charging 13.5....
MAYBE it needs a jumper wire to the temp gauge, ground to work.??????
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I will try again tomorrow with the volt gauge....It has to be a bad ground, but it is hooked up correctly. with sm washer then nut, then prt circuit, then sm nut. some where it is not picking up a ground connection from the case or one of the other grounds. If this is true then I will run a jumper to another ground and see what happens.
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The left side of the harness connecter is the passenger...the right side is Driver
as can be seen there is NO power to (3) three of the tabs that fit in the slot.
There is one GOOD power tab to the clock.
Now I am confused as to why there is not power in a new wire harness.
Gauges look like this when on bench
When ignition is on and motor is running, notice gen light is on...
load tester indicates charging system working
I looked at the fuses (pulled gauge fuse ) and tested with test light ...ok
why other power leads are dead????
as can be seen there is NO power to (3) three of the tabs that fit in the slot.
There is one GOOD power tab to the clock.
Now I am confused as to why there is not power in a new wire harness.
Gauges look like this when on bench
When ignition is on and motor is running, notice gen light is on...
load tester indicates charging system working
I looked at the fuses (pulled gauge fuse ) and tested with test light ...ok
why other power leads are dead????
Last edited by Douglas Brown; May 30, 2014 at 04:49 PM.
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will re-check fuses tomorrow
also connected tachometer, it dose not move up or down.
Last edited by Douglas Brown; May 30, 2014 at 10:51 PM.
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Just a note: one of the fuse terminals on the back side of the fuse box was corroded and not making good contact which caused "no power" at certain circuits.....
and the ignition switch (not the Key-switch, but the switch with the main dash harness plugged into it) was worn internally and one of the contacts was giving intermittent power.
and the ignition switch (not the Key-switch, but the switch with the main dash harness plugged into it) was worn internally and one of the contacts was giving intermittent power.
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Just a note: one of the fuse terminals on the back side of the fuse box was corroded and not making good contact which caused "no power" at certain circuits.....
and the ignition switch (not the Key-switch, but the switch with the main dash harness plugged into it) was worn internally and one of the contacts was giving intermittent power.
and the ignition switch (not the Key-switch, but the switch with the main dash harness plugged into it) was worn internally and one of the contacts was giving intermittent power.