Gas Gauge & Cigarette lighter problems - Impala Tech
Electrical & Wiring Troubleshooting electrical problems

 
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post #1 of 10 (permalink) Old 03-07-2015, 02:52 PM Thread Starter
 
 
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Unhappy Gas Gauge & Cigarette lighter problems

Hello everyone,

It's been a while since I posted something, had to create a new account. I was hoping I can get some answers. I have a 1968 Impala. My first problem is that the fuel gauge is not reading fuel levels. I have read some of the forums here and it was mentioned that a ground wire being corroded behind the license plate can be the cause. I am unable to locate it and not sure what to do once I find it to fix that problem. Are there other things that could be causing the problem? My second issue is that I am not getting any power from my cigarette lighter? I'm not sure if it's a fuse or wiring issue.

Any help will be greatly appreciated it.

Thank you

Jon
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post #2 of 10 (permalink) Old 03-07-2015, 03:21 PM
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Welcome back Jon!

The fuse is easiest to check. It will be where the fuse box says CIG.

The fuel gauge is just a volt meter. It reads full power to ground through a variable resister called a Rheostat (a bunch of resistance wire wrapped around an insulating non-flammable material that allows for a lot of resistance if all of the windings are included or low if only a few). A contact point sweeps across the surface of the coils to complete the designed circuit.

Where a problem arises is if rust interferes with the rest of the circuit The part not included in the original design. If you remove the ground strap and clean all points of contact it should function as intended. Of course that assumes rust is the problem and not something else, though usually it is.

Big Dave
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post #3 of 10 (permalink) Old 03-08-2015, 10:30 AM
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The ground wire for the sending unit is located in front of the tank on the body above the rear axle. There is a black wire screwed to the body, this is where the connection corrodes.
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post #4 of 10 (permalink) Old 03-08-2015, 02:09 PM Thread Starter
 
 
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Thanks fellas. I will take a look tomorrow and let you know what I find.

Jon
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post #5 of 10 (permalink) Old 03-11-2015, 02:32 AM Thread Starter
 
 
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Hello again. Wanted to follow up with y'all on my situation. Upon inspecting the fuse box located under the steering column, I found no fuse that states cig. But I did take a look at the actual cigarette lighter and it seems to have been burned out some point. So I figures I would start there. Now I just need to purchase it. For my fuel gauge issue, have not had the opportunity of troubleshooting it. I am curious tho, if it's not a rusted ground wire. Would it be safe to assume its a defective fuel sending unit?

Thanks!

Jon
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post #6 of 10 (permalink) Old 03-11-2015, 08:05 AM
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Pretty good assumption but my guess would be the ground.
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post #7 of 10 (permalink) Old 03-11-2015, 02:28 PM
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Quote:
Originally Posted by JonFernandez305 View Post
Hello again. Wanted to follow up with y'all on my situation. Upon inspecting the fuse box located under the steering column, I found no fuse that states cig. But I did take a look at the actual cigarette lighter and it seems to have been burned out some point. So I figures I would start there. Now I just need to purchase it. For my fuel gauge issue, have not had the opportunity of troubleshooting it. I am curious tho, if it's not a rusted ground wire. Would it be safe to assume its a defective fuel sending unit?

Thanks!

Jon
If someone stuck a metallic object into the cigar lighter it could have shorted out the Nickel-Chrome wire used as a heating element. You can buy a replacement cigar lighter at most corner discount auto parts stores to replace the one that no longer works (you can also buy used small parts from junk yards that specialize in old hard to find parts).

If someone was using the cigar lighter as a power tap and the device drew more than 30 Amps; or it was improperly wired so as to cause a short, then it pops the 30 Amp AGC Buss fuse in the fuse box (the glass style fuse with flat metal ends). The circuit is also protected by the main wiring's 50 Amp fusible link that is a fast blow so you will usually also pop that if the wiring has a short anywhere.

Big Dave
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post #8 of 10 (permalink) Old 03-11-2015, 03:23 PM
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For the cigar lighter it can also be the positive contact inside the dash part that's dirty or corroded, it was not working in my car as well and after cleaning it with a wire brush on my dremel works fine now. Just don't forget to disconnect the positive wire at the back of the housing or battery or you'll short it out.
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post #9 of 10 (permalink) Old 03-16-2015, 12:47 PM Thread Starter
 
 
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Hello friends,

Did a little bit of troubleshooting today. I found the ground wire for the gas tank near the axle. I was unable to remove the bolt that had the ground wire strapped to the frame. I tried cleaning it with some rust remover and a wire brush to remove as much corrosion as possible but that did not help. I got desperate and decided to cut the wire and attach a wire to that one and find another grounding point and still no luck. I am wondering if I need an actual grounding strap to make a good contact attached to the frame. Any suggestions?

Thank you

Jon
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post #10 of 10 (permalink) Old 03-17-2015, 02:11 PM Thread Starter
 
 
Join Date: Mar 2015
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Took the Impala to a shop today. They hooked up an actual grounding strap and still no luck. I am going to order the replacement fuel sending unit and give that a shot.
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1968 impala, cigarette lighter, fuel gauge wrong reading

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