Gas gauge needle flutter - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Greg63 · 10-17-2009, 05:26 PM

I don't know if this is a unique problem or not, but I did search through other threads and couldn't find a situation similar to mine.

In my '63, I installed a 21 gallon replacement gas tank under the bed. I used the sending unit that came with the tank, and it functions well - to a point.
The gas gauge reads accurately in respect to my fuel level. My problem is that the needles flutters VERY rapidly at random times. I just changed out the stock gauge with another stock gauge. The flutter is still there, just not as severe.
I know the signal from the sending unit is getting to the gauge, but I have no idea why the needle flutters.
Can anyone shed some light on this?
Greg.

Greg63 · 10-17-2009, 05:52 PM

I have also noticed that the gauge is normal (no flutter) when they key is on and the engine is not running.
Also, it is most noticeable at 1800 - 2000 rpm. At idle it seldom flutters, and above 2500 rpm it seems to be normal.
Is it possible that there is something in the alternator or tachometer that is interfering with the gauge?
Greg

*lakeroadster* · 10-17-2009, 05:57 PM

First thing I always check with any electrical glitch is the ground wire.

Run a temporary ground to a good source and see if the problem changes.

Greg63 · 10-17-2009, 06:02 PM

Thanks for that tip, but I have done that, too.
I had the tank out of the truck two weeks ago to check the sending unit - which seems to be fine.
At that time, I verified the ground from the tank, and today I checked the ground at the dash wiring harness.
Greg

daverod · 10-17-2009, 08:46 PM

63deluxfleet · 10-17-2009, 10:09 PM

haha my 63 does that too and today i ran outta gas! how embarassing huh? not to hijack but mine reads off some times and its killin me

daverod · 10-17-2009, 10:34 PM

I think we all need to fork out the 50 and get new sending units. na

63deluxfleet · 10-17-2009, 10:49 PM

haha no $h!t huh lol

daverod · 10-17-2009, 10:51 PM

Ya that would be to easy. Just pull it out a few more times and bend it some more.

*lakeroadster* · 10-18-2009, 07:51 AM

Here's a couple more idea:

A) You mentioned you installed a replacement tank. Your 1963 gas gauge needs a 30 ohm sending unit. Is the sending unit a 30 ohm or a 90 ohm?

B) I had a similar problem with the Tachometer needle in my '69 Camaro and I put a 10K, 1/2 watt resistor in the line and it calmed down the erratic readings. I don't know if this will help but I do know ithe resistor was only a couple bucks @ Radio Shack. Might be worth a try?

Greg63 · 10-18-2009, 01:25 PM

Quote:

Originally Posted by lakeroadster

Here's a couple more idea:

A) You mentioned you installed a replacement tank. Your 1963 gas gauge needs a 30 ohm sending unit. Is the sending unit a 30 ohm or a 90 ohm?

B) I had a similar problem with the Tachometer needle in my '69 Camaro and I put a 10K, 1/2 watt resistor in the line and it calmed down the erratic readings. I don't know if this will help but I do know ithe resistor was only a couple bucks @ Radio Shack. Might be worth a try?

I can only assume the sending unit is the correct 30 ohm piece. The needle actually reads properly and is accurately showing the true fuel level, it just decides to flutter from "F" to far right and back again.

I was thinking about adding a resistor, but had no idea where to start in respect to which one to use. I already have some from another project that I can try out. I will put one in and see what I get.
Greg.

Greg63 · 10-18-2009, 03:08 PM

Well. I just tried various resistors, from 1k - 4.7k, and all they did was bury the gas gauge needle to the right of "F".
I also tried disconnecting the signal wire from the tach - no change.

Any other ideas out there?
Greg.

Slow Build · 10-18-2009, 06:08 PM

Quote:

Originally Posted by lakeroadster

You mentioned you installed a replacement tank. Your 1963 gas gauge needs a 30 ohm sending unit. Is the sending unit a 30 ohm or a 90 ohm?

I was thinking the same thing. The tanks used in some conversions were made for the 1969-72 Blazer which would have had the 90 ohm unit. The conversion tanks for the 63-66 come with the 30 ohm unit.

Then again my gauge does basically the same thing and it's all stock so this may have nothing to do with it.

courage 80 · 10-18-2009, 11:41 PM

Here is my guess....

Does the new tank have baffles? The reading is correct when there is little to no vibration. When the truck hits the right range the gas vibrates and creates little waves in the tank. This would cause the needle to wave. Just a thought.

Greg63 · 10-20-2009, 08:15 PM

It has no baffles in it. I wondered the same thing.
I was trying to eliminate all other sources before I settled on that as the source of my problem.
Thanks.
Greg.

10-17-2009, 05:26 PM	#1
Greg63 Enjoy your truck Join Date: Oct 2007 Location: Newmarket, Ontario, Canada Posts: 1,066	Gas gauge needle flutter I don't know if this is a unique problem or not, but I did search through other threads and couldn't find a situation similar to mine. In my '63, I installed a 21 gallon replacement gas tank under the bed. I used the sending unit that came with the tank, and it functions well - to a point. The gas gauge reads accurately in respect to my fuel level. My problem is that the needles flutters VERY rapidly at random times. I just changed out the stock gauge with another stock gauge. The flutter is still there, just not as severe. I know the signal from the sending unit is getting to the gauge, but I have no idea why the needle flutters. Can anyone shed some light on this? Greg. __________________ 1 Corinthians 10:13 1963 Chevrolet 1/2 ton 2010 Camaro SS/RS 2014 Jeep Grand Cherokee 2016 Jeep Cherokee

10-17-2009, 05:52 PM	#2
Greg63 Enjoy your truck Join Date: Oct 2007 Location: Newmarket, Ontario, Canada Posts: 1,066	Re: Gas gauge needle flutter I have also noticed that the gauge is normal (no flutter) when they key is on and the engine is not running. Also, it is most noticeable at 1800 - 2000 rpm. At idle it seldom flutters, and above 2500 rpm it seems to be normal. Is it possible that there is something in the alternator or tachometer that is interfering with the gauge? Greg __________________ 1 Corinthians 10:13 1963 Chevrolet 1/2 ton 2010 Camaro SS/RS 2014 Jeep Grand Cherokee 2016 Jeep Cherokee Last edited by Greg63; 10-17-2009 at 05:54 PM.

10-17-2009, 05:57 PM	#3
lakeroadster Account Suspended Join Date: Sep 2009 Location: High Plains of Colorado Posts: 2,485	Re: Gas gauge needle flutter First thing I always check with any electrical glitch is the ground wire. Run a temporary ground to a good source and see if the problem changes. Last edited by lakeroadster; 10-17-2009 at 05:58 PM.

10-17-2009, 06:02 PM	#4
Greg63 Enjoy your truck Join Date: Oct 2007 Location: Newmarket, Ontario, Canada Posts: 1,066	Re: Gas gauge needle flutter Thanks for that tip, but I have done that, too. I had the tank out of the truck two weeks ago to check the sending unit - which seems to be fine. At that time, I verified the ground from the tank, and today I checked the ground at the dash wiring harness. Greg __________________ 1 Corinthians 10:13 1963 Chevrolet 1/2 ton 2010 Camaro SS/RS 2014 Jeep Grand Cherokee 2016 Jeep Cherokee

10-17-2009, 08:46 PM	#5
daverod SSN 706 Join Date: Mar 2009 Location: Pocatello Idaho Posts: 3,821	Re: Gas gauge needle flutter __________________ Daverods 64 C10 Daily driver 292 3 speed "Driver" Daverods 66 Build C10 Bags 350/350(On Hold) Daverods 52 Build 3100 S10 chassis,Bags, 350/700r4 "Click it" Last edited by daverod; 10-17-2009 at 08:52 PM.

10-17-2009, 10:09 PM	#6
63deluxfleet Registered User Join Date: Jun 2009 Location: dinuba, ca Posts: 623	Re: Gas gauge needle flutter haha my 63 does that too and today i ran outta gas! how embarassing huh? not to hijack but mine reads off some times and its killin me __________________ A girl phoned me the other day and said... Come on over, there's nobody home. I went over. Nobody was home. -Rodney Dangerfield .......THE ROAD TO HELL IS PAVED WITH GOOD INTENTIONS.....

10-17-2009, 10:34 PM	#7
daverod SSN 706 Join Date: Mar 2009 Location: Pocatello Idaho Posts: 3,821	Re: Gas gauge needle flutter I think we all need to fork out the 50 and get new sending units. na __________________ Daverods 64 C10 Daily driver 292 3 speed "Driver" Daverods 66 Build C10 Bags 350/350(On Hold) Daverods 52 Build 3100 S10 chassis,Bags, 350/700r4 "Click it"

10-17-2009, 10:49 PM	#8
63deluxfleet Registered User Join Date: Jun 2009 Location: dinuba, ca Posts: 623	Re: Gas gauge needle flutter haha no $h!t huh lol __________________ A girl phoned me the other day and said... Come on over, there's nobody home. I went over. Nobody was home. -Rodney Dangerfield .......THE ROAD TO HELL IS PAVED WITH GOOD INTENTIONS.....

10-17-2009, 10:51 PM	#9
daverod SSN 706 Join Date: Mar 2009 Location: Pocatello Idaho Posts: 3,821	Re: Gas gauge needle flutter Ya that would be to easy. Just pull it out a few more times and bend it some more. __________________ Daverods 64 C10 Daily driver 292 3 speed "Driver" Daverods 66 Build C10 Bags 350/350(On Hold) Daverods 52 Build 3100 S10 chassis,Bags, 350/700r4 "Click it"

10-18-2009, 07:51 AM	#10
lakeroadster Account Suspended Join Date: Sep 2009 Location: High Plains of Colorado Posts: 2,485	Re: Gas gauge needle flutter Here's a couple more idea: A) You mentioned you installed a replacement tank. Your 1963 gas gauge needs a 30 ohm sending unit. Is the sending unit a 30 ohm or a 90 ohm? B) I had a similar problem with the Tachometer needle in my '69 Camaro and I put a 10K, 1/2 watt resistor in the line and it calmed down the erratic readings. I don't know if this will help but I do know ithe resistor was only a couple bucks @ Radio Shack. Might be worth a try? Last edited by lakeroadster; 10-18-2009 at 08:01 AM.

10-18-2009, 03:08 PM	#12
Greg63 Enjoy your truck Join Date: Oct 2007 Location: Newmarket, Ontario, Canada Posts: 1,066	Re: Gas gauge needle flutter Well. I just tried various resistors, from 1k - 4.7k, and all they did was bury the gas gauge needle to the right of "F". I also tried disconnecting the signal wire from the tach - no change. Any other ideas out there? Greg. __________________ 1 Corinthians 10:13 1963 Chevrolet 1/2 ton 2010 Camaro SS/RS 2014 Jeep Grand Cherokee 2016 Jeep Cherokee

10-18-2009, 11:41 PM	#14
courage 80 Registered User Join Date: Sep 2007 Location: Colorado Springs Posts: 41	Re: Gas gauge needle flutter Here is my guess.... Does the new tank have baffles? The reading is correct when there is little to no vibration. When the truck hits the right range the gas vibrates and creates little waves in the tank. This would cause the needle to wave. Just a thought.

10-20-2009, 08:15 PM	#15
Greg63 Enjoy your truck Join Date: Oct 2007 Location: Newmarket, Ontario, Canada Posts: 1,066	Re: Gas gauge needle flutter It has no baffles in it. I wondered the same thing. I was trying to eliminate all other sources before I settled on that as the source of my problem. Thanks. Greg. __________________ 1 Corinthians 10:13 1963 Chevrolet 1/2 ton 2010 Camaro SS/RS 2014 Jeep Grand Cherokee 2016 Jeep Cherokee



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