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.

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

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.

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

Re: Gas gauge needle flutter
 

;)

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

Re: Gas gauge needle flutter
 

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

Re: Gas gauge needle flutter
 

haha no $h!t huh lol

Re: Gas gauge needle flutter
 

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

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?

Re: Gas gauge needle flutter
 

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.

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.

Re: Gas gauge needle flutter
 

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.

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.

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.