Fuels gauge ohms - Page 3 - Chevy Nova Forum
Visit our sponsor, National Nostalgic Nova
 
Steve's Nova Site is an automotive enthusiast website dedicated to the 1962 - 1979 Chevrolet Nova, Chevy II and Acadian automobiles. We work together to preserve, restore, drive, show, race and provide fellowship for these classic cars. This is one of the best places to find information about parts, rebuilding, restoration and racing. This website is not affiliated with GM, General Motors or Chevrolet in any capacity.

Go Back   Chevy Nova Forum > Body, Chassis and Mechanical > Electrical


StevesNovaSite.com is the premier Chevrolet Nova Forum on the internet. Registered Users do not see the above ads.
Reply
 
Thread Tools Display Modes
Old 17th-June-2017, 02:48 PM   #31
sc2dave

Title: Nova Senior Member
iTrader: (0)
Status: Offline
Join Date: Dec 2008
Location: Los Angeles
Nova(s): 1966 nova, 194c.i.d.
Posts: 243
Quote:
Originally Posted by Custom Jim View Post










Jim
This is where my gauge sits at, when all wires are connected to send unit. I disconnected the wire to sending unit only, and it went about 1/2" past the full mark. I hooked it back up and ONLY disconnected the ground wire and it went back to the setting on the picture. Bad/sinking float?
  Reply With Quote
Sponsored Links
Advertisement
 
Old 17th-June-2017, 07:17 PM   #32
Ray_McAvoy
 
Ray_McAvoy's Avatar

Title: Nova Guru
iTrader: (0)
Status: Offline
Join Date: Feb 2004
Location: Sherman, Maine
Nova(s): 1974 & 1977
Posts: 1,712
Quote:
Originally Posted by bella's dad View Post
At the risk of sounding even more ignorant of electrical systems than I am, What is a "shunt"?
The "shunt" is a resistor that is connected in parallel with the gauge coil that pulls the needle toward the "empty" side. The sending unit (which is a variable resistor) is wired in parallel with the gauge coil that pulls the needle toward the "full" side.

On the original GM fuel gauges, the shunt resistor is typically mounted on the back of the gauge. Early ones were constructed of a thin wire wrapped around a rectangular insulator. Later ones are often in the form of a carbon film on a rectangular ceramic substrate.

If the shunt resistor is bad (open circuit), missing, or simply not making good electrical contact with the gauge terminals, it allows more current than normal to flow through the gauge's "empty" coil. That results in an abnormally low reading as shown in Jim's pictures.
  Reply With Quote
Old 17th-June-2017, 09:35 PM   #33
bella's dad
 
bella's dad's Avatar

Title: Nova Junior Member
iTrader: (0)
Status: Offline
Join Date: Sep 2015
Location: Hollister, CA
Nova(s): 1973 Hatchback
Posts: 81
Quote:
Originally Posted by Ray_McAvoy View Post
The "shunt" is a resistor that is connected in parallel with the gauge coil that pulls the needle toward the "empty" side. The sending unit (which is a variable resistor) is wired in parallel with the gauge coil that pulls the needle toward the "full" side.

On the original GM fuel gauges, the shunt resistor is typically mounted on the back of the gauge. Early ones were constructed of a thin wire wrapped around a rectangular insulator. Later ones are often in the form of a carbon film on a rectangular ceramic substrate.

If the shunt resistor is bad (open circuit), missing, or simply not making good electrical contact with the gauge terminals, it allows more current than normal to flow through the gauge's "empty" coil. That results in an abnormally low reading as shown in Jim's pictures.
Got it, thanks!
  Reply With Quote
 
Old 18th-June-2017, 12:45 PM   #34
sc2dave

Title: Nova Senior Member
iTrader: (0)
Status: Offline
Join Date: Dec 2008
Location: Los Angeles
Nova(s): 1966 nova, 194c.i.d.
Posts: 243
Quote:
Originally Posted by Ray_McAvoy View Post
The "shunt" is a resistor that is connected in parallel with the gauge coil that pulls the needle toward the "empty" side. The sending unit (which is a variable resistor) is wired in parallel with the gauge coil that pulls the needle toward the "full" side.

On the original GM fuel gauges, the shunt resistor is typically mounted on the back of the gauge. Early ones were constructed of a thin wire wrapped around a rectangular insulator. Later ones are often in the form of a carbon film on a rectangular ceramic substrate.

If the shunt resistor is bad (open circuit), missing, or simply not making good electrical contact with the gauge terminals, it allows more current than normal to flow through the gauge's "empty" coil. That results in an abnormally low reading as shown in Jim's pictures.
So,based on this, my shunt is probably bad? sending unit probably good, from my previous post?
  Reply With Quote
Old 18th-June-2017, 03:05 PM   #35
Custom Jim
 
Custom Jim's Avatar

Title: Moderator
iTrader: (2)
Status: Online
Join Date: Feb 2004
Location: Saint Louis MO.
Nova(s): 1968,1973,1974,1977(Sold)
Posts: 5,271
Garage
Quote:
Originally Posted by sc2dave View Post
So,based on this, my shunt is probably bad? sending unit probably good, from my previous post?
It's very possible it's bad or not making the proper connections.

The sender might be good or might not be.

I'm lucky in that I work for an audio shop and we do service work and I have access to different resistors. When I was testing mine and also holding school for another member at the house with his fuel gauge issues, I had a variety of resistors to where I could verify and check things. If you know how things work you can use the resistors to mimic what the sender in the tank should be outputting.

Years ago I had a customer that I installed a digital dash and it was wired to an adjustable tank depth sender and he was having issues and when I showed him how to test things in the trunk I didn't have to take the dash apart to where with the tests with the resistors, I could say for sure with 100% of confidence that from the test point towards the gauge was fine and he had a sender issue. I could have started by taking the dash apart but I tried to work smart with using a few tools like the resistors to check things prior to taking hard to access parts out of a dash.

You never know sometimes as you might have one issue or multiple ones but if you troubleshoot things properly, you can find single issue's or multiple ones.

Personally I would like to say for sure it's just a gauge shunt issue in your situation but now that I've said that, this will not be true.

Jim
__________________

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
  Reply With Quote
Old 18th-June-2017, 05:17 PM   #36
sc2dave

Title: Nova Senior Member
iTrader: (0)
Status: Offline
Join Date: Dec 2008
Location: Los Angeles
Nova(s): 1966 nova, 194c.i.d.
Posts: 243
Quote:
Originally Posted by Bmac View Post
I'll check and see if it's stamped on there tomorrow.
Is the stamping on the outside, where you can see it when the sender is installed?
  Reply With Quote
Old 18th-June-2017, 09:24 PM   #37
sc2dave

Title: Nova Senior Member
iTrader: (0)
Status: Offline
Join Date: Dec 2008
Location: Los Angeles
Nova(s): 1966 nova, 194c.i.d.
Posts: 243
So what should the shunt Ohms be when measured end to end,off of the gauge?
  Reply With Quote
Old 18th-June-2017, 10:03 PM   #38
Ray_McAvoy
 
Ray_McAvoy's Avatar

Title: Nova Guru
iTrader: (0)
Status: Offline
Join Date: Feb 2004
Location: Sherman, Maine
Nova(s): 1974 & 1977
Posts: 1,712
Quote:
Originally Posted by sc2dave View Post
So what should the shunt Ohms be when measured end to end,off of the gauge?
If I remember correctly, they are somewhere near 90Ω ... similar to the sending unit when full. If you don't get any reading at all (open circuit) then the shunt resistor is bad.
  Reply With Quote
Old 18th-June-2017, 11:53 PM   #39
sc2dave

Title: Nova Senior Member
iTrader: (0)
Status: Offline
Join Date: Dec 2008
Location: Los Angeles
Nova(s): 1966 nova, 194c.i.d.
Posts: 243
Quote:
Originally Posted by Ray_McAvoy View Post
If I remember correctly, they are somewhere near 90Ω ... similar to the sending unit when full. If you don't get any reading at all (open circuit) then the shunt resistor is bad.
I checked it and I got 920 or so. I noticed that it has the 2 prong connector and a 3rd threaded stud under. Is there something that connects to it? So then it's my sender that's most likely bad?
  Reply With Quote
Old 20th-June-2017, 10:36 PM   #40
Ray_McAvoy
 
Ray_McAvoy's Avatar

Title: Nova Guru
iTrader: (0)
Status: Offline
Join Date: Feb 2004
Location: Sherman, Maine
Nova(s): 1974 & 1977
Posts: 1,712
Quote:
Originally Posted by sc2dave View Post
I checked it and I got 920 or so.
Is that 920Ω or just a typo and supposed to be 92Ω ?

92Ω sounds okay, but if it really is reading 920Ω then something isn't right. Those resistors typically don't change in value (other than going open circuit if broken). So you might want to double check that measurement.

Quote:
Originally Posted by sc2dave View Post
I noticed that it has the 2 prong connector and a 3rd threaded stud under. Is there something that connects to it?
The 2 prong connector is for the power & sending unit connections. The 3rd threaded stud below connects the gauge to ground via the metal instrument cluster (the cluster is case ground).

Quote:
Originally Posted by sc2dave View Post
So then it's my sender that's most likely bad?
That depends on what you find when you double check the shunt resistor.
  Reply With Quote
Sponsored Links
Advertisement
 
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
VP Racing Fuels 9second540 Drag Racing Forum 16 14th-August-2012 11:18 PM
New Torco Race Fuels? 1974nova Drag Racing Forum 0 12th-September-2008 06:29 PM
69 Fuel gauge ohms? SuperNova69 Electrical 7 3rd-May-2007 09:44 PM
67 SS fuel sending unit resistance 30 or 90 ohms? Jetdoc 1st & 2nd Generation Chevy II/Nova's 3 22nd-June-2006 05:33 PM
Ohms for Fuel Cell Sender Question adidasink Electrical 5 28th-April-2006 09:17 PM


Site best viewed set to 1024 x 768.

All times are GMT -4. The time now is 11:22 PM.

Custom Designed for Steve's Nova Site by: vBSkinworks

 
Powered by vBulletin® Copyright ©2000 - 2017, Jelsoft Enterprises Lt
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
 

Garage Plus vBulletin Plugins by Drive Thru Online, Inc.