Club Cobra GasN Exhaust  

Go Back   Club Cobra > Cobra Talk Areas > ALL COBRA TALK

Welcome to Club Cobra!  The World's largest non biased Shelby Cobra related site!

  •  » Representation from nearly all Cobra/Daytona/GT40 manufacturers
  •  » Help from all over the world for your questions
  •  » Build logs for you and all members
  •  » Blogs
  •  » Image Gallery
  •  » Many thousands of members and nearly 1 million posts! 

YES! I want to register an account for free right now!  p.s.: For registered members this ad will NOT show

Keith Craft Racing
Nevada Classics
Keith Craft Racing
Main Menu
Module Jump:
Nevada Classics
Nevada Classics
MMG Superformance
Keith Craft Racing
Advertise at CC
Banner Ad Rates
MMG Superformance
Keith Craft Racing
MMG Superformance
August 2020
S M T W T F S
            1
2 3 4 5 6 7 8
9 10 11 12 13 14 15
16 17 18 19 20 21 22
23 24 25 26 27 28 29
30 31          
  #1 (permalink)  
Old 07-11-2020, 04:31 PM
767Jockey's Avatar
Senior Club Cobra Member
Visit my Photo Gallery

 
Join Date: Feb 2005
Cobra Make, Engine: Contemporary, FE, Tremec TKO 600
Posts: 1,676
Not Ranked     
Default Starting to troubleshoot my inop dash gauge lighting

My dash gauges are Smiths, using a rotary rheostat type lighting switch. Given that electrical is definitely my least knowledgeable area, I could use a bit of help troubleshooting this.

On the back of the rotary switch/dimmer that controls the gauge lighting, there are only two wires. Am I correct in thinking that if I jump across these two wires, the lights should come on if the switch is bad, effectively closing the circuit and taking the switch out of the circuit. Then, if the lights don't come on I would have to investigate further as it's likely an issue in the circuitry?
Reply With Quote
Sponsored Links
Sponsored Links
  #2 (permalink)  
Old 07-11-2020, 04:43 PM
twobjshelbys's Avatar
CC Member
Visit my Photo Gallery

 
Join Date: Jan 2009
Location: Las Vegas, NV
Cobra Make, Engine: Shelby CSX4005LA, Roush 427IR
Posts: 3,861
Not Ranked     
Default

Or to be safe disconnect the hot lead of the switch (pull the fuse) and use an ohm-meter across the leads of the switch while turning and closing the switch.
__________________
Cheers,
Tony
CSX4005LA
Reply With Quote
  #3 (permalink)  
Old 07-11-2020, 06:42 PM
ERA 626's Avatar
CC Member
Visit my Photo Gallery

 
Join Date: Sep 2001
Location: Danville, CA
Cobra Make, Engine: CSX 6079 482CI CSX cross ram
Posts: 1,120
Not Ranked     
Default

Quote:
Originally Posted by twobjshelbys View Post
Or to be safe disconnect the hot lead of the switch (pull the fuse) and use an ohm-meter across the leads of the switch while turning and closing the switch.
what would that do? you say " ohm meter" are you implying checking for resistance across the 2 wires? Im confused...
Reply With Quote
  #4 (permalink)  
Old 07-11-2020, 07:47 PM
Gaz64's Avatar
CC Member
Visit my Photo Gallery

 
Join Date: May 2008
Location: Brisbane, QLD
Cobra Make, Engine:
Posts: 2,460
Not Ranked     
Default

Quote:
Originally Posted by ERA 626 View Post
what would that do? you say " ohm meter" are you implying checking for resistance across the 2 wires? Im confused...
With the hot lead (12v positive) disconnected from the rheostat input, we can then read the rheostat resistance with an ohmmeter while moving the rheostat dial.

I would check for 12v positive at the input lead with a voltmeter, DVM or DMM, digital voltmeter/digital multimeter.

Gary
__________________
Gary

Gold Certified Holden Technician
Reply With Quote
  #5 (permalink)  
Old 07-11-2020, 08:17 PM
twobjshelbys's Avatar
CC Member
Visit my Photo Gallery

 
Join Date: Jan 2009
Location: Las Vegas, NV
Cobra Make, Engine: Shelby CSX4005LA, Roush 427IR
Posts: 3,861
Not Ranked     
Default

Quote:
Originally Posted by Gaz64 View Post
With the hot lead (12v positive) disconnected from the rheostat input, we can then read the rheostat resistance with an ohmmeter while moving the rheostat dial.

I would check for 12v positive at the input lead with a voltmeter, DVM or DMM, digital voltmeter/digital multimeter.

Gary
What he said.

Except I still have my Radio Shack VOM with a dial meter. Still in the original box. It's got to be close to 50 years old now. Works fine, has lasted a long time. I had a Heathkit VTVM but it was too large and clumsy for most things. I used it when building the Heathkit TV but I think I gave it to Goodwill decades ago.
__________________
Cheers,
Tony
CSX4005LA

Last edited by twobjshelbys; 07-11-2020 at 08:21 PM..
Reply With Quote
  #6 (permalink)  
Old 07-11-2020, 08:51 PM
ERA 626's Avatar
CC Member
Visit my Photo Gallery

 
Join Date: Sep 2001
Location: Danville, CA
Cobra Make, Engine: CSX 6079 482CI CSX cross ram
Posts: 1,120
Not Ranked     
Default

he should be able to simply bypass the rheostat and touch the 2 wires together and the lights should come on.
Reply With Quote
  #7 (permalink)  
Old 07-11-2020, 09:21 PM
Gaz64's Avatar
CC Member
Visit my Photo Gallery

 
Join Date: May 2008
Location: Brisbane, QLD
Cobra Make, Engine:
Posts: 2,460
Not Ranked     
Default

Quote:
Originally Posted by ERA 626 View Post
he should be able to simply bypass the rheostat and touch the 2 wires together and the lights should come on.
Yes, that would be correct, if the rheostat is the fault.
__________________
Gary

Gold Certified Holden Technician
Reply With Quote
  #8 (permalink)  
Old 07-11-2020, 09:21 PM
767Jockey's Avatar
Senior Club Cobra Member
Visit my Photo Gallery

 
Join Date: Feb 2005
Cobra Make, Engine: Contemporary, FE, Tremec TKO 600
Posts: 1,676
Not Ranked     
Default

Quote:
Originally Posted by ERA 626 View Post
he should be able to simply bypass the rheostat and touch the 2 wires together and the lights should come on.
Thanks what I was thinking, quick and easy. I don't even have to remove the rheostat from the dash to do it. In fact I'm thinking I don't even have to remove the wires from the rheostat to do it, just connect a jumper between the two wires on the back, that should bypass the switch and the lights should come on if the circuit is good. No?
Reply With Quote
  #9 (permalink)  
Old 07-11-2020, 09:28 PM
Gaz64's Avatar
CC Member
Visit my Photo Gallery

 
Join Date: May 2008
Location: Brisbane, QLD
Cobra Make, Engine:
Posts: 2,460
Not Ranked     
Default

Quote:
Originally Posted by 767Jockey View Post
Thanks what I was thinking, quick and easy. I don't even have to remove the rheostat from the dash to do it. In fact I'm thinking I don't even have to remove the wires from the rheostat to do it, just connect a jumper between the two wires on the back, that should bypass the switch and the lights should come on if the circuit is good. No?
Yes, just a jumper in parallel will bypass the rheostat, 0 ohms (jumper) in parallel with example 50 ohms (rheostat) equals 0 ohms. Lights should be full bright if rheostat is faulty.
__________________
Gary

Gold Certified Holden Technician

Last edited by Gaz64; 07-12-2020 at 07:37 PM..
Reply With Quote
  #10 (permalink)  
Old 07-12-2020, 01:42 PM
Blas's Avatar
CC Member
Visit my Photo Gallery

 
Join Date: Sep 2002
Cobra Make, Engine: SPF#0760
Posts: 3,149
Not Ranked     
Default

If your dash lights are dim, I suggest removing the dimmer completely. The dash bulbs never get a full 12v even with the dimmer full on. Feel free to PM me if you have questions.
Blas
__________________
Wiring Diagrams: SPF MKII, MKIII, GT40, CSX7000, CSX8000, and Shelby Sebring & Bondurant Tribute Cars.
Owner’s Manuals: SPF MKII, CSX7000, CSX8000, Sebring, Bondurant, & Cinema Tribute Cars.

Large, easy to read and trace schematics with part numbers, wire colors, wire gauge, fuses, and electrical upgrade information. Trouble-shooting and replacement part numbers for those roadside repair adventures.
SPFWiringDiagrams@Comcast.net
Reply With Quote
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
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -7. The time now is 07:41 AM.


Powered by vBulletin® Version 3.8.0
Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.
Search Engine Friendly URLs by vBSEO 3.6.0
The representations expressed are the representations and opinions of the clubcobra.com forum members and do not necessarily reflect the opinions and viewpoints of the site owners, moderators, Shelby American, any other replica manufacturer, Ford Motor Company. This website has been planned and developed by clubcobra.com and its forum members and should not be construed as being endorsed by Ford Motor Company, or Shelby American or any other manufacturer unless expressly noted by that entity. "Cobra" and the Cobra logo are registered trademarks for Ford Motor Co., Inc. clubcobra.com forum members agree not to post any copyrighted material unless the copyrighted material is owned by you. Although we do not and cannot review the messages posted and are not responsible for the content of any of these messages, we reserve the right to delete any message for any reason whatsoever. You remain solely responsible for the content of your messages, and you agree to indemnify and hold us harmless with respect to any claim based upon transmission of your message(s). Thank you for visiting clubcobra.com. For full policy documentation refer to the following link: CC Policy
Links monetized by VigLink