Seatbelt Warning Light Relay Circuit - Canadian Mustang Owners Club - Ford Mustang Forums

D.I.Y. Articles Have an article to help other Mustang owners? Post it here.

LinkBack Thread Tools
Old 06-03-2018, 07:41 AM   #1  
CMOC Newbie
Thread Starter
RoddinRob's Avatar
Join Date: Dec 2017
Location: Sudbury
Posts: 10
Seatbelt Warning Light Relay Circuit

I was getting the safety check done on my 67 fastback & found out that the seatbelt warning light needs to work properly. Mine was staying on. SO - I started searching for replacement options... All cost prohibitive. Being an old-school electronics guy, I built a replacement with a 555 timer, a few resistors & capacitor. I changed the lamp to an LED, so that I didn't need an interposing relay. I'm attaching a couple of links: First one is for the circuit I built, the second is for calculating the time constant (how long before the light goes out) You put in the values of the components & the voltage & it will calculate the time for you. You can play with the component values to get the delay you want. I used a 330uf capacitor & a 20k-ohm resistor at 12.7 volts to get a time of 6.6 seconds. I figure that's long enough. On the circuit diagram from the link, the values are different. HOWEVER - the 470 ohm resistor is there to limit the current through the LED, so you don't play with that one or you can burn-out the LED quickly. I had all this stuff lying around, so it didn't cost me anything, but if you have o buy the stuff from an electronics store, you could build it for like $20 & it will last forever. Also attaching a pic of the unit I built. There are 2 OE styles for these cars - one round, the other rectangular. They mount under the dash on the firewall between the fuse block & brake pedal, so unless you're looking for 'concours correct', no one is going to see it.


How to Build a Delay Before Turn Off Circuit with a 555 Timer
Attached Thumbnails
Seatbelt Warning Light Relay Circuit-2018-06-02-14.33.26.jpg  
RoddinRob is offline   Reply With Quote

Related Topics
Thread Thread Starter Forum Replies Last Post
Video: Watch the #61 Roush Mustang Boss 302R lap Austinís Circuit of the Americas VAEM Ford Mustang Pictures and Videos 8 03-04-2013 10:32 PM
help....wheres the fuel pump relay? tear u a new 1 5.0L 12 11-21-2005 10:13 AM

Thread Tools

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 Off
Pingbacks are Off
Refbacks are Off

All times are GMT -5. The time now is 08:56 AM.

© 2018 MH Sub I, LLC dba Internet Brands
We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to and affiliated sites.