 Seat Belt Interlock Relay, Late 74-76’ - how does it work? |
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| Superhawk996 |
 May 15 2025, 09:57 AM
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914 Guru  Group: Members Posts: 7,090 Joined: 25-August 18 From: Woods of N. Idaho Member No.: 22,428 Region Association: Galt's Gulch 
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For those of you that despise the seatbelt / starter interlock and the horrific screeching noise the seat belt buzzer makes - let me say I understand completely. As I’ve been playing with this on the bench my wife now hates the noise just as much as I do.
This thread is going to explain how it works and how to bench test it over the coming days.  Credit is owed to @JeffBowlsby , @Bdstone914 , and @Montreal914 for providing me with donor parts that will make this thread possible. Eventually I will post the schematic of this ridiculous conglomeration of components. I hope to eventually put the circuit in LTSpice to help verify its theoretical operation. I make no warranty as to the accuracy of the schematic - this is just me satisfying my own curiosity.  If you have no interest in my personality defects that would lead me to take on this little project; ignore this thread. If you have a late car with an in-op system and eventually want to get it working - this thread is for you. Toward the end I’ll share some ideas on how to get rid of or to change that horrific buzzer noise. |
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| rjames |
May 15 2025, 06:01 PM
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#2
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I'm made of metal Group: Members Posts: 4,259 Joined: 24-July 05 From: Shoreline, WA Member No.: 4,467 Region Association: Pacific Northwest
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F that buzzer. (IMG:style_emoticons/default/laugh.gif)
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| Superhawk996 |
May 15 2025, 06:38 PM
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#3
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914 Guru Group: Members Posts: 7,090 Joined: 25-August 18 From: Woods of N. Idaho Member No.: 22,428 Region Association: Galt's Gulch
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QUOTE(rjames @ May 15 2025, 08:01 PM)  (IMG:style_emoticons/default/lol-2.gif) for sure! I’ll have solutions for this later More stuff coming. I don’t have time to post it all in one giant chunk. Tomorrow I’ll cover the seat cushion and door switch behaviors. (IMG:style_emoticons/default/laugh.gif) |
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Posts in this topic
Superhawk996 Seat Belt Interlock Relay May 15 2025, 09:57 AM
Superhawk996 My curiosity in this part is the result of the Hay... May 15 2025, 10:05 AM Superhawk996 Let’s start with how this thing is supposed to w... May 15 2025, 10:06 AM ClayPerrine While I am curious to know how it works, I am stil... May 15 2025, 11:09 AM
Superhawk996
While I am curious to know how it works, I am sti... May 15 2025, 11:34 AM 914werke [url=http://www.914world.com/bbs2/index.php?s=... May 15 2025, 11:44 AM Superhawk996
[url=http://www.914world.com/bbs2/index.php?s=... May 15 2025, 11:59 AM Superhawk996 So this is where things start to go astray.
I ca... May 15 2025, 11:57 AM fiacra
The one thing I haven’t been able to find is a... May 15 2025, 04:51 PM Superhawk996
Here you go. From my 1975 Owner's manual. ... May 15 2025, 06:52 PM rjames Following
:popcorn:
I've thought about tryi... May 15 2025, 12:53 PM Root_Werks
Following
:popcorn:
I've thought about try... May 15 2025, 01:06 PM Superhawk996 Let’s start with the Haynes / factory manual bla... May 15 2025, 02:47 PM Superhawk996 The PIN ID’s are clearly labeled on the interloc... May 15 2025, 02:59 PM Superhawk996 The Fasten Seat Belt light is powered by 12v suppl... May 15 2025, 03:03 PM Superhawk996 So let’s talk about the horrific buzzer
If a s... May 15 2025, 03:39 PM Artfrombama Interesting, appreciate the research!
P. O. di... May 15 2025, 07:05 PM JeffBowlsby This is awesome Phil! Chipping away at one of... May 15 2025, 09:51 PM StarBear :popcorn: Enjoying this immensely.
Disconnected m... May 16 2025, 06:53 AM flipb Just checked my 1974 manual and it's pretty mu... May 16 2025, 07:08 AM friethmiller Great thread, Phil. :popcorn: On my red '74 ... May 16 2025, 07:30 AM Superhawk996
I know I have the smaller relay (see arrow). N... May 16 2025, 12:54 PM barefoot
I know I have the smaller relay (see arrow). ... May 16 2025, 01:29 PM Superhawk996
You must have a lot of free time on your hands, ... May 16 2025, 02:00 PM ClayPerrine
[quote name='barefoot' post='3205819' date='May 1... May 16 2025, 02:49 PM Superhawk996
I would just build a small electronic circuit wi... May 16 2025, 05:37 PM ClayPerrine I can remember taking the seat cushion out of Bett... May 16 2025, 09:16 AM Superhawk996
I can remember taking the seat cushion out of Bet... May 16 2025, 12:56 PM davep Just saw this thread. I worked on this about 3 yea... May 16 2025, 03:18 PM Superhawk996
The two minute restart delay comes from the oil ... May 16 2025, 05:31 PM Superhawk996 Driver side seat circuits
The driver side seat c... May 16 2025, 07:22 PM Superhawk996 Here’s how the situation looks on the bench with... May 16 2025, 07:32 PM Superhawk996 And again with the seat belt fastened where the op... May 16 2025, 07:34 PM Superhawk996 So at this point we are though the sit down & ... May 16 2025, 08:06 PM Superhawk996 I know almost no one cares about the internal deta... May 16 2025, 08:26 PM Superhawk996 Oh - here’s which relays are which
The starter... May 16 2025, 09:03 PM Superhawk996 More coming on observed anomalies and how the oil ... May 16 2025, 09:07 PM Superhawk996 This video shows behavior of the relay under a cou... May 19 2025, 11:44 AM |
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