Those of us lucky enough to have a 1974 vehicle have learned to work with or around the seatbelt interlock system. Since I'm going through some electrical updates in my '74, I'd like to completely remove it from the harness and the system. Get rid of the belt and seat sensors, the by-pass relay, the control modules and all related wiring. I assume it would be a case of removing it all and making sure the neutral safety for autos or clutch switch for manuals is performing their function instead of the belt interlock.

Any one out there done this? Can you confirm its that straight forward or not, advice on potential gotchas, or suggestion to make it go smoothly?

Actually if you concern is about the interlock system itself but not the buzzer warning systems, you could reach these three options:

1-Get the orange module used in Canada, which is a non interlocked control unit juts a sensors control box to still keep working the warning signals. Latelly they have floated around on $20-50 on ebay

2- jump out both yellow wires on reset button plug. No need to cut anything, just install a jumper wire between both yellow wires and even still plug the harness to the reset button.

3-you can also swap around both yellow wires on engine harness. This will send the straigh signal from ign switch to starter relay, instead reach the interlock box.

I have covered this extensivelly on FBBO and 3rd gen charger board, pics and diagrams included.

You could also get a 71 underdash harness for your 74 and match engine bay harness wires with it ( several wires were swaped around all allong the 71/74 production ). On 71 harness just will need to replace the terminals to the door jam switch and swap the wipers plug. Wires are the same between all 71/74, just 71s got diff prongs disposition ( 71 uses in fact 2 plugs for wiper switch instead one piece plug ). The advantage on use the 71 harness is it doesn't get any sensor or buzzer setup. No cut anything and no extra plugs hanging around or running to kick panel area for sensors, but just the optional light on warning buzzer. Seatbelt light works with courtesy ign light via time delay flasher/relay

then you can also unwrapp the underdash harness and remove all the wiring related to interlock system. Will need still to swap around the yellow wires on bulkhead/engine bay side... Being there done that., Once, when I still didn't have completed the interlock system to my 74 assembled in Vzla ( 74s in Vzla were wired just like 71s by the local assembly plant since interlock system wasn't a local requirement), I got a 74 harness what I modified to use on my car thinking on next upgrade. Once got it completed reisntalled everything back... yes I like all warning buzzers and interlock system working.

about the safety ground for starter relay. Even the interlock system gets that signal, it makes NOTHING to the ground safety system to the starter relay really. Interlock system just uses this signal to know when the car is geared or not to buzz/light on the seatbelt warning system, without interact with starter relay. Starter relay gets blocked just to the IGN yellow wire network.

This is the last thread talked about that on FBBO

https://www.forbbodiesonly.com/moparforum/threads/74-charger-identify-this-part.167504/

several cheap orange boxes on ebay:

https://www.ebay.com/sch/i.html?_fr...leDesc=0&_osacat=0&_odkw=3501371

using the orange box, you can remove the reset button pigtail if you want from engine harness to clean up the engine bay, Since being the yewllow wire already jumpet at control box, the reset button won't get any function anymore

Thanks Nacho, I'll go check out your other thread.

The goal is to get rid of it all, not just silence it or work around it. Originally wanted to completely replace the harness, but have decided that may be for a later date.

Well, everything will depend on how clean you want to make the work!

True. My biggest concern at the moment is having it partially removed yet still being functional. Because of a seat change, the seat and belt wiring is gone. Because of a change up in ignition and accessories, the underhood portion was easily removed. However, the dash portion and relay box remain. I don't want ti impede the ability to start the engine because the relay remains. Can it simply be unplugged or do I need an orange box to make it work until the balance of the in dash system can be removed?

Because this issue wasn't challenging enough, I also have a new engine that needs to be run in, so I can't spend hours experimenting with trying to turn over the system to check functionality while the engine bumps over partial revolutions without firing.

Just jump out the yellow wires on reset button if wires/plug are still there hanging around, or jump yellow wires at control box plug ( you'll find two yellow wires one of them traced black ) down the dash frame removing the box... or swap around both yellow wires at engine harness plug end running to bulkhead. You can make a cleaner job later when decide to remove the harness and work it out of the car.

You'll loose of course the key in buzzer and lights on buzzer ( if optioned ) when removing the control box. No need to remove it thought.

When making a cleaner job removing everything, will need to make the wiring for key in and lights on buzzer if you want or care about them. Aside get the buzzers for them. ( key in buzzer is the same horn relay on 71/73 )

I guess in fact if you are installing an aftermarket ignition system you already are hacking up the engine harness, so simply cut the harness section running to reset button and splice together both yellow wires. Isolate the blue one ( which comes from Run circuit ) and the black wire there is a ground wire attached as far I recall to one of the wiper motor mounting studs. You should be able to pull it out and should leave the wrapped harness easily or maybe use that wire to give some ground to something around ( same to the blue wire coming from Run circuit ). At your wish.

Oh yea, I've got some changes . Two field alternator swapped to single wire system, 5 pin to 4 in ECU, 4 post to 2 post ballast, elimination of all trouble light sensors to mechanical gauges, methanol injection system, Omni Magnum sensing coil instead of stock oil filled, auto to 4 speed, elimination of amp gauge, eliminated factory a/c, rear mounted battery, ignition/battery cut off switch. The wiring is seeing a lot of changes. Only untouched section of the engine harness is the wiper motor and front light harness. The lug with all the start/run/alt/interlock mechanism is basically being gutted

Maybe I just leave that harness intact to start and run in the engine, then yank it apart when I'm not worried about wiping all the assembly lube out of the engine by playing with the start and run systems. Of course with the seat change, the seat wires and the seat belt wires are already long gone.

just splice together both yellow wires originally reaching the reset interlock button and you are done.

hi,
if you can find it there is a factory TSB from Chrysler about disabling system, if I remember correctly you just had to solder a spot on control box printed circuit, 40 years ago
Gary

Retro fitted 2 74 cars,a Charger and a Challenger.
Both had baked electrical systems and it was easier to install a complete used 72 or 73 dash and underhood harnesses .
I do continuity tests on all circuits,repair any wiries as needed and retro fit an electronic ignition harness if i use a 72 harness. Also good time to clean all of the spades in the bulkhead connector
I re-wrap the harnesses for a clean appearance.
I always bypass the ammeter gauge at the same time.
I did not bother plugging in the relays for the buzzers and left the seat sensors alone--nobody sees them anyways.
Hope this helps

My override switch works fine, but I did do the yellow wire bypass that nacho speaks about prior so I never have to deal with it.

The original harness is pretty fragged, but I've plugged it all back in to get the engine through its run in. Then I'll deal with harness modifications, although the more I look at it, I think a complete aftermarket replacement with additional circuits may be the better route to go, even though the price tag is a bit steep.

making that, it won't matter anymore what you still have or not on car of the interlock system. Just that removing the control box will loose the rest of warning systems too ( key in &/or lights on if optioned )

the lights on option is just a matter of buzzer replacement.

this:




for this:



car is ready for the 4 prongs one, but when lights on buzzer was not optioned, the two prongs one was the one installed on same plug ( just two cavities on plug going anywhere )