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 Posted: 06-23-2024 06:24 pm
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vnavaret
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Lads:

I have a 1974 that I am in the process of restoring, as some of you have read.

I have repaired my wire harness with new connectors, rewrapped, etc and have been routing and connecting the wires as I assemble the car.

The 1974 year was "blessed" by our benevolent congress with an ignition interlock that prevents starting if the seat belt is not fastened. May the fleas of a thousand camels infest the armpits of every congressman and congresswoman for this idiotic idea.

I need to rewire the relay that controls this, for the sake of originality (I am anal retentive about this sort of thing). My wonderful JHPS wiring diagram does not show the relay, although it does show the wiring for the seat belt and occupant switches. <sigh>

Anyone have of list of wire colors and pin outs, or a diagram for this contraption?

Thanks,

Vance

Last edited on 06-23-2024 06:25 pm by vnavaret

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 Posted: 06-24-2024 02:37 pm
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noomg
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Vance,

"For the sake of originality", you're not actually going to try to reactivate the seat belt interlock system are you? If so it'll require two muffin switches that fit in the seat bottoms. In most cars those are long gone, I have one intact the other was at some point clipped and removed. Back then disabling these systems was almost a sport, some clipped the wires, some pulled the switches out, but the most popular fix was clipping in the seat belts behind the seats.

If you just want to bypass the interlock system like most guys have done it's easy. The control box has 12 terminals in a circle you just need a jumper wire to connect two terminals which effectively bypasses the interlock. It's been a while so I don't recall which two terminals they are I think it was #9 and #11 but I'm not sure, hopefully someone who knows will chime in with the correct numbers.

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 Posted: 06-24-2024 03:19 pm
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vnavaret
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noomg wrote: Vance,

"For the sake of originality", you're not actually going to try to reactivate the seat belt interlock system are you? If so it'll require two muffin switches that fit in the seat bottoms.
Heavens, no. It is a PITA.

But I do want the wiring to be correct. I had the same system in my 1974 Triumph TR6, at least I think it was probably the same system. Disabling it was simply a matter of unplugging the wire harness from the seat switches. The default mode was to allow the car to start if no one was sitting in the seat. Disconnect the seat switch and voila! It was a regular car, and if for some unlikely reason someone wanted to enable the system, just plug the seat switch back into the harness.

The previous owner of the car hacked into the wiring harness, and cut a couple of wires, then ran his own wire from the ignition switch off to the starter solenoid.

I can get some used seat switches and yes, the originals are long gone. Before you say "Vance was an abused child, that is why he loves to suffer in this way" I must state for the record that I enjoy the challenge of getting things back to their original state - finding parts, documentation, etc is a challenge I enjoy. If I didn't like doing the research and looking in obscure places for parts, I would be driving a new MX-5 Miata instead of restoring a car that very few people have ever heard of, much less seen in the flesh.

Besides, driving an old car with minimal pollution controls is very pleasing, because I am figuratively sticking my thumb in the eye of that little twerp Greta Thornberg. =:-o

Vance

Last edited on 06-24-2024 03:24 pm by vnavaret

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 Posted: 06-24-2024 07:02 pm
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noomg
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Vance,

One of the things that appealed to me when I was considering getting a J/H was to pass smog test the motor required no smog equipment; no cat, no EGR valve, no air pump, almost nothing which means it's a very efficient mill.

My experience with a seat belt interlock was my brand new '75 VW Scirocco, I didn't notice it because I always wore my seat belt until one day I set a bag of groceries on the passenger seat, the car wouldn't start until I belted the groceries in.

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 Posted: 06-26-2024 01:54 am
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vnavaret
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noomg wrote: Vance,
one day I set a bag of groceries on the passenger seat, the car wouldn't start until I belted the groceries in.

Hey! Groceries care about safety too!

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 Posted: 06-26-2024 02:51 pm
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noomg
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Vance,

Yes the seventies was truly "The Golden Age of Shoddy Workmanship", you need look no further than the last MGBs.

Getting back to your original question there are three electrical schematic wiring diagrams that I know of. Delta sells two, late '74 and early '73 model diagrams and one ('74 models) that came with the Owners Manual, I'd recommend getting all three. The two '74 W/Ds show the seat belt interlock control box, I'd guess the '73s didn't have them. The Owners Manual W/D version is easiest to follow when tracking what runs to the control box. When I installed my new wiring harness I cross referenced all three and they were all helpful.

Your thread got me thinking when I got the car while it was beat up inside and out mechanically everything worked fine and there was no modification to the control box (jumper) but after I replaced the W/H it was necessary to jump the terminals. I don't know why this was but as far as I can tell all the PO did was cut the seat switches. Maybe that's all you'll need to do.

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 Posted: 06-28-2024 03:04 pm
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redracer
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Vance, noomg: this has been written up many times years ago, so nothing new. The circular 12 pin logic connection should be #11 and #12. Short these 2 out--no more problems

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 Posted: 06-30-2024 07:19 pm
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vnavaret
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Folks:
After some searching on the web, I found some guidance on the wiring of the JH in a very unlikely place, flickr.com.

There are very detailed high-res photos of the restoration of a JH. A couple of them actually, located here:  JH Resto.

The pictures are super sharp, and lo and behold show electrical connections in good detail. I have printed out several of the photos to aid in positioning the wiring harness and a couple of the more mysterious connections.

This site has restos on several different cars, but if you explore all of the pages with photos, you will see how Mr. McPheat (the poster's name) did a lot of stuff. It is fun just to see the various cars he has restored.

I am sure that this link will expire some day, as have many of the links on this site, so if any of the photos are of use, you should copy them. When you down load them, you are offered a choice of the resolution you want, I always took the highest resolution.

I have attached one of the photos to show you what I mean. This is one of the lowest resolutions offered.

Vance

Attachment: 49830751233_19649429f8_w.jpg (Downloaded 14 times)

Last edited on 06-30-2024 07:21 pm by vnavaret

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