Maymyvetteliveforevr

Patro46
Thank you for the suggestion, I would however like to find the problem first before I begin to modify.

lionelhutz
Sounds good and that's what I would like to do.

Sigforty
Correct, there isn't enough power or ground to light up the stock bulb. I'm assuming this problem occurred during the 27 years in storage as I don't remember it lighting up when I put it back on the road after the restoration I did.

The red led bulb stays dim regardless of whether the ignition is on/off, seatbelt on/off, sitting in the seat or not. The only change is to the led bulb which gets slightly dimmer when I buckle up the seatbelt with an empty seat.

Is the seatbelt relay located behind the passenger seat where the spare tire jack is located? I believe it's a 3 prong relay, if so how do I test it, or can I override it for diagnostic purposes?

I don't remember the car having a seat belt warning buzzer, but then I can't remember that far back. Where is that located?

Sigforty

I am not sure on the location of any of the components as my 71 does not have the same setup. Do you have an AIM or service manual? Those should give you the locations of the parts. I believe there may be one or two items for the buzzer and probably the same for the relays. I think the later systems had a timed relay that is probably the source of your issues.

Peterbuilt

Do you have a box like this under the hood and on the right firewall?

Is your 75 a stick or automatic?

Maymyvetteliveforevr

Sigforty
Yes I have the 75 AIM but I lent it out couple weeks ago.

Peterbuilt

Yes, I do and it's had a cover on it since I bought it new in 75. There was never a relay installed in it and I never had to put on the seat belts in order to start the car. This is a Canadian Car is that matters.

It's an automatic.

Below are photos during my restoration, you can see the clear plastic cap.

DUB

I honestly do not know if it was an 'export' model if that seat belt warning system is the same as here in the US or not. I am sure it is. BUT..I do know I have had one customer that had an 'export' 1978 Corvette that on the speedometer....INSTEAD of MPH being the prominent scale..it was actually Kilometers.....THUS ...his odometer reading was in Kilometers and NOT miles. He had a major hassle with the DMV.

I am assuming that you are wanting the seat belt warning system to work as designed???

DUB

Peterbuilt

Okay, lets say you don't have the seat belt interlock system, that's good.

The pressure switches (one under each seat) is normally open (OFF) until someone sits in the seat.
The switches in the buckles are normally closed (ON) until you buckle up which opens the circuit.
Do they work properly?

The neutral safety switch keeps the seat belt light OFF until you shift out of PARK.
Once you shift into D the light will go ON until you buckle up.
Does it work that way on your car?

Maymyvetteliveforevr

DUB
yes, I want the seat belt system to operate and having an led bulb on dim all the time is a problem for me.

Peterbuilt
I just removed the passenger seat as I needed to do some work in the rear compartment and I didn't disconnect any harness so I don't think there is one on the passenger seat. I did see a wire from the seat belt buckle to the center console.

If I buckle up the seat belt on the passenger side (empty seat) the led bulb goes even dimmer.

I will check the operation of the safety neutral switch in relation to the seat belt light tomorrow.

For the sake of diagnostics, I wonder if I should be doing all tests with the oem bulb or led bulb?

69Vett

dissconnect seat belt switch, if dim led goes away, you have dirty seat switch contacts.

Maymyvetteliveforevr

Thanks for the reply 69vette, I disconnected both seat belt wiring from the center console and there was no change.

Antz81

Since he has the base for the relay, which is where the bypass would have been fitted, and it's an export car; i wouldn't be surprised if it has the interlock system, but it had been bypassed with the cover (or under it) at the factory or at the dealership before he took possession.

Peterbuilt

Good question.
Did GM do the bypass before export or did a PO do it and by mistake tie the pink in with the green/black and purple?



Maymy,
Do you have the interlock relay under the console?

Maymyvetteliveforevr

Thanks for the replies.

Antz81 I took possession of the car Jan, 3 1975 from the dealership and it never had a relay in the harness on the firewall. Also it has a plastic cover which also tells me there was never a relay. Also, the relay prevents the car from starting before seat belts are buckled up? If so that's not my problem, as the car starts without seat belts attatched.

PeterbuiltSince I'm the original owner, there was no previous owner.

Antz81

the interlock system also controls the seatbelt warning light. Which is why it's important to know if the rest of the system is there. It seems like it could be since you have the wiring into the engine bay where the relay normally be.

Peterbuilt

Hi again Maymy,
Congratulations on owning your Corvette from new.
I'm sure that it has given you many years of enjoyment.

My 74 service manual only has information showing how to troubleshoot the interlock system.
The internet 75 schematic is not very helpful for your problem.
https://docs.google.com/viewer?a=v&p...WRiNTdjNjdkNTQ

you might find the answer in your 75 service manual or with any luck the people like Dub, Willcox or Richard will see your post and help.

Regards,
Pete.

Maymyvetteliveforevr

Thanks again for the replies.

Antz81Seems all the wiring is there.

PeterbuiltI had the car stored in the garage for 25 years, I'm wondering is there is a bad contact somewhere in the seatbelt system.

I have a copy of that wiring diagram but can't figure out how get it to help me diagnose.

I don' t have a copy of the Factory Service Manual.

Antz81

i don't time to find it right now, but Willcox has a diagram for the '75 that does show the wiring for the interlock system.

Maymyvetteliveforevr

An electrician friend came over today and grounded a harness behind the passenger side dash and the seat belt light is now bright with the stock bulb in it. Not sure what the hell he did or whether that solves the problem but it's on and bright.

Just so I understand, when is the seat belt light supposed to be on?

When you turn on the ignition should the light be on for a times period of time before the seat belts are attached. Does it go off when the car is started. Does the passenger side affect the light in any way.

Can someone tell me the sequence of how the seat belt light works.

Peterbuilt

A new ground for the gauge cluster can fixed the problem!
That's good, but very interesting since the cluster is grounded from the center (black) wire to the water temp gauge.
Maybe you lost that ground when you changed the bulbs.

Seat Belt sequence!
I can't help you on that one as my 74 is different than your year,
Check out your owners manual.

Maymyvetteliveforevr

Peterbuilt

Thanks for the reply, I'm trying to find the proper "Seat Belt" light procedure to continue with the diagnostics as the light works, but I can't seem to turn it off now.

Antz81

I'm not 100% on this, but, it should come on for a few seconds when starting the car, and the if the seat belts are buckled then it should go out again. Earlier vettes like yours also had a should have had sensors in the seats so only the belts only needed to be buckled while someone was sitting in them.
If it won't go out at all try buckling both belts up, or unplugging the wires to the buckles and see what happens.