Seat Belt interlock problem

[Robert S.]

Re: Seat Belt interlock problem

The interlock system is reasonably smart (INTENDED to prevent the car from starting IF appropriate safety pre-conditions weren't met). What makes you think that disconnecting the seat weight sensor and belt employed sensor (under the seat) is going to make the interlock system 'happy' and allow the engine to start?

Removing external inputs from a computer generally doesn't stop it from running...

Jack-
Interlock only (previously) worked when I connected the seat connectors. when I unplugged them again interlock was inoperative for six months until two days ago that is. I just want to start the car.

[Robert S.]

Re: Seat Belt interlock problem

Wiring print for MT application attached. Note that the first thing to do is to check all functions without the SBI system involved. The SBI is simply an overlay over the standard system If the relay button does not allow a start, then check out the conventional starting system first! That includes the clutch switch and all Grounds! If you can't read this print, email me and I'll send you a larger size file.

Bill-
The clutch switch is on the pedal? Neutral start/back up lights are out but they've been out with the interlock not operating and car was able to start since I bought it in January.

[Robert S.]

Re: Seat Belt interlock problem

There is more than 1 relay in the system,the relay I speak of is an emergency bypass relay for 1 start at a time,this relay will not cause the car not to start it is there only to start your car if another part of the system fails.
If you want push the button and try a 1 time start,if it starts that rules out the safety switch and solenoid.

Roger-
1997426 seat belt starter interlock control. Could this be causing problem if defective? I bought this ($17. GM nos) on ebay just in case.

[William C.]

Re: Seat Belt interlock problem

The point is, I really believe the interlock is NOT your problem. You need to be verifying the starting system, especially the ground paths.

[Roger O.]

Re: Seat Belt interlock problem

The point is, I really believe the interlock is NOT your problem. You need to be verifying the starting system, especially the ground paths.

Thats why I'm suggesting the jumper,the jumper will bypass the interlock system and we can test this car like a 73 and earlier. Once the jumper is in place there will be 2 very good possibilities , the clutch switch and the starter solenoid.

[Roger O.]

Re: Seat Belt interlock problem

Roger-
1997426 seat belt starter interlock control. Could this be causing problem if defective? I bought this ($17. GM nos) on ebay just in case.

Its possible (that relay is the one inside the car) but before we start throwing parts at it lets try the jumper or the 1 time push button start.

Robert I think you said you tried the push button and you said it didn't work.
To be honest I don't remember ever using the button to start. The directions would be in the owners manual but if I had to guess I would say you #1 turn ignition to ON #2 push button on silver relay switch #3 turn ignition to start "directly" from ON position ( do not rotate to off then to start) (clutch in of course).

[Michael W.]

Re: Seat Belt interlock problem

.....and the neutral safety swtch (backup lights not working) I think the switch is part of the backup light operation.

A 4 speed car does not have a neutral safety switch, automatics only. The backup light switch has no connection to the start circuit.

[William C.]

Re: Seat Belt interlock problem

I believe they are really meaning the clutch switch which requires the clutch to be depressed to start a manual trans car.

[Robert S.]

Re: Seat Belt interlock problem

Oh... it starts without clutch pedal depressed

[Robert S.]

Re: Seat Belt interlock problem

Roger-
Car starts with jumper!!...seat belt buzzer/light stays on after started.
By the way, I had mentioned car starts without clutch depressed and backup lights out (since I bought it in January) You mentioned clutch switch is a possible cause or possibly a piece fell off it?

[Roger O.]

Re: Seat Belt interlock problem

Roger-
Car starts with jumper!!...seat belt buzzer/light stays on after started.
By the way, I had mentioned car starts without clutch depressed and backup lights out (since I bought it in January) You mentioned clutch switch is a possible cause or possibly a piece fell off it?

Great glad you got it started.

I was saying if the 2 wire connector fell off the clutch safety switch that would explain your "no start" condition.

Since it starts with the jumper and the clutch NOT depressed I would say the clutch safety switch has been wired around.

At this point buying the 1997426 relay might have been a good thing. Its very possible that is what failed.

I would unplug the old 1997426 and see if the buzzer stops, if not the buzzer should be very close in the console.

Sounds like plugging the clutch switch back in , replacing the 1997426 and a new button relay switch in the engine compartment might have you back in business if you want the interlock to work.
Keep your jumper wire in case you need to use it again in the future.

[Roger O.]

Re: Seat Belt interlock problem

Roger-
Car starts with jumper!!...seat belt buzzer/light stays on after started.
By the way, I had mentioned car starts without clutch depressed and backup lights out (since I bought it in January) You mentioned clutch switch is a possible cause or possibly a piece fell off it?

Back up lights..
I would say to check the backup light fuse but you didn't mention your turn signals not working and they are on the same fuse so the fuse is good.
Your 4 speed car has a separate switch down at the transmission that controls the backup lights.
Since the one jumper worked I can explain how to jumper the backup lights to try and diagnose them if you like.

NOTE- An automatic car has the neutral safety switch AND backup light switch all-in-one mounted inside the car on the side of the shifter.

[Robert S.]

Re: Seat Belt interlock problem

disconnected buzzer/light at the console.

[John H.]

Re: Seat Belt interlock problem

Oh... it starts without clutch pedal depressed

Bob -

Photo below is from a '69 Camaro, but the clutch safety switch design was essentially the same across Chevrolet car lines; the switch is on the outboard side of the pedal support, operated by a wire rod from a hole in the clutch pedal. There are two purple wires on the switch; with the clutch pedal depressed, the switch is closed, and when the clutch pedal is up against the rubber bumper, the switch is open. The switch is in series with the purple "start" wire that goes from the ignition switch on top of the steering column to the "S" terminal on the starter solenoid, which energizes the starter. The installation is shown in UPC 6 in your Assembly Manual.

[Roger O.]

Re: Seat Belt interlock problem

Robert just so you don't get confused on your 74 the clutch switch that John posted above will have 1 purple/white and 1 green/black , the wiring colors changed with the interlock system.