"Fasten Belts" light and buzzer turning on randomly

[grazapin]

In the past couple weeks the "Fasten Belts" light and buzzer have started acting up in my '75 B210. I first noticed it when it was parked and not running when I heard that familiar buzzer sound faintly while I walked by my car in the driveway, and on looking inside I saw the "Fasten Belts" light was on. It will randomly turn on and off while parked and I sometimes hear the relay clicking when I'm driving as well.

 

It seems like when it's functioning normally the condition necessary to trigger the "Fasten Belts" warning is for the key to be turned to on when the seatbelt is not fastened, so I'm hoping since I hear the relay clicking while the belt is fastened that the relay is going bad. Either that or I have sporadic feedback from the ignition switch or seatbelt sensor.

 

Does anyone know which relay I'd need to replace and where exactly it is? Also, which part number would it be? The wiring diagram in my Clymer manual shows the relays but doesn't have part numbers. Rockauto lists 10 different models of multi-function relays for my car. I'm starting to think I should just bite the bullet and pay for a factory service manual.

[Middle man]

When I first bought my 80 datsun,I went through the wiring under the dash. I had other issues and wanted to do a visual on fuses and disconnected or worn elect. parts. I noticed a white plastic connector disconnected behind gauges on driver side. Plugged it together and now the buzzer works and shuts off after 3 beeps. The p.o. did not like it and unplugged it.So...unless its really important you could just pull the plug. I always wear my belt so I really don't care either way.It scared the hell out of me when it first went off,thought I f/ed something up.

[datzenmike]

It shouldn't be on with the ignition OFF. Key has to be on to power the relay. A bad relay can't run on no power.

[grazapin]

So it's more likely an ignition switch issue?

[datzenmike]

Let's just say... could be. The seat belt buzzer is on a fuse.

 

If you can find that fuse and pull it and the buzzing keeps going then power isn't coming from the ignition. This would indicate power coming from somewhere else and getting onto the power wire to the seat belt warning system. Possibly some other accessory run on the same fuse.

 

If the buzzing stops then power IS coming from the fuse and from the ignition side at least.

[grazapin]

I'll check the fuse.

 

It could be a short caused by water. Since the rain hasn't been as intense the past few days I haven't noticed it happening.