Battery Light

[Joel]

I've seperated the Sierra instrument cluster loom to provide feeds for all new gauges/switches/lights. The good news is that everything is now working except one last thing. The blue wire for the battery warning light wasn't in the loom. The cut off end was in the connector, but no wire in sight. It must have been removed for some reason by a previous owner.

 

Anyway, I've put in a new wire but it feeds directly from the dash light to the alternator, so not surprisingly the light is on all the time. If I understand the Haynes manual right, there should be a diode in the line, but I don't know where to find it to incorporate it into my new setup.

 

So is it possible to fit an in-line diode, like an in-line fuse, and if so where do I get it from and what do I ask for? I presume they come in different sizes, strengths etc.

[Guest Taffy Rob]

Hi Joel,

um, Im not sure how a diode will make a lot of difference? The alternator supplies dc voltage at varying levels all the time it is turning, so I dont quite see how it would work.

But I will have a go...

I would reckon you need a wire running from the battery to the alternator (which must exist in some form already - sorry but auto electrics are not my strong point), and fit two diodes in line onto this, pointing in the direction that will allow current to flow from battery to alternator but not vice-versa. I expect some kind of inline arrangement is easily come by. The switching voltage is not crucial, most come in at .7 which will do fine, make sure it can take 16 volts and a highish level of current - if you go somewhere like Maplins they will advise. Take a feed to the bulb from between the two diodes. Now, I expect anyone with a bit of knowledge will scoff at this, but it should work.

When you are starting, or have the ignition on, the circuit is powered, and current gets to the light. When the alternator is up and running, and starts charging the car, then the voltage coming from it is in excess of the supply from the battery, so the diodes 'turn off', meaning no supply to the bulb. Should work in theory....

[Longboarder]

Check that you have the circuit right for the ign light. One contact on the light has an ignition live supply and the other contact connects to terminal 61 on the alternator. No earth! All model years have direct connections and no diode except 87-89 and even then it is shown with or without. I think if you have the circuit right it should work unless 61 on the alternator is not kicking out 12 volts.

 

Nigel

[Joel]

Problem Solved.

 

Double checked my connections and found I had misaken the blue wire at the coil for a blue/white wire, which I think goes to the auto choke.

 

2 minutes to fix, and now it's working fine.

 

Thus concludes my dashboard wiring