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i have an 88 samurai and when its idiling if i rev it... the lights get significantly brighter.. both headlights and instrument lights? i have the stock alternator but it was "beefed up" by a reputable alternator shop and i also have a new optima battery. also my BRAKE light on my gauge cluster is always on??? i have brand new brakes front and rear? and my emergency brake works fine? any ideas why the light is on? the brake fluid should be toped off but i will check that one more time..thanks guys any suggestions are greatly appreciated always...:D
 

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first quick check is charging voltage. with a fully charge battery and engine at 2500 rpm, the voltage at the battery should be between 13.5 to 14.8. if voltage falls outside this range the alt is bad. to check the amp out put of alt, the voltage ripple pattern, and battery condition you will need more test equipment. having a repair facility diagnose the charging system will cost as much as the alt or battery. so just pick one and change it. if you are lucky that will fix problem and if not change the other part. 99.9% of the time it is the alt or battery that fails in charging system
SQUID
 

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mine does exactly the same thing... lights are dim at idle, and once its over about 1500rpm its a fair bit brigher, and highway speeds (~3500rpm @ 100km/h) its perfectly fine. family friend works at a battery shop, and replaced the battery less than a year ago, and at the time said the alternator was putting out about 14.4v at idle (engine warm) and was told it was fine. i think its just that the batteries are small, and the alternator is small...

stock battery size and stock alternator...
 

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re: the brake light, there is a switch on the e-brake handle. Make sure that the red/black wire is still connected to the switch and not shorting out. When checking the fluid, make sure that it is at least at the height of the grill inside. On mine, if it gets below it, I will see the brake light come on when making a hard left hand turn.

Does your alternator light come on when you turn the key to the run position but before starting? If no, then you need to replace that light as it is needed for remote sensing by the alternator.

A good headlight mod is to re-wire your headlights and add relays. The stock wiring is just too weak and uses a switched ground which is also subject to problems. Here is a good link to follow
 

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Does your alternator light come on when you turn the key to the run position but before starting? If no, then you need to replace that light as it is needed for remote sensing by the alternator.
This wire provides a pre-charge to the alternator coils, as they are not powerful enough (magnetically) to provide the initial charge. It's called an exciter wire. Many alternators should have an exciter lead.
Some alternators (including the one on my 1600 8v sidekick/vitara engine) are "self-exciting" and will start to charge when the revs are high enough.
Without the wire, it will run ok at highway revs, but when doing around town driving, when you're sitting at traffic lights there will be no charge.

It's a bit of a stupid design as it runs through the dash light, so if the dash bulb goes, so does your alternator!
 

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what exactly does the alternator light look like? I assume it's in the center idiot light strip, but if it says ALT then I don't think mine lights...
 

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It is called a Charge Light in the FSM for the non-EFI models. From looking at page 21-2 in the FSM, it is to the left of the Oil Pressure light and to the right of the Brake Warning light. There are 7 lights across the bottom with a big gap between lights 3 & 4 so unsure of the exact placement.

I have a '91 and the light is in the center strip, but have no idea what the icon looks like as my battery is currently disconnected for other repairs. And frankly never paid much attention to it since it never came on while running. The light did work as I replaced all the dash bulbs about two years ago and checked it then.

And thanks Twiss for correcting me on the "exciter" wire. I didn't think remote sensing was correct at the time but I could not think of the correct term. Remote voltage sense is a connection to the alternator where the alternator detects the charging system voltage. On a Samurai this can result in the alternator receiving a lower voltage signal since the the wire is connected to the ignition rather than directly to the battery. This does not cause a big problem with the small stock alternators, but it you upgrade to a high output one, it can result in overcharging of your battery.
 
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