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wiring a ammeter gauge..


eurotrash
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So, let me start by saying that I haven't installed an aftermarket gauge since the 1990's, and the early '90's at that..

I have finally completed my vintage Motometer Ammeter, Temp, and Oil Pressure gauge set. (the little lights are for front and rear fogs) I am looking for help on how to wire these gauges up...?

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I know this is a three part question, but I'm totally a scared little girl around auto electric.

Here is the Ammeter..

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the question I have initially is how to I add this to my car? And secondly, will it work with the stock, or even the e30 alt, and be accurate? If not, can something like a resistor be added to make it work accurately?

Here is the Temp..should be fine. I just need to know what to do to get it to work..

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And finally the Oil Pressure gauge with dual sender... I have an adapter for the motor. But once again, I need wiring insight.

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As far as the gauge lights go, can I just use the pigtail from a Tii harness to tap into the cluster and daisy chain them all so I have dimming capabilities?

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LOL. figures. I thought the 5 bar would cut it.. shizzz. I fell for the little 40mm guys last year when I saw the first one.

The Tii clock is Motometer.. thought it was a neat touch. Bleh. FKN eBay here we come.. Unless anyone has a batch o' clever ideas.

it will do it for 99% of your driving time...unless your motor stay cold all the time ;)

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LOL. figures. I thought the 5 bar would cut it.. shizzz. I fell for the little 40mm guys last year when I saw the first one.

The Tii clock is Motometer.. thought it was a neat touch. Bleh. FKN eBay here we come.. Unless anyone has a batch o' clever ideas.

it will do it for 99% of your driving time...unless your motor stay cold all the time ;)

I like yer optimism Mr. Allen. I like yer way o' thinkin'.

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Well an ammeter measures current inline so it's not going to be fun to wire up. Modern cars have an inductive ammeter which straps to the battery cable and figures out the current without touching the wire, so to speak. The vintage ones like yours are absolutely scary:

theoretically you will take your battery cable and route it through the gauge. Of course you can't physically do that so you'll pick some circuit to route through it (ex: main "+" wire to the battery, bolted to the positive side). That's invasive to your wiring, puts massive amounts of current through a dinky gauge in your dash, and if you ever short it out by accident or get rain in there, you're in trouble.

My advice is to not install it ; ) A volt meter might be more helpful ("is my alternator charging? how much drop do I get when the lights are turned on?") and that's of course much simpler to wire up since it measures in parallel and doesn't draw any significant current!

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The reason everyone says to ditch the ammeter and switch to a voltmeter is that an ammeter needs to be in line with all of the car's power in order to give you a reading. This means that if it were to break, your whole car would lose power.

A voltmeter, however, can be run in parallel with the car's power system and is therefore normally insignificant to the car's power system.

It can be argued as to which gauge gives the user 'better' information as far as the health of the car's electrical system.

I like to think of the information provided by the gauges as entirely different scales (which they are), that each have both 'good' and 'bad' readings.

IMHO, my car came stock with an ammeter, and I disconnected it because I wanted to simplify the car's electrical gremlins.

HTH,

Jay

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Guest Anonymous

Just a thought ... if you want to be an automotive hacker ....

JAMECO, the electronics catalog supplier, sells a precision "current shunt" that can be put in series with the battery line at a remote location, ie near the battery. If you put a voltmeter accross it, it converts one amp of current flow into 1mv of voltage. A 50mv meter then reads one amp per millivolt and 50 amps full scale. If there is a catastrophic failure, you can short the shunt with wire and be on the road again. If you pull more than 50amps through it, such as starting the car, it won't fail, the meter just pegs in the positive flow direction for a moment until the start cycle is done.

The shunt is about $25 and they still have them. I forget the exact name they list it under but I just priced it last month. Customer service knows what it is called.

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Guest Anonymous

Just another thought ... the other poster said that the ammeter measures the flow in the battery lines ... actually, I think, it measures the 'charge' flow to the battery. It sets between the alternator and the battery and indicates charging current. I don't think the draw to the starter motor flows through the ammeter. That is quite a load and might destroy even the measurement shunt described above.

On my car, I'll have to check, there is a dedicated positive wire that feeds the starter motor. This is different from the other positive wire that feeds the other circuits. You don't want the starter motor feed flowing through the ammeter. If your car is wired with heavier loads, such as HID lamps, fogs, electrical cooling fan, or eleictric pump. you may have a larger load situation. In that case you could put one or more shunts in parallel and recalibrate the meter.

I did say automotive 'hacking' didn't I!

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