Amp meter reads discharge - Team Camaro Tech
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post #1 of 13 (permalink) Old Mar 3rd, 11, 01:05 PM Thread Starter
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Amp meter reads discharge

i installed factory style center console gauges in my 69 and the amp meter reads discharge all the time at idle and only reads 0 if i rev it to 2000rpms. but then drops again when it comes back to idle. i had my alternator checked and it passed. its a 60 amp alternator.i am running a bunch of electronics. aftermarket air, electric fan, electric fuel pump, cd ignition, modern radio(nothing fancy). when they are all running at once the amp gauge reads -40 at idle! so is it time to get a bigger alternator or do i have some kind of wiring issue? i checked the voltage at the battery with everything running and it was down to 11.82

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post #2 of 13 (permalink) Old Mar 3rd, 11, 01:10 PM
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Re: amp meter reads discharge

What reading does the amp gauge show when everything is turned off and the key is out of the ignition?

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post #3 of 13 (permalink) Old Mar 3rd, 11, 01:14 PM Thread Starter
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Re: amp meter reads discharge

Quote:
Originally Posted by IRON MAN View Post
What reading does the amp gauge show when everything is turned off and the key is out of the ignition?
right dap in the middle at 0

some more info the amp gauge is wired one end at the horn relay the other on the + terminal ont he batt

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post #4 of 13 (permalink) Old Mar 3rd, 11, 05:40 PM
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Re: amp meter reads discharge

My guess is you just need to swap the wires in the back of the gauge and it will ready the opposite side, kind of like a flowmeter installed backwards.
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post #5 of 13 (permalink) Old Mar 3rd, 11, 07:02 PM
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Re: amp meter reads discharge

Do you have a stock wiring system, including the 12 gauge charging wire running from the horn relay to the positive battery terminal?

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post #6 of 13 (permalink) Old Mar 3rd, 11, 07:23 PM Thread Starter
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Re: amp meter reads discharge

Quote:
Originally Posted by Mark C View Post
Do you have a stock wiring system, including the 12 gauge charging wire running from the horn relay to the positive battery terminal?
I dunno about that I ran my own wires for the amp gauge

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post #7 of 13 (permalink) Old Mar 3rd, 11, 07:26 PM
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Re: amp meter reads discharge

If the alternator is of the original design of being externally regulated, this is normal operation as the alt is not reg'd enough during idle to supply the current needed, the battery supplies what the alt can't. This leads to the 12 VDC reading at the battery posts with all accessories on at idle rpm.

Ammeter is hooked up correctly, abeit, the wire on the battery post should be on the junction block next to the battery. Rev up the engine/alt, voltage should rise. As said, normal operation for the original equipment installed at the factory when car was made.

You can simply do one of two things; 1) install an electronic voltage regulator, Wells P/N VR715, plug & play, 2) disconnect the ext regulator, and to the connector removed, jumper the two inside terminals and jumper the two outside terminals, and get a jumper connector from 10DN to a 10SI/12SI alt, and install the same 10SI/12SI alt. Either one of these two changes will improve the electrical system. But, with all accessories on, you would still only get 13 VDC at battery at idle. As accessories are turned off, voltage comes up.

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post #8 of 13 (permalink) Old Mar 3rd, 11, 07:55 PM
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Re: amp meter reads discharge

IMO your alternator is too small for the electronics you listed and your charging system needs to be upgraded. I would start with a 12SI as Everett suggested and use the upgraded charging system detailed on the MADelectrical.com site. You can buy the 12SI for about $95 at most parts houses. The upgraded system is great for modern accessories. While you are at it add some relays for the lights and fan if you haven't already.

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post #9 of 13 (permalink) Old Mar 4th, 11, 08:08 AM
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Re: Amp meter reads discharge

Autozone sells the 12SI for about $50 with a lifetime warranty.

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post #10 of 13 (permalink) Old Mar 16th, 11, 03:36 PM Thread Starter
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Re: Amp meter reads discharge

so i got a powermaster 140 amp alternator and installed it. now i am getting 13 volts at idle with all my electronics running where before i was only gettin 10.9 but my amp gauge still reads -40 discharge. i called powermaster and they suggested running a ground from the body of the alt to the bat but that didnt do anything. any suggestions?

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post #11 of 13 (permalink) Old Mar 16th, 11, 06:26 PM
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Re: Amp meter reads discharge

If you turn off the engine and turn on a heavy load, like headlamps, the ammeter should show a discharge. If it does, ammeter hooked up correctly.

If ammeter reads still discharge with engine running, what is the multimeter reading across the battery terminals?
From the alt BATT post to the positive post read?
What does negative post to alt case read?
Both above should be less than 0.4 volts.

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post #12 of 13 (permalink) Old Mar 16th, 11, 08:22 PM Thread Starter
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Quote:
Originally Posted by Everett#2390 View Post
If you turn off the engine and turn on a heavy load, like headlamps, the ammeter should show a discharge. If it does, ammeter hooked up correctly.

If ammeter reads still discharge with engine running, what is the multimeter reading across the battery terminals?
From the alt BATT post to the positive post read?
What does negative post to alt case read?
Both above should be less than 0.4 volts.
Yeah it shows discharge like you said. I checked the the spots you suggested all read 0.00

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post #13 of 13 (permalink) Old Mar 17th, 11, 04:11 AM
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Re: Amp meter reads discharge

In the first post, you said you measured 12 volts - is this at the battery terminals?
Post 6, you ran some wires for the ammeter or alt hook-up - describe what you installed, as in, point-to-point per wire.

OE ammeter has two wires, one connects to the horn relay buss bar, the second wire connects to the battery junction block. The gauge measures the millivolt drop of the current running through the rad support #10 AWG wire, red one. One of the new wires may be in the wrong place.

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