AMPS Gauge / System test - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**RPOZ11** · 11-20-2014, 01:05 AM

Ok, just installed my GM Tach Dash assembly into my 75.

What is the best way to load test the system to ensure it is working correctly?

At this moment, the Tach works, oil line pressure working, gas gauge works.

The AMP gauge needle isn't moving.

Proper procedures to test the system?

Thanx

**Corts60** · 11-20-2014, 01:55 AM

The AMP gauge will only move if there is a load on the system, AKA the battery is low and is charging. Otherwise it will hover right in the middle constantly.

**RPOZ11** · 11-20-2014, 02:42 AM

Ok, thanx for that.
Had some discussion tonite with a friend.
The AMP Gaugeis is in a stock 73-75 Chevy Truck:
We used an original GM dash harness for the Amps system.
We purchased a reproduction wiring harness from AutoWire.
Front Light Harness all the way back to the tail lamp harness.
So, everything is brand new, for the exception of the under dash GM harness.
All is working.
Tach gauge : working.
Temp gauge : working.
Gas gauge : working.
Amp gauge : stands straight up with NO movement.

Now...
The Alt is a brand new rebuild; "0" miles.
Starter : Brand New rebuild GM unit.
Battery is the one that came with the truck.
Will replace that shortly with a new one.

What load tests can we do to ensure proper functionality of the AMP system?

tlawre87 · 11-20-2014, 03:03 PM

Way I always load test my system: Lights on with high beams, radio on, fan on max speed, AC on if possible. Granted this test is going to more see if the alternator is putting out good voltage. I'd still expect a drop in the ammeter though.

To add Id be using a voltmeter/Ammeter separately just to make sure you are seeing the voltage drops.

franken · 11-20-2014, 10:53 PM

I'd measure voltage across the gauge, and from each terminal to ground. Write down exactly what you get.
The reading across should be very low, maybe .5-2V, and the readings to ground very similar, differing by the reading across.
If you can't get to the terminals, a wiring diagram should show where to measure on the firewall connector under the hood.

justcuz · 11-22-2014, 06:02 PM

You can also test alternator output by using a volt meter off the back of the alternator (on the heavier gauge single wire) as you increase the load, the charge voltage should increase. Many times the amp gauge will drop minimally with a lot of load on it. This is why amp meters later became voltmeters on dash gauges.

11-20-2014, 01:05 AM	#1
RPOZ11 72 BB C30 Super LongHorn Join Date: Nov 2002 Location: Chavez Ravine Posts: 1,606	AMPS Gauge / System test Ok, just installed my GM Tach Dash assembly into my 75. What is the best way to load test the system to ensure it is working correctly? At this moment, the Tach works, oil line pressure working, gas gauge works. The AMP gauge needle isn't moving. Proper procedures to test the system? Thanx __________________ 72 BB C/30 Longhorn Super HO72 No-Spin, #'s matching, Tilt, Tach, AC, AM/FM HO72 build : http://67-72chevytrucks.com/vboard/s...d.php?t=714492 2017 SS

11-20-2014, 01:55 AM	#2
Corts60 Just here to tinker Join Date: Jun 2008 Location: Holland, MI Posts: 3,697	Re: AMPS Gauge / System test The AMP gauge will only move if there is a load on the system, AKA the battery is low and is charging. Otherwise it will hover right in the middle constantly. __________________ 78 C10 SWB Diesel #1 (wrecked)http://67-72chevytrucks.com/vboard/s...1978+silverado 78 C10 SWB Diesel #2 (sold)http://67-72chevytrucks.com/vboard/s...d.php?t=650751 60 GMC Suburban (sold)http://67-72chevytrucks.com/vboard/s...d.php?t=445526 60 GMC 1000 (sold)http://67-72chevytrucks.com/vboard/showthread.php?t=298235 67 GMC 1500 (sold) http://67-72chevytrucks.com/vboard/s...d.php?t=803695 73 Chevy C20(Daily)http://67-72chevytrucks.com/vboard/s...d.php?t=852767 86 Suburban(summer unit) http://67-72chevytrucks.com/vboard/s...d.php?t=810697 88 Suburban 4x4(sold)

11-20-2014, 02:42 AM	#3
RPOZ11 72 BB C30 Super LongHorn Join Date: Nov 2002 Location: Chavez Ravine Posts: 1,606	Re: AMPS Gauge / System test Ok, thanx for that. Had some discussion tonite with a friend. The AMP Gaugeis is in a stock 73-75 Chevy Truck: We used an original GM dash harness for the Amps system. We purchased a reproduction wiring harness from AutoWire. Front Light Harness all the way back to the tail lamp harness. So, everything is brand new, for the exception of the under dash GM harness. All is working. Tach gauge : working. Temp gauge : working. Gas gauge : working. Amp gauge : stands straight up with NO movement. Now... The Alt is a brand new rebuild; "0" miles. Starter : Brand New rebuild GM unit. Battery is the one that came with the truck. Will replace that shortly with a new one. What load tests can we do to ensure proper functionality of the AMP system? __________________ 72 BB C/30 Longhorn Super HO72 No-Spin, #'s matching, Tilt, Tach, AC, AM/FM HO72 build : http://67-72chevytrucks.com/vboard/s...d.php?t=714492 2017 SS

11-20-2014, 03:03 PM	#4
tlawre87 Registered User Join Date: Jun 2012 Location: Meeker, ok Posts: 146	Re: AMPS Gauge / System test Way I always load test my system: Lights on with high beams, radio on, fan on max speed, AC on if possible. Granted this test is going to more see if the alternator is putting out good voltage. I'd still expect a drop in the ammeter though. To add Id be using a voltmeter/Ammeter separately just to make sure you are seeing the voltage drops. __________________ Trevor 74 C20...work in progress. 04 Saturn Ion...Daily Driver Last edited by tlawre87; 11-20-2014 at 03:11 PM.

11-20-2014, 10:53 PM	#5
franken Registered User Join Date: Jun 2013 Location: Somewhere Posts: 3,123	Re: AMPS Gauge / System test I'd measure voltage across the gauge, and from each terminal to ground. Write down exactly what you get. The reading across should be very low, maybe .5-2V, and the readings to ground very similar, differing by the reading across. If you can't get to the terminals, a wiring diagram should show where to measure on the firewall connector under the hood.

11-22-2014, 06:02 PM	#6
justcuz Registered User Join Date: May 2008 Location: Alta Loma, Ca. Posts: 930	Re: AMPS Gauge / System test You can also test alternator output by using a volt meter off the back of the alternator (on the heavier gauge single wire) as you increase the load, the charge voltage should increase. Many times the amp gauge will drop minimally with a lot of load on it. This is why amp meters later became voltmeters on dash gauges.

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