Volts but no amps????? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

WRMZ71 · 12-14-2003, 01:46 PM

I was Playing with my truck the other day trying to figure out why my dang dash regulator light is coming on. The alternator is pumping out about 14.5 volts which is good but the light still comes on. I took it to autozone and had them put there machine on it and volts came out good but it's only pushing 9 amps. They should be pushing 60 amps or so. I got the external regulated alternator on it. 71 C-10. Would anybody know why I'm not getting amps but i'm getting plenty of voltage. The autozone guy said it's a wire but i went through cleaned the grounds and checked my wires and everything comes out ok. Any ideas????

JimKshortstep4x4 · 12-14-2003, 03:15 PM

If I understand the problem, you have a light instead of a guage and the light stays on all the time. The alternator puts out the 9 amps. Where was this checked at?

If the regulator is good, the wires are good then my thought would be to test the diode banks in the alternator. (Or just replace the alternator).

Jim

WRMZ71 · 12-14-2003, 06:37 PM

Jim............Yes i have the dummy light but i also have a set of gauges installed under the dash. I had a multimeter awhile back and i tested voltage at the battery which while running was 14.6 that was approx the same coming out of the alternator when i tested it right there. As far as the amps goes I had that tested at autozone and he tested right off the battery. I forgot all about the amps when i had the multimeter

I should have tested for amps coming straight off the alternator. Is that what I should do? and what can I do if I get good amps coming right out of the alternator??

jef5150 · 12-14-2003, 08:05 PM

you sure he did your test correct??.....that 9 amp reading would be correct at "idle",,,,,but to test amperage output, your truck should be "underload" ,lights, blower motor, "on",etc,,,,,and rpm should be at least 2000rpm,,,,,,,,,just a thought,,,,,,,, jeff

JimKshortstep4x4 · 12-14-2003, 09:11 PM

As Jeff5150 put it you need the alternator under load to test.

When they tested at the battery, they were testing the whole system including the regulator. Unless there is a load on the system amps, would be expected to be low, (as the battery reaches full charge, the regulator will cut back on the amps going to the battery, otherwise the electrolyte will be boiled out).

If you have an amp meter that is adequate , I would suggest checking the output again under load. The amp meter that I use is
a Snap-On that reads when you place it over the wire so it cannot be burned out as a direct wired one can if it isn't able to handle the amperage. The factory amp gauge is a shunt type and reads amperage based on resistance in the wire so if you have one of those it can be made to work also. I am not sure about using a multimeter as generally they read small amperage.

A loose fan belt can do the same thing as you describe, (full voltage, low amps).

Good luck!

Jim

12-14-2003, 01:46 PM	#1
WRMZ71 Cause the Chicks DIG IT!! Join Date: Nov 2003 Location: Beaufort SC Posts: 509	Volts but no amps????? I was Playing with my truck the other day trying to figure out why my dang dash regulator light is coming on. The alternator is pumping out about 14.5 volts which is good but the light still comes on. I took it to autozone and had them put there machine on it and volts came out good but it's only pushing 9 amps. They should be pushing 60 amps or so. I got the external regulated alternator on it. 71 C-10. Would anybody know why I'm not getting amps but i'm getting plenty of voltage. The autozone guy said it's a wire but i went through cleaned the grounds and checked my wires and everything comes out ok. Any ideas????

12-14-2003, 03:15 PM	#2
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	If I understand the problem, you have a light instead of a guage and the light stays on all the time. The alternator puts out the 9 amps. Where was this checked at? If the regulator is good, the wires are good then my thought would be to test the diode banks in the alternator. (Or just replace the alternator). Jim

12-14-2003, 06:37 PM	#3
WRMZ71 Cause the Chicks DIG IT!! Join Date: Nov 2003 Location: Beaufort SC Posts: 509	Jim............Yes i have the dummy light but i also have a set of gauges installed under the dash. I had a multimeter awhile back and i tested voltage at the battery which while running was 14.6 that was approx the same coming out of the alternator when i tested it right there. As far as the amps goes I had that tested at autozone and he tested right off the battery. I forgot all about the amps when i had the multimeter I should have tested for amps coming straight off the alternator. Is that what I should do? and what can I do if I get good amps coming right out of the alternator??

12-14-2003, 08:05 PM	#4
jef5150 Inline 69 Join Date: Apr 2003 Location: valleysprings,california Posts: 1,018	you sure he did your test correct??.....that 9 amp reading would be correct at "idle",,,,,but to test amperage output, your truck should be "underload" ,lights, blower motor, "on",etc,,,,,and rpm should be at least 2000rpm,,,,,,,,,just a thought,,,,,,,, jeff

12-14-2003, 09:11 PM	#5
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	As Jeff5150 put it you need the alternator under load to test. When they tested at the battery, they were testing the whole system including the regulator. Unless there is a load on the system amps, would be expected to be low, (as the battery reaches full charge, the regulator will cut back on the amps going to the battery, otherwise the electrolyte will be boiled out). If you have an amp meter that is adequate , I would suggest checking the output again under load. The amp meter that I use is a Snap-On that reads when you place it over the wire so it cannot be burned out as a direct wired one can if it isn't able to handle the amperage. The factory amp gauge is a shunt type and reads amperage based on resistance in the wire so if you have one of those it can be made to work also. I am not sure about using a multimeter as generally they read small amperage. A loose fan belt can do the same thing as you describe, (full voltage, low amps). Good luck! Jim



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.