Wessilverado

Hey all, new member here with a bit of an odd question. I've tried searching, but most searches come up talking about the 05+ trucks with the ecm controlled voltage regulator.

My truck is a 2001 and came stock with the 105 amp alternator. The other day I swapped in a junkyard 145 amp unit from a 2004 tahoe. When I bought it, I took it to O'Reilly's first to get tested and they said it tested good (they had a really hard time operating the test equipment). Upon swapping it in, I've noticed my volt gauge bouncing around randomly. It rarely does this, but I can see my lights dimming as the gauge drops (it always flickers down).

It's been over 100 miles so I figure the battery would've died by now if the alternator was just bad outright. When it's reading normal (99.9% of the time) the gauge reads 1 tick over 14. It's just irritating me that it's doing it with the new alternator, and I'm afraid it'll leave me stranded sometime soon.

I disassembled the back of my 105 amp unit and was able to successfully remove the voltage regulator, but the one in the 145amp unit looks slightly different. They've got the same plugs, and mounting points however. Does anyone know if I could use the 105 regulator in place of the questionable 145 unit?

Thanks in advanced

mountainmanjoe

nope it was designed to handle 105A, not 145A .You'll burn it out.

Double check your connections, including the engine ground strap.

chem_man

Also, break out your Digital Multi-Meter (DMM) and set it to the AC Volts mode and the lowest range setting (hopefully it will be millivolts). With the engine running, the headlights turned on, and the HVAC blower motor set to the highest speed, measure the AC ripple voltage across the battery terminals. Next, with the black test lead connected to the negative battery terminal, place the red test lead on the battery terminal on the back of the alternator.

If either reading is over 50 mV, there is a problem with the alternator, and it will wind up killing the battery.

Hopefully, it will just be a bad electrical connection as mountainmanjoe suggests.

Good Luck!

Wessilverado

That's what I was afraid of, but admittedly I don't understand electricity as well as I'd like to, thanks for confirming for me.

Once daylight hits here I'll get out there with my meter and do some more testing

Wessilverado

Now that's an interesting test procedure that I never would've thought to try! Definitely gonna check this out as well

Wessilverado

So my AC ripple test showed 3 millivolts across the battery terminals, from battery negative to alternator positive, and alternator positive to alternator body.

Some other readings I took in DC volts were all normal. I did observe the voltage drop corresponding with the gauge flicker however. I also noticed the gas and temp gauge are starting to flicker as well

chem_man

OK on the 3 mV AC reading. That is excellent!

Be sure and check the connection between the small wire that comes off of the negative battery cable and goes to the body (should be to the right of the battery) and might be under some weatherstripping. That connection needs to be clean and tight. Be sure and look at the connection between the wire and the connector to make sure it has not been taken over by the green grunge.

2001 chevy silverado

(corrected from yesterday)

my 2001 voltage guage has never read 12V in it's life, btw

the guage is 9, 14, 19 with 10 marks in-between. just that alone should tell you they put no care into making the guage and it's a one peice chinese dash "cluster f" each mark is 1/2 V.

I usually read 16V just after starting, 15V when arriving home (2 marks lower). 16V arriving home (a 1/2V higher when starting) if there's an issue like weak battery.

but as far *** accuracy versus precision on a 2001 guage? nah, it's baked it's averaged don't try to make it "equal to the right accuracy value". use your dmm on the batt or wherever and compare it with the dash. don't worry if they are different. know your batt voltage versus your charging voltage using dmm, sure.

Oh, i'm shakin!

Wessilverado

Sorry for disappearing, works been busy and I also recently picked up one of those neat little Japanese mini trucks.

Anyway, the gauge itself isn't the concern, I can see the lights dimming as well, so I know the voltage is unstable.

Honestly the Silverado has been at my job for like 3 weeks now, so once I get it home I'll just order a voltage regulator and swap it