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bob8619 · 01-11-2014, 05:37 PM

Hey guys, just picked up a 72 C10 with the 350 a few days ago and I've been looking everything over. I searched but did not find any help so I decided to make this my first post.

I noticed last night that with the engine running I am getting 11.8v at the battery. I had the alternator tested at the the auto parts store and they said it passed everything so I figured ok the regulator is bad so I bought one. Installed the regulator and I'm still getting 11.8v while running. 12v when the engine is off.

This may be the wrong way of testing the alternator but I put my volt meter to it, one to where the nut connects the red wire and another to each of the other contacts, between the nut and one of the contacts I get 11.8 volts. Engine running by the way, different RPMS and it stays 11.8

Is this alternator bad or did I test it wrong?

Thanks guys
Bob

bob8619 · 01-11-2014, 05:45 PM

A bit of added info, the battery has not died on me since I've owned it and I've had the lights on and radio on A LOT. Not to mention I have had it running a lot as well.

70LonghornCST · 01-11-2014, 05:47 PM

Hi Bob, and welcome!
At first in reading your post, I was thinking it may be experiencing a draw due to erratic idling. My Plymouth does just that. However, you state that with the "Engine running by the way, [you get] different RPMS and it stays 11.8," makes me think it may be the alternator or voltage regulator. If the RPMs bounced with the different it COULD be a draw from a poorly adjusted carb or something else. Electrical is not my area of expertise. I know that some of our board gurus will chime in shortly.
Again, welcome and glad to have you here!
-Richard

bob8619 · 01-11-2014, 05:50 PM

Thanks for the welcome!

And just to be clear, when I said different RPMs I meant when I change the RPMs its the same voltage. Not that the rpms are bouncing around on their own.

bob8619 · 01-11-2014, 09:50 PM

I took it to another store and they also tested it and said it was good. I noticed though that one of the connector tabs was loose and would slide upward. I figured that probably rattles when the engine is on and doesnt make good contact. I decided to just buy a new alternator and now I get 13.4 volts at idle.

Mathew21 · 01-11-2014, 09:53 PM

Welcome, Sounds like you fixed your problem.

bob8619 · 01-11-2014, 09:54 PM

Thanks Mathew21. I have more problems but I dont know if I should start a new thread or add here. hmmmm

spatz · 01-11-2014, 11:33 PM

Welcome to the site. Just start a new post and with the caption of what you need would be the easiest way to get the right answers.

bob8619 · 01-15-2014, 12:34 AM

Hi guys. Been chasing other issues and tested my battery tonight while running. 12.4 at idle and no rise in voltage til probably 2000rpm. Any other ideas? Im at a loss

**70cst** · 01-15-2014, 02:34 AM

Hey bob8619
...

to the forums and

from Ohio ...

**Racer2172** · 01-15-2014, 02:51 PM

Some alternators dont start charging till over certain RPMS. Could be the reason.

bob8619 · 01-15-2014, 02:57 PM

I guess it was a problem with one of my grounding wires. Ran new grounds and now I'm at 14.4 at idle.

**Racer2172** · 01-15-2014, 04:52 PM

Good grounds are key in electrical flow. I personally ground block to frame and block to cab as well as battery negative post directly to the engine.

bob8619 · 01-15-2014, 05:09 PM

It still acts kinda funny. When I first start it and even while its choked and running about 1500rpm its saying 12.x volts. When it comes down to regular idle and I rev the engine then it'll go to 14.xx volts. Is this one of those that have to be excited before putting out higher voltage?

01-11-2014, 05:37 PM	#1
bob8619 Registered User Join Date: Jan 2014 Location: Ft Myers Florida Posts: 571	New guy Hey guys, just picked up a 72 C10 with the 350 a few days ago and I've been looking everything over. I searched but did not find any help so I decided to make this my first post. I noticed last night that with the engine running I am getting 11.8v at the battery. I had the alternator tested at the the auto parts store and they said it passed everything so I figured ok the regulator is bad so I bought one. Installed the regulator and I'm still getting 11.8v while running. 12v when the engine is off. This may be the wrong way of testing the alternator but I put my volt meter to it, one to where the nut connects the red wire and another to each of the other contacts, between the nut and one of the contacts I get 11.8 volts. Engine running by the way, different RPMS and it stays 11.8 Is this alternator bad or did I test it wrong? Thanks guys Bob

01-11-2014, 05:45 PM	#2
bob8619 Registered User Join Date: Jan 2014 Location: Ft Myers Florida Posts: 571	Re: New guy A bit of added info, the battery has not died on me since I've owned it and I've had the lights on and radio on A LOT. Not to mention I have had it running a lot as well.

01-11-2014, 05:47 PM	#3
70LonghornCST Moderator Join Date: Jun 2008 Location: Modesto, CA Posts: 5,775	Re: New guy Hi Bob, and welcome! At first in reading your post, I was thinking it may be experiencing a draw due to erratic idling. My Plymouth does just that. However, you state that with the "Engine running by the way, [you get] different RPMS and it stays 11.8," makes me think it may be the alternator or voltage regulator. If the RPMs bounced with the different it COULD be a draw from a poorly adjusted carb or something else. Electrical is not my area of expertise. I know that some of our board gurus will chime in shortly. Again, welcome and glad to have you here! -Richard __________________ 2018 Chevy Crew Cab 2006 Impala SS 1965 Plymouth Sport Fury 1970 Chevy Longhorn Bucket Seats Shoulder Belts Front Tow Hooks Factory Air Factory Speedwarning, Tach & Vaccum Factory Tilt CST Package AM/FM Radio Bumper Guards Richard 70 Longhorn CST Build Adding an AM/FM Decal

01-11-2014, 05:50 PM	#4
bob8619 Registered User Join Date: Jan 2014 Location: Ft Myers Florida Posts: 571	Re: New guy Thanks for the welcome! And just to be clear, when I said different RPMs I meant when I change the RPMs its the same voltage. Not that the rpms are bouncing around on their own.

01-11-2014, 09:50 PM	#5
bob8619 Registered User Join Date: Jan 2014 Location: Ft Myers Florida Posts: 571	Re: New guy I took it to another store and they also tested it and said it was good. I noticed though that one of the connector tabs was loose and would slide upward. I figured that probably rattles when the engine is on and doesnt make good contact. I decided to just buy a new alternator and now I get 13.4 volts at idle.

01-11-2014, 09:53 PM	#6
Mathew21 Registered User Join Date: May 2010 Location: Clinton township, MI Posts: 1,192	Re: New guy Welcome, Sounds like you fixed your problem.

01-11-2014, 09:54 PM	#7
bob8619 Registered User Join Date: Jan 2014 Location: Ft Myers Florida Posts: 571	Re: New guy Thanks Mathew21. I have more problems but I dont know if I should start a new thread or add here. hmmmm

01-11-2014, 11:33 PM	#8
spatz Registered User Join Date: Mar 2009 Location: Flint, Mi Posts: 200	Re: New guy Welcome to the site. Just start a new post and with the caption of what you need would be the easiest way to get the right answers.

01-15-2014, 12:34 AM	#9
bob8619 Registered User Join Date: Jan 2014 Location: Ft Myers Florida Posts: 571	Re: New guy Hi guys. Been chasing other issues and tested my battery tonight while running. 12.4 at idle and no rise in voltage til probably 2000rpm. Any other ideas? Im at a loss

01-15-2014, 02:34 AM	#10
70cst Senior Member Join Date: Feb 2001 Location: New Madison, Ohio Posts: 21,372	Re: New guy Hey bob8619 ... to the forums and from Ohio ... __________________ A husband can be right...or...A husband can be happy. 67-72 Chevy and GMC Trucks...The Classic Truck for the Classic Folk. 1970 CST Two tone green, 402BB, 400 Automatic, Tach, Buckets, AC, AM-FM, Tilt, GM CB, GM 8 Tract, LWB, etc JOHN 17:3...The better side of "LIFE" Remember: Everyday is a good day...Some are just gooder!

01-15-2014, 02:51 PM	#11
Racer2172 Senior Member Join Date: Nov 2011 Location: Yuma, AZ Posts: 319	Re: New guy Some alternators dont start charging till over certain RPMS. Could be the reason. __________________ 65 C-10 Times gone by(Sons truck)http://67-72chevytrucks.com/vboard/s...92#post6164692 70 C-30 Tow truck AKA Highlighter 02 Silverado 2500 HD CUCVII Tow Rig/DD 1968 C10 Project Quarantine http://67-72chevytrucks.com/vboard/s...d.php?t=804800 1980 Buick Regal Dirt Stock car

01-15-2014, 02:57 PM	#12
bob8619 Registered User Join Date: Jan 2014 Location: Ft Myers Florida Posts: 571	Re: New guy I guess it was a problem with one of my grounding wires. Ran new grounds and now I'm at 14.4 at idle.

01-15-2014, 04:52 PM	#13
Racer2172 Senior Member Join Date: Nov 2011 Location: Yuma, AZ Posts: 319	Re: New guy Good grounds are key in electrical flow. I personally ground block to frame and block to cab as well as battery negative post directly to the engine. __________________ 65 C-10 Times gone by(Sons truck)http://67-72chevytrucks.com/vboard/s...92#post6164692 70 C-30 Tow truck AKA Highlighter 02 Silverado 2500 HD CUCVII Tow Rig/DD 1968 C10 Project Quarantine http://67-72chevytrucks.com/vboard/s...d.php?t=804800 1980 Buick Regal Dirt Stock car

01-15-2014, 05:09 PM	#14
bob8619 Registered User Join Date: Jan 2014 Location: Ft Myers Florida Posts: 571	Re: New guy It still acts kinda funny. When I first start it and even while its choked and running about 1500rpm its saying 12.x volts. When it comes down to regular idle and I rev the engine then it'll go to 14.xx volts. Is this one of those that have to be excited before putting out higher voltage?



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