The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > 47 - Current classic GM Trucks > The 1967 - 1972 Chevrolet & GMC Pickups Message Board

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 07-13-2018, 08:18 PM   #1
mr.precision
Registered User
 
mr.precision's Avatar
 
Join Date: Feb 2018
Location: Prescott, AZ
Posts: 37
Alternator warm with ignition off 1967 C10

Bought this truck after sitting for 6 years in a barn. I've got it running pretty well.... 283 and a four speed....but the battery slowly discharges and the alternator is warm to the touch with the ignition off. Amp meter shows a slight discharge when driving. I tested the alternator and it appears good.
Checked all the wires - they look OK.
Voltage regulator is sealed so I cannot get inside to have a look.
2 questions:
What's a good brand regulator to look for? Does it make any difference as to the manufacture? Solid state or mechanical?
Also, what is the device located beneath the existing regulator? It's a cylinder probably 2-1/2" long and maybe 3/4" in diameter. This is a very original '67, so I wouldn't be surprised if it is OEM to the truck.
Thanks in advance.
Attached Images
 
mr.precision is offline   Reply With Quote
Old 07-13-2018, 08:54 PM   #2
Steeveedee
Senior Member
 
Steeveedee's Avatar
 
Join Date: Jan 2013
Location: Simi Valley, CA
Posts: 1,938
Re: Alternator warm with ignition off 1967 C10

That cylinder below the regulator is a "condenser"- a capacitor, used to reduce radio noise from the voltage regulator switching. I'd suspect that you have a failed diode in the alternator, or that the voltage regulator is bad. One of our guys has much more knowledge than I do about troubleshooting electrical; he'll likely be around soon with more on how to check that out properly.

How did you test the alternator to verify that it is good? I hope you didn't just pull a cable off the battery to see if the truck continued to run.
__________________
'70 Chevy 3/4T Longhorn CST 400/400/3.54 Custom Camper

"Orange Acres"
Steeveedee is offline   Reply With Quote
Old 07-13-2018, 11:57 PM   #3
mr.precision
Registered User
 
mr.precision's Avatar
 
Join Date: Feb 2018
Location: Prescott, AZ
Posts: 37
Re: Alternator warm with ignition off 1967 C10

Tested at an O'reilly's auto parts store. Ran the test twice. I don't know how reliable this test is, but it's the best I can do. I would think with a failed diode, the test would have "failed". They do like to sell replacement alternators.
mr.precision is offline   Reply With Quote
Old 07-14-2018, 01:36 AM   #4
VetteVet
Msgt USAF Ret
 
VetteVet's Avatar
 
Join Date: Jan 2005
Location: Kalamazoo, Michigan
Posts: 8,126
Re: Alternator warm with ignition off 1967 C10

To troubleshoot the charging system start with the regulator plug. Pull the plug off the regulator and test the brown wire on the end of the plug. It should read zero ohms with the key off and 12 volts with the key on. The red wire in the plug should have 12 volts on it key on or key off.

Plug the regulator back in and test the small plug on the alternator the same way. pull it out and look for 12 volts on the white wire key on and zero with the key off. The blue wire should be hot all the time. If the points in the regulator stick together it will keep the regulator coil energized and send power to the alternator even with the key off and the alternator will feet warm.

Now pull the large red wire off the alternator and do an ohms check between the large terminal and the body of the alternator. You should get near zero ohms in one direction and a large reading the other way when you reverse the leads.
If you get low lohms both ways then one of the diodes is shorted and allowing battery current to flow through the alternator windings to ground. This would cause the alternator to feel warm to the touch with the key off and it would also drain the battery.

Another good test is to connect a test light between the negative battery cable and the negative battery terminal. With the multimeter on amps, you need at least a 10 amp setting on the meter. With the key off look for a draw greater than .003 or 3MA. That's milliamps. You will probable see 1 or 2 amps if the diode is blown.

Then pull the regulator plug and see if the reading gets less than 2MA. If it stays high then pull the small plug off the alternator. Then if no change pull the large battery wire of the alternator and if you have a blown diode your in the field windings the meter will drop to .002 or less.

The diodes can fail two ways. They can conduct current both ways and the alternator may continue to function as normal except it will drain battery current to ground and drain the battery. This may get a pass reading from O'reillys but the alternator is still bad.

It can also fail by not conducting current either way which is the way most of them fail.

If your readings do not pass and you decide to get a new alternator or regulator, then consider converting to an SI or /cs style and improve you charging performance greatly.

We can walk you through the conversion since it is easy.
__________________
VetteVet

metallic green 67 stepside
74 corvette convertible
1965 Harley sportster
1995 Harley wide glide

Growing old is hell, but it beats the alternative.
VetteVet is offline   Reply With Quote
Old 07-14-2018, 08:52 AM   #5
davepl
Registered User
 
davepl's Avatar
 
Join Date: Aug 2006
Location: Redmond, WA
Posts: 5,998
Re: Alternator warm with ignition off 1967 C10

I will generally defer to Vettevet on electrical issues, so go with what he says above! In case he didn't cover it all, I've found that if you have a bad diode in the alternator, current will flow backward through the diode pack.

This can cause the alternator to heat up (esp. when running) and to kill the battery at rest. If also significantly decreases alternator output while running.
__________________
1970 GMC Sierra Grande Custom Camper - Built, not Bought
1969 Pontiac 2+2 427/390 4-speed Coupe
1969 Pontiac 2+2 427/390 4-speed Convertible
davepl is offline   Reply With Quote
Old 07-15-2018, 08:59 AM   #6
mr.precision
Registered User
 
mr.precision's Avatar
 
Join Date: Feb 2018
Location: Prescott, AZ
Posts: 37
Re: Alternator warm with ignition off 1967 C10

Thanks for the detailed explanation. Will check today and report findings.
mr.precision is offline   Reply With Quote
Old 07-17-2018, 09:41 AM   #7
mr.precision
Registered User
 
mr.precision's Avatar
 
Join Date: Feb 2018
Location: Prescott, AZ
Posts: 37
Re: Alternator warm with ignition off 1967 C10

Took a good regulator off oe of my other trucks and measured the voltage across the battery with the current set-up. At idle I was getting around 17 volts, and at fast idle close to 16.5 volts. Not good.
I then removed the two lines going through the radio suppression condenser, and connected them with an alligator clip.
Charge voltage went down to 15.2 at idle and 14.8 at fast idle. Oddly enough, the regulator "chatters" when coming off fast idle. The maximum voltage across the battery also seems to promote this chatter.
Next step is to try a used alternator from another truck I have and measure the voltage across the battery one more time. And, I still need to go through vette's check list and see if anything else is going on.

I suspect that the condenser was causing the high voltage in the initial test, and probably had been that way for years.
mr.precision is offline   Reply With Quote
Old 07-17-2018, 11:24 AM   #8
VetteVet
Msgt USAF Ret
 
VetteVet's Avatar
 
Join Date: Jan 2005
Location: Kalamazoo, Michigan
Posts: 8,126
Re: Alternator warm with ignition off 1967 C10

Quote:
Originally Posted by mr.precision View Post
Took a good regulator off oe of my other trucks and measured the voltage across the battery with the current set-up. At idle I was getting around 17 volts, and at fast idle close to 16.5 volts. Not good.
I then removed the two lines going through the radio suppression condenser, and connected them with an alligator clip.
Charge voltage went down to 15.2 at idle and 14.8 at fast idle. Oddly enough, the regulator "chatters" when coming off fast idle. The maximum voltage across the battery also seems to promote this chatter.
Next step is to try a used alternator from another truck I have and measure the voltage across the battery one more time. And, I still need to go through vette's check list and see if anything else is going on.

I suspect that the condenser was causing the high voltage in the initial test, and probably had been that way for years.
The condenser's main function is to smooth out the electronic chatter caused by the points inside the regulator, to prevent static in the radio speakers.
It sounds like yours failed and caused the points in the regulator to remain closed, which would account for the high voltage generated at idle. It amounts to the same thing as bypassing the regulator which is called "full fielding the alternator ".

When you bypassed the condenser you allowed the points to open and close like they normally do. When the points are open the alternator is not charging, and when they are closed it sends full voltage to the alternator. The regulator senses the system voltage and opens and closes the points very rapidly to regulate the charge voltage at 14.5 volts output give or take a volt or so.

It would seem like wiring in a new condenser may correct your problem.

I still say an internally regulated alternator will make you happier. A 12 SI off a mid eighties Camaro, S-10 pickup or any of a dozen GM vehicles in that genre or even one of the CS alternators from the early nineties would work.
__________________
VetteVet

metallic green 67 stepside
74 corvette convertible
1965 Harley sportster
1995 Harley wide glide

Growing old is hell, but it beats the alternative.
VetteVet is offline   Reply With Quote
Old 07-19-2018, 09:55 AM   #9
mr.precision
Registered User
 
mr.precision's Avatar
 
Join Date: Feb 2018
Location: Prescott, AZ
Posts: 37
Re: Alternator warm with ignition off 1967 C10

Thank you, Vettevet.
Any idea where I can locate one of these old style condensers? Did an internet search and came up with nothing but single wire noise suppression condensers. Even the local auto parts store doesn't show one like the original 2 wire unit.
mr.precision is offline   Reply With Quote
Old 07-19-2018, 03:45 PM   #10
Steeveedee
Senior Member
 
Steeveedee's Avatar
 
Join Date: Jan 2013
Location: Simi Valley, CA
Posts: 1,938
Re: Alternator warm with ignition off 1967 C10

Check it out here-

http://67-72chevytrucks.com/vboard/s...d.php?t=558016

Download the wiring diagrams and scroll down to diagram T-5283 (P 27). You will see that the black wire on the left side of the VR on the diagram ties into a bigger ground wire, as a chassis ground. You can ground the condenser directly to the body of the regulator now, like the rest of the world does.
__________________
'70 Chevy 3/4T Longhorn CST 400/400/3.54 Custom Camper

"Orange Acres"
Steeveedee is offline   Reply With Quote
Old 07-19-2018, 07:14 PM   #11
mr.precision
Registered User
 
mr.precision's Avatar
 
Join Date: Feb 2018
Location: Prescott, AZ
Posts: 37
Re: Alternator warm with ignition off 1967 C10

The brown wire coming off the bottom of the 4 prong connector on the regulator goes to the condenser front, then out the other side back into the wire harness. You can see this in the picture.
I don't follow what you are saying. The regulator is grounded, as you say, to the chassis via a black wire off the regulator body. The diagram does not show the condenser. I checked the 1967 diagram (T-5283 is 1968) but it is identical. Perhaps this isn't original to the truck, however the wiring looks original.
With everything hooked up, as it was, and a new regulator, charge voltage measured across the battery is correct at 14.8-15.0 volts. But the new regulator chatters when at idle, so obviously something isn't quite right.
Thanks for the help.
mr.precision is offline   Reply With Quote
Old 07-19-2018, 08:14 PM   #12
Steeveedee
Senior Member
 
Steeveedee's Avatar
 
Join Date: Jan 2013
Location: Simi Valley, CA
Posts: 1,938
Re: Alternator warm with ignition off 1967 C10

You got me on that one. I posted the '68 info because the '67 had a generator. I also made an assumption that the wire below went through the condenser, even though I didn't see the circuit symbol for a condenser. I apologize for that misinformation. In any event, I would just use a condenser that grounds at the regulator. I looked around the internet and had as much luck as you did on locating a condenser that looks like yours. It may well be that that style is obsolete for a reason.
__________________
'70 Chevy 3/4T Longhorn CST 400/400/3.54 Custom Camper

"Orange Acres"
Steeveedee is offline   Reply With Quote
Old 07-21-2018, 10:36 AM   #13
mr.precision
Registered User
 
mr.precision's Avatar
 
Join Date: Feb 2018
Location: Prescott, AZ
Posts: 37
Re: Alternator warm with ignition off 1967 C10

Calling VetteVet.
Any suggestions? If I do hook up a single wire condenser, how is it wired in? I cannot locate a 2 wire condenser, as pictured in the original post.
With the new regulator, everything appears to be working correctly. Charge voltage is right at 14.8 volts. I have the old condenser wired in as it was before, and I get intermittent chatter from the regulator at idle... which is pretty annoying.
I suppose I could leave it, and hope the new regulator doesn't get damaged as the old one was.
Thanks.
mr.precision is offline   Reply With Quote
Old 07-22-2018, 02:43 PM   #14
VetteVet
Msgt USAF Ret
 
VetteVet's Avatar
 
Join Date: Jan 2005
Location: Kalamazoo, Michigan
Posts: 8,126
Re: Alternator warm with ignition off 1967 C10

Quote:
Originally Posted by mr.precision View Post
Calling VetteVet.
Any suggestions? If I do hook up a single wire condenser, how is it wired in? I cannot locate a 2 wire condenser, as pictured in the original post.
With the new regulator, everything appears to be working correctly. Charge voltage is right at 14.8 volts. I have the old condenser wired in as it was before, and I get intermittent chatter from the regulator at idle... which is pretty annoying.
I suppose I could leave it, and hope the new regulator doesn't get damaged as the old one was.
Thanks.
The condenser should be tied into the brown wire at the no. 4 terminal on the regulator. It also mounts to the regulator body. I looked for a picture but couldn't find a good one.
__________________
VetteVet

metallic green 67 stepside
74 corvette convertible
1965 Harley sportster
1995 Harley wide glide

Growing old is hell, but it beats the alternative.
VetteVet is offline   Reply With Quote
Old 07-22-2018, 03:10 PM   #15
Steeveedee
Senior Member
 
Steeveedee's Avatar
 
Join Date: Jan 2013
Location: Simi Valley, CA
Posts: 1,938
Re: Alternator warm with ignition off 1967 C10

Just look at any under-hood picture of any truck on this board with an external voltage regulator that shows the condenser installed.
__________________
'70 Chevy 3/4T Longhorn CST 400/400/3.54 Custom Camper

"Orange Acres"
Steeveedee is offline   Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 09:51 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2018, vBulletin Solutions Inc.
Copyright 1997-2013 67-72chevytrucks.com