Too Much Voltage
#2714326
11/09/19 07:18 PM
11/09/19 07:18 PM
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Joined: Feb 2003
Posts: 16,117 Mesa, Arizona
dart4forte
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First, I hate wiring and electrical. 1974 Dodge D100. So, installed a new Autometer voltmeter. Wired into the ignition feed and wired to a good ground. Fired it up and it was reading 12-14 volts at idle and 14.5 at cruise. Anyway yesterday afternoon I was cruising down the freeway and noticed the VM reading 16.5, took the offramp and came to a stop. It read 16 at idle. Turned on the lights and it made no differance.
Today I replaced the voltage regulator with a spare I had. Still reads high. Switched alternators and I get the same. Went through and made sure all my grounds are tight. I even added a frond wire to one of the mounting bolt for the regulator. Cleaned up the ground foe the batter6 cable. Had the battery checked, it showed it had a bad cell. So, new battery. Came home and put it all together. Now, it idles at 14-14 volts and when driving it’s back to 16-17 volts.
Any suggestions?
“So if it’s on the internet it must be true”
Abe Lincoln
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Re: Too Much Voltage
[Re: dart4forte]
#2714352
11/09/19 09:04 PM
11/09/19 09:04 PM
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Joined: Jan 2003
Posts: 15,197 Omaha Ne
TJP
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Check the Ign. terminal on the regulator. It "senses" the available voltage and energizes the field windings in the alternator to bring the voltage up. A low reading at the terminal will cause an overcharge condition. Next I would check the reading across the battery. it "should " be very close to the ign terminal reading. if not try removing and reinstalling the bulkehead connector at the firewall and repeat the above tests Report back and we'll got from there
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Re: Too Much Voltage
[Re: TJP]
#2714361
11/09/19 09:39 PM
11/09/19 09:39 PM
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Joined: Feb 2003
Posts: 16,117 Mesa, Arizona
dart4forte
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Check the Ign. terminal on the regulator. It "senses" the available voltage and energizes the field windings in the alternator to bring the voltage up. A low reading at the terminal will cause an overcharge condition. Next I would check the reading across the battery. it "should " be very close to the ign terminal reading. if not try removing and reinstalling the bulkehead connector at the firewall and repeat the above tests Report back and we'll got from there Thanks
“So if it’s on the internet it must be true”
Abe Lincoln
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Re: Too Much Voltage
[Re: TJP]
#2714362
11/09/19 09:40 PM
11/09/19 09:40 PM
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Joined: Feb 2003
Posts: 16,117 Mesa, Arizona
dart4forte
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Check the Ign. terminal on the regulator. It "senses" the available voltage and energizes the field windings in the alternator to bring the voltage up. A low reading at the terminal will cause an overcharge condition. Next I would check the reading across the battery. it "should " be very close to the ign terminal reading. if not try removing and reinstalling the bulkehead connector at the firewall and repeat the above tests Report back and we'll got from there Am I checking with a volt meter?
“So if it’s on the internet it must be true”
Abe Lincoln
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Re: Too Much Voltage
[Re: dart4forte]
#2714397
11/09/19 11:54 PM
11/09/19 11:54 PM
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Joined: Aug 2003
Posts: 43,007 Bend,OR USA
Cab_Burge
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Bend,OR USA
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Do you trust that Autometer gauge to be accurate now? Check it out first against a real good V.O.M. I've had to many expensive Autometer mechanical race gauge that where NOT accuarte
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Too Much Voltage
[Re: Andrewh]
#2714428
11/10/19 03:29 AM
11/10/19 03:29 AM
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Joined: Feb 2003
Posts: 16,117 Mesa, Arizona
dart4forte
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yes use a volt meter. basically you are checking for a voltage difference in the sensing line or the field line.
1 field line goes to the vr the other ties back into the key on power from the ign 1 on the key.
here is how I look for voltage drops.
with the car on run, but not running. you check with the voltmeter using the battery ground. check against the pos of the battery, see what the voltage reads. then check voltage at the sensing line of the VR. Then check voltage at the field of the alt. with the vr plug pulled, (assuming this is a dual field alt using the later triangle plug vr), one of the fields will be 0, the other should be battery voltage. you can then trace back to the bulkhead to see if that is causing the issue or a bad connection somewhere else.
you can also transfer the ground to the body of the vr as well when checking the sensing line voltage and to the body of the alt for the field to see if there is a ground issue.
generally speaking I would bet you will see almost 1 volt drop meaning you need to clean up the bulkhead connector or find the bad connection. if swaping the ground gives you a bigger volt diff, then you have a bad ground somewhere. I should also add the truck idles ok but when put in either reverse or drive the engine dies.
“So if it’s on the internet it must be true”
Abe Lincoln
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Re: Too Much Voltage
[Re: Andrewh]
#2714457
11/10/19 09:55 AM
11/10/19 09:55 AM
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Joined: Feb 2010
Posts: 1,645 Phila. Pa.
Mattax
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Removing the connector from the regulator creates an open circuit. No current flows. The voltage at both connector terminals should be within tenths of the battery. The only drop would be from the current flowing to the ignition, which is only a couple amps.
In this situation, it probably makes more sense to measuring voltage at the alternator output stud to the regulator input with the engine running. The closest locations to measure the votlage being sensed by the regulator while running are the alternator brush with the 'ignition' wire, and the ballast resistor connection with the same. The 'ignition' or 'run' wires are usually dark blue or dark blue with a white tracer. But being a truck, it might be different. Later trucks used a different color, but my guess is '74 is the same as cars of those years.
If the voltage developed by the alternator increases with increasing rpm and vica versa, then it is almost certainly a regulation issue. A small variance at low rpm is normal. But going above 15 Volts is not. If the second brush (usually connected to the green wire) gets grounded, then there is no voltage regulation. So check the brush terminal's insulator and also the insulation on the green wire to the regulator. If that's not it, then suspect the regulator.
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Re: Too Much Voltage
[Re: TJP]
#2714574
11/10/19 04:54 PM
11/10/19 04:54 PM
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Joined: Feb 2003
Posts: 16,117 Mesa, Arizona
dart4forte
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Ok, dug out my voltmeter. Static voltage on the battery is 12.7 volts. Fired the motor and I get 18.5 at idle. Checked the alternator and at idle I’m getting 18.5, run the motor up at around 1500 rpm and the reading was 22 volts. Took the alternator off and ran down to Orielys. On a short test the machine showed 16.5 volts. Overall the alternator tested bad.
Last edited by dart4forte; 11/10/19 04:56 PM.
“So if it’s on the internet it must be true”
Abe Lincoln
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Re: Too Much Voltage
[Re: dart4forte]
#2714602
11/10/19 07:01 PM
11/10/19 07:01 PM
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Joined: Aug 2003
Posts: 43,007 Bend,OR USA
Cab_Burge
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I Win
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Bend,OR USA
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You did good, test, test and test some more until you whup Murphys butt l
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Too Much Voltage
[Re: Cab_Burge]
#2714902
11/11/19 06:46 PM
11/11/19 06:46 PM
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Joined: Feb 2003
Posts: 16,117 Mesa, Arizona
dart4forte
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Ok, changed out the alternator. Fired it up and it now runs ar idle 13.5 to 14.5 however when the rpms go up it goes to 16 volts. I went ahead a pulled the bulkhead plugs. As suspected both the red white going in was burn’t at the spade and the same for the black wire that goes to the alternator. I have the bulkhead soaking in Evaporust. I did this on a 65 Chrysler I had and the contacts came out squeaky clean. I may just go ahead and replace both the red and black wires, drill out the bulkhead fitting and run the wires through the bulkhead.
Last edited by dart4forte; 11/11/19 06:48 PM.
“So if it’s on the internet it must be true”
Abe Lincoln
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Re: Too Much Voltage
[Re: mopars4ever]
#2715318
11/13/19 12:45 AM
11/13/19 12:45 AM
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Joined: Feb 2003
Posts: 16,117 Mesa, Arizona
dart4forte
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Check the plug on the ignition switch. I have seen quite a few melted causing issues. My 77 plymouth had a problem with overcharging and it was a melted blue wire at the bottom of the column grounding out. Plug on the ignition switch?
“So if it’s on the internet it must be true”
Abe Lincoln
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Re: Too Much Voltage
[Re: dart4forte]
#2715319
11/13/19 01:00 AM
11/13/19 01:00 AM
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Joined: Jan 2003
Posts: 3,122 Auburn WA
Dave_J
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Auburn WA
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Check the plug on the ignition switch. I have seen quite a few melted causing issues. My 77 plymouth had a problem with overcharging and it was a melted blue wire at the bottom of the column grounding out. Plug on the ignition switch? On the steering column is a flat plug. The Blue wire on my sons 1974 D200 was burnt. I cut them out and put a bullet connector inline.
Retired, US ARMY 1973-1994 ASE mechanic, Electrical 1994-1997 Retired GTE/VERIZON/FRONTIER 1997-2015
Posting cheap tech help (CRAP) here since Nov 97, 1000's of posts, some may be good.
03 Suzuki Burgman 650(Burger King) Scooter 65 Formula S Cuda 78 Little Red Express Truck 98 Buick Regal (wifes car)
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Re: Too Much Voltage
[Re: moparx]
#2715486
11/13/19 06:55 PM
11/13/19 06:55 PM
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Joined: Feb 2003
Posts: 16,117 Mesa, Arizona
dart4forte
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Ok, all up and running. I get 14 volts ar idle and 14.5 at cruse. Meter bounces a bit which give me reason to think there’s a hiccup in there. Got home ant had a crappy idle, finally died. Restarted now it dies when I put it in gear. Given I drove the truck hitting bumps leads me toward the bulkhead connector. At idle the battery is getting a charge around 14 voltsI’ll go out and check tomorrow. Also, since we changed out the steering column I’ll be checking that wiring as well.
“So if it’s on the internet it must be true”
Abe Lincoln
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