Voltage too high...

classic boost

Founding Member

Feb 3, 1999

709

0

0

canton, oh

Jun 28, 2007

#1

• Jun 28, 2007

• #1

it's charging at 17.5v. i replaced the volt reg, but it's still doing it. any other culprits?

thanks.

 

F

ForceFed70

That's why they call it "dope"

Founding Member

Dec 6, 1999

4,818

1

69

BC Canada

Jun 28, 2007

#2

• Jun 28, 2007

• #2

Regulator is what controls the voltage.

Are you sure the alternator/regulator is wired correctly? I suppose it could be a problem with the alternator itself (ignoring control signal from regulator).

Also, verify that your meter is OK. There's alot of AC "Ripple" in the charging circuit which could be throwing off your meter.

 

2nd Mustang

Founding Member

Feb 24, 2002

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46

Southern California

Jun 28, 2007

#3

• Jun 28, 2007

• #3

Is that reading on a gauge in the dash or a voltmeter reading right at the battery?

 

classic boost

Founding Member

Feb 3, 1999

709

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canton, oh

Jun 28, 2007

#4

• Jun 28, 2007

• #4

a digital voltmeter at the battery.

 

G

Grabber70Mach

Member

Jul 6, 2003

305

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17

Indian Head, MD

Jun 28, 2007

#5

• Jun 28, 2007

• #5

Are you sure you have the correct voltage regulator?

 

classic boost

Founding Member

Feb 3, 1999

709

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0

canton, oh

Jun 28, 2007

#6

• Jun 28, 2007

• #6

did they vary during the early years?

 

1

10secgoal

Active Member

Dec 1, 2003

2,801

3

49

San Diego

Jun 28, 2007

#7

• Jun 28, 2007

• #7

Dude I had the same problem. You could hear the fuel pump wig out. I tried multiple regulators, different alts, nothing worked. I ended up getting a GM internally regulated alt with a lifetime warranty from autozone.108 amp, easy bolt in. Just open the mounting hole to the head a little and bolt it in, wire up a BATT, and ign wire.

 

F

ForceFed70

That's why they call it "dope"

Founding Member

Dec 6, 1999

4,818

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69

BC Canada

Jun 29, 2007

#8

• Jun 29, 2007

• #8

paul302 said:

a digital voltmeter at the battery.

Click to expand...

Just for giggles, try measureing the voltage using an older analoge style guage/meter. The classic alternators didn't produce a very clean voltage and it could be messing with your meter. The older analogue meters are alot more forgiving in this regard.

 

3

351carlo

New Member

Mar 9, 2004

267

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Philadelphia

Jun 29, 2007

#9

• Jun 29, 2007

• #9

If the field line going to the alternator gets a full 12 volt signal, it will cause the alternator to overcharge.

I've done this purposely before using a jumper wire to test my regulator.

Check for a short between the field and the Batt terminal on the alternator.

The difference between regulators come with the higher amperage and then having a digital or mechanical. I run a 100 amp Ford alternator and matching digital regulator out of a mid 80's E-350 ambulance package. It's a nice unit.

 

classic boost

Founding Member

Feb 3, 1999

709

0

0

canton, oh

Jun 29, 2007

#10

• Jun 29, 2007

• #10

351carlo said:

Check for a short between the field and the Batt terminal on the alternator.

Click to expand...

that would be the two post next to each other on the alt, correct?

 

R

ron67fb

Founding Member

Aug 3, 2001

1,117

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36

SF Bay area, CA

Jun 29, 2007

#11

• Jun 29, 2007

• #11

Same problem here, 17v at the battery, and it was a short at the alternator harness. The harness that plugged into the alternator was bent too far and I guess was causing some pins/wires at the connector to short out. After a new regulator at $35 I finally fixed it by wiggling the connector then bending it at a less severe angle.

 

M

mustangdave

My rearend needs a stud and two nuts.

Founding Member

Feb 26, 2002

2,976

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56

North Carolina

Jun 29, 2007

#12

• Jun 29, 2007

• #12

Gotta love the "wiggle fix".