Alternator Question

7173Mustangs.com

Help Support 7173Mustangs.com:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
G

goodnigh

Well-known member
7173 Mustang Supporter Member
Joined
Apr 19, 2011
Messages
4,308
Reaction score
64
Location
San Jose, CA
My Car
1971 M-code Grande
When I use the turn signal the headlights dim, same with the cockpit

fan, etc. I am thinking I need a new alternator. The battery is less

than one year old and regulator was recently replaced. The one now

installed is ~65 amp(?) and don't know how old but not factory

original. I assume installing a 100 amp unit is not a problem. The

question is do I need one with single wire and internally regulated?

Summit Racing has one for $105 and NPD for $265.

mike

 
From the factory, most our Mustangs were equipped with an Autolite 55 AMP alternator that ist externally regulated. The regulator is a box located on the right fender apron, close to the starter solenoid.

Converting the car to an internally regulated alternator with a one-wire hookup is possible. The stock regulator will then have to go.

Under normal driving conditions and with standard equipment, the car does not need 100 AMP to properly operate. If you have added power equiment and large stereo amplifiers, 100 AMP and more can make sense.

To check the alternator performance and regulator condition do the following:

Start the car and bring it to operating temperature. Hook up a Voltmeter to the alternator circuitry. Turn on as many power consumers in the car as possible, headlights, high-beam, blower, radio, interior lights, ...

Observe the voltage. If it goes down significantly from 14 Volts, chances are high that your alternator or regulator are shot. If the fluctuation is only small, the regulator may be defective. Sometimes, mechanical regulators (used by Ford back then) begin to operate faulty when aging. They cannot compensate for quick changes in power demand any more.

I had this twice on Ford cars. I fixed it by using an electronic regulator of high quality.

 
Last edited by a moderator:
Unfortunately the replacements for our stock external regulators suck. They are the typical china made crap. I converted to an 95 amp internal regulated alternator and never looked back. Not a single issue since.

 
From the factory, most our Mustangs were equipped with an Autolite 55 AMP alternator that ist externally regulated. The regulator is a box located on the right fender apron, close to the starter solenoid.

Converting the car to an internally regulated alternator with a one-wire hookup is possible. The stock regulator will then have to go.

Under normal driving conditions and with standard equipment, the car does not need 100 AMP to properly operate. If you have added power equiment and large stereo amplifiers, 100 AMP and more can make sense.

To check the alternator performance and regulator condition do the following:

Start the car and bring it to operating temperature. Hook up a Voltmeter to the alternator circuitry. Turn on as many power consumers in the car as possible, headlights, high-beam, blower, radio, interior lights, ...

Observe the voltage. If it goes down significantly from 14 Volts, chances are high that your alternator or regulator are shot. If the fluctuation is only small, the regulator may be defective. Sometimes, mechanical regulators (used by Ford back then) begin to operate faulty when aging. They cannot compensate for quick changes in power demand any more.

I had this twice on Ford cars. I fixed it by using an electronic regulator of high quality.
Click to expand...
With engine at idle the voltage at the battery reads 13.72, with

everything turned on it reads 13.18 and this is the regulator currently

installed from Marti Auto

http://www.martiauto.com/itemselection.cfm?item=VR-5&selecteditem=yes

mike

 
From the factory, most our Mustangs were equipped with an Autolite 55 AMP alternator that ist externally regulated. The regulator is a box located on the right fender apron, close to the starter solenoid.

Converting the car to an internally regulated alternator with a one-wire hookup is possible. The stock regulator will then have to go.

Under normal driving conditions and with standard equipment, the car does not need 100 AMP to properly operate. If you have added power equiment and large stereo amplifiers, 100 AMP and more can make sense.

To check the alternator performance and regulator condition do the following:

Start the car and bring it to operating temperature. Hook up a Voltmeter to the alternator circuitry. Turn on as many power consumers in the car as possible, headlights, high-beam, blower, radio, interior lights, ...

Observe the voltage. If it goes down significantly from 14 Volts, chances are high that your alternator or regulator are shot. If the fluctuation is only small, the regulator may be defective. Sometimes, mechanical regulators (used by Ford back then) begin to operate faulty when aging. They cannot compensate for quick changes in power demand any more.

I had this twice on Ford cars. I fixed it by using an electronic regulator of high quality.
Click to expand...
With engine at idle the voltage at the battery reads 13.72, with

everything turned on it reads 13.18 and this is the regulator currently

installed from Marti Auto

http://www.martiauto.com/itemselection.cfm?item=VR-5&selecteditem=yes

mike
Click to expand...
Mike the original looking style concours regulators are very ground sensitive

I see you bought one on my web site, thank you

But as you drive your car daily and have the CA heat - you might be better off with the electronic ones from an auto parts store - you can always paint it blue and get the yellow decal.

It will not be correct but won't be real noticeable if it is dressed up.

Let me know and I can cancel the order if you go the electronic route.

Don

 
Mike the original looking style concours regulators are very ground sensitive

I see you bought one on my web site, thank you

But as you drive your car daily and have the CA heat - you might be better off with the electronic ones from an auto parts store - you can always paint it blue and get the yellow decal.

It will not be correct but won't be real noticeable if it is dressed up.

Let me know and I can cancel the order if you go the electronic route.

Don
Click to expand...
No, complete the order. It is better than taking the car to a local

garage. Horror of Horrors!

A drop from 13.8 to 13.1 is not good at idle. If the regulator is not

the problem we will move on.

mike

 
Another issue often overlooked is if the alternator belt is not tight. At idle, a loose belt will slip, allowing the alternator not to put out as much voltage as needed to charge the battery. With the engine at running RPMs, the alternator will spin enough to be good.

 
Hey Mike,

Is this something new that it's doing or has it done it forever?

My interior light would dim when I turned on headlights, and everything blinked with the turn signal on.

I'm thinking that a higher output alternator might help, but may not solve the issue.

There is just a huge amount of draw when you turn on the lights because of how they were factory wired.

I ended up putting my headlight power through a relay pack, and used the switch only to trip the relays.

My headlights are way brighter and nothing dims or flickers anymore.

I did pretty much this:

http://www.midnightdsigns.com/james/headlights.htm

It might not solve your issue, but worst case is it will definitely make your headlights brighter.

 
To remove a large load from the headlight switch I used this premade harness as it was less than the cost of buying all the components and works perfectly.

A fresh headlight switch is a good idea as they tend to be problematic to some degree. These two things cured most of my dimming issues.

I intend to go 3G fairly soon, but I have to finish and recover from ongoing projects first.

 
You havent tried a new headlight switch? I think i replaced the one in my high school 72 when it was not too old, and the oem one in my current 72 that was a joke. Look inside one and you will see why you should replace it. Keep it for old time sake but the ceramic/metal spring resistor is almost flintstones....oxidation prevents long term operation. Swap it out and see if it solves some problems!

 
Hello Jeff,

Can you provide the link where you got the headlight harness?

mustang7173

To remove a large load from the headlight switch I used this premade harness as it was less than the cost of buying all the components and works perfectly.

A fresh headlight switch is a good idea as they tend to be problematic to some degree. These two things cured most of my dimming issues.

I intend to go 3G fairly soon, but I have to finish and recover from ongoing projects first.
Click to expand...
 

Similar threads

J
Need help alternator problem
Replies
10
Views
850
rcadd1ct
R
73inNH
Hunting a voltage leak
Replies
18
Views
1K
giantpune
G
SalmonTex
Help Locating a Dead Short
Replies
8
Views
458
mrgmhale
mrgmhale
M
Replacing externally regulated alternator with one-wire internally regulated alternator
Replies
2
Views
1K
mkrazy127
M
C
Parts For Sale Batch number 2, 351C lift hooks, water pump pulley, alternator brackets, a/c bracket, headlight bezels/trim rings, fenders, RH dash closeout, +more
Replies
0
Views
422
cwalker509
C

Latest posts

Back
Top