Alternator Wiring Help!
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Alternator Wiring Help!
I recently bought a 1972 F-100 with a 351 Windsor (from a 1977 LTD II). I took out the altenator and tried to replace with a new one, but the connections do not match. On the old altenator, there are two snap-on wires (one white and the other red/orange) and one thick battery wire. These three wires come out of a thick rubber junction with a connector at the base. On the original, these three wires were hooked, but the connector at the base was not connected to anything.
Now, on the new altenator, there are two snap-on connectors (one white and the other black) and there is a red battery connector. There are also two other ports...one says it's ground.
So, what I did was snap the white to white...the red/orange to black,,,and the thick battery cable to the red BAT connection. The connector at the base of the black rubber junction is still not connected to anything.
Probably unwisely, I tried this and the motor runs, but the "ALT" light is on. I haven't tested to see if it's charging...wanted to make sure it's hooked up right first.
Any help here would be greatly appreciated.
Now, on the new altenator, there are two snap-on connectors (one white and the other black) and there is a red battery connector. There are also two other ports...one says it's ground.
So, what I did was snap the white to white...the red/orange to black,,,and the thick battery cable to the red BAT connection. The connector at the base of the black rubber junction is still not connected to anything.
Probably unwisely, I tried this and the motor runs, but the "ALT" light is on. I haven't tested to see if it's charging...wanted to make sure it's hooked up right first.
Any help here would be greatly appreciated.
Fleet Mechanic
Joined: May 2001
Posts: 1,396
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From: Cupertino
Confusing, but I will try.
If your ALT light is not, you are not charging. You can verify this by checking the battery voltage while the engine is running over 1000 rpm. You should read in the high 13's.
One of the wires coming out of the rubber junction is FIELD. Remove battery cable, take an ohmmeter and find the field connection on the side of the voltage regulator. Verify continuity to the alternator side of the connector and put this to the field terminal of the alternator. The big wire is BAT and runs to the battery terminal on the solenoid on the fender well. The third wire is ground.
Make sure the connector is tightly pressed into the regulator.
My suspicion is that you have mixed up the ground and field connections and the alternator is not grounded.
It wouldn't hurt to run another ground wire directly from the alternator case to the block. A few days ago a smart guys wrote a nice posting about grounds and their importance to the charging system. Have a look back in the postings.
Good luck.
Semper Fi
If your ALT light is not, you are not charging. You can verify this by checking the battery voltage while the engine is running over 1000 rpm. You should read in the high 13's.
One of the wires coming out of the rubber junction is FIELD. Remove battery cable, take an ohmmeter and find the field connection on the side of the voltage regulator. Verify continuity to the alternator side of the connector and put this to the field terminal of the alternator. The big wire is BAT and runs to the battery terminal on the solenoid on the fender well. The third wire is ground.
Make sure the connector is tightly pressed into the regulator.
My suspicion is that you have mixed up the ground and field connections and the alternator is not grounded.
It wouldn't hurt to run another ground wire directly from the alternator case to the block. A few days ago a smart guys wrote a nice posting about grounds and their importance to the charging system. Have a look back in the postings.
Good luck.
Semper Fi
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Thanks. I tried grounding it, but it's still not charging. I wonder if the two snap-on connectors are reversed? Right now I have the white (w/ black stripe) wire going to the white terminal on the new altenator...and I have the orange wire going to the Black terminal on the altenator.
Fleet Mechanic
Joined: May 2001
Posts: 1,396
Likes: 4
From: Cupertino
All I have to work with is the '67 manual. I am looking at fig. 1 of the charging system system for the Autolite alternator system. It shows the attachments to the regulator :
white wire (field) (F) goes to alternator
white-black (stator) (S) goes to alternator
yellow (battery voltage) (A) directly to battery +
green-red stripe (Indicator light) (I) This connection is left open on the regulator for vehicles with ammeters
You have to check continuity from the F on the regulator to F on the alternator.
Then check to see that the I terminal on the regulator goes to the light.
Then check for 13.5-13.8 volts at the battery terminal at fast idle. You may be charging and the indicator circuit is not right.
This is the best I can do for you, Buddy.
Anybody have a '72 manual to help out?
white wire (field) (F) goes to alternator
white-black (stator) (S) goes to alternator
yellow (battery voltage) (A) directly to battery +
green-red stripe (Indicator light) (I) This connection is left open on the regulator for vehicles with ammeters
You have to check continuity from the F on the regulator to F on the alternator.
Then check to see that the I terminal on the regulator goes to the light.
Then check for 13.5-13.8 volts at the battery terminal at fast idle. You may be charging and the indicator circuit is not right.
This is the best I can do for you, Buddy.
Anybody have a '72 manual to help out?
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Thanks very much for your help. I believe I've got enough info to figure it out now. I'm pretty sure I have the two snap-on wires backwards...white to white was a bad assumption. Also, the connector at the base of the junction is probably a radio noise capacitor and needs to go to ground.
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