Motorola 35 amp alternator wiring-is it correct? - JeepForum.com
 
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post #1 of 12 Old 05-08-2021, 05:33 PM Thread Starter
GreyJ20
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Motorola 35 amp alternator wiring-is it correct?

I think I keep blowing out alternators because I am wiring them wrong. I replaced all of the wires in the charging system, checked had good grounds, replaced voltage regulator, ignition switch, and both battery cables. Hereís what I have for alternator wiring.
1. Field terminal (green)
2. Positive lead to battery (yellow)(via the starter)
3. ground (black)
4. Alt cable (red) not sure what this is, but all three wires except the battery positive lead go to the regulator.

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post #2 of 12 Old 05-09-2021, 02:33 AM
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I am pretty sure 3 and 4 are not right, they are not connectors.

The ground for the field should be on the brown block, just below your 1. pic is not clear..

Whether the AUX connection or stator goes is unclear. I expected it to be above 1 in that recess.

Where did you get your wiring details from?

BagusJeep lives in Bali with far too many 4x4s:
1981 CJ7 258ci - Bagusjeep
1984 CJ7 258ci - Puthijeep
1981 J20 258ci - Gladys
1951 Willys CJ3A/MB/M38 - Little Willy
1995 Cherokee 4.0 - CHEROKEE
1980 Land Rover Series III 109" troop carrier - ROVER
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post #3 of 12 Old 05-09-2021, 02:43 AM
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SI that your actual alternator?

Here are a few pics of Motorola alternators from AMC vehicles of the period.
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BagusJeep lives in Bali with far too many 4x4s:
1981 CJ7 258ci - Bagusjeep
1984 CJ7 258ci - Puthijeep
1981 J20 258ci - Gladys
1951 Willys CJ3A/MB/M38 - Little Willy
1995 Cherokee 4.0 - CHEROKEE
1980 Land Rover Series III 109" troop carrier - ROVER
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post #4 of 12 Old 05-09-2021, 02:47 AM
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As I said in our last thread on this, pictures needed of what is ON the jeep. The mysteries old Jeeps throw up can occasionally be solved by close up pictures and testing.

BagusJeep lives in Bali with far too many 4x4s:
1981 CJ7 258ci - Bagusjeep
1984 CJ7 258ci - Puthijeep
1981 J20 258ci - Gladys
1951 Willys CJ3A/MB/M38 - Little Willy
1995 Cherokee 4.0 - CHEROKEE
1980 Land Rover Series III 109" troop carrier - ROVER
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post #5 of 12 Old 05-11-2021, 03:41 PM Thread Starter
GreyJ20
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Quote:
Originally Posted by BagusJeep View Post
SI that your actual alternator?

Here are a few pics of Motorola alternators from AMC vehicles of the period.
Here is the old one that came off the first time I replaced it back in January. There is no place for a field ground wire and neither is there in the wiring harness
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post #6 of 12 Old 05-13-2021, 09:19 PM Thread Starter
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Quote:
Originally Posted by BagusJeep View Post
I am pretty sure 3 and 4 are not right, they are not connectors.

The ground for the field should be on the brown block, just below your 1. pic is not clear..

Whether the AUX connection or stator goes is unclear. I expected it to be above 1 in that recess.

Where did you get your wiring details from?
I think I figured it out, I feel very stupid. I was referencing a picture in my manual that I thought was for the 40 amp but realized the 35 amp and the 40 amp have the same stud placements. So according to the manual then, the AUX red wire should go to the left of the positive lead on the plate with the isolation diode. But I found another picture saying it should go to the right. I think I had the AUX cable on a ground because 3 and 4 are both grounds. Let me know if this makes sense. Note: the regulator wire or AUX wire is now red to match the regulator wiring. Also, middle photo was a photo I found on an AMC Forum I do not believe that the wiring would be correct if it were on this Jeep
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452F4717-0B5F-4808-BCA2-7085A59D47A7.jpg   B163BD5D-1988-4AE5-8E10-F300581E3468.jpg   2BE649BE-0947-4BB7-9E20-2C9914D2931E.jpg  
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post #7 of 12 Old 05-16-2021, 09:00 PM Thread Starter
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Originally Posted by BagusJeep View Post
As I said in our last thread on this, pictures needed of what is ON the jeep. The mysteries old Jeeps throw up can occasionally be solved by close up pictures and testing.
Update: didnít work. Truck still isnít charging. The amp light also no longer comes on
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post #8 of 12 Old 05-16-2021, 09:52 PM
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Looking at the old book and your marked yup alternator, you do not have them on the same bolts/connector.

This look more accurate, using the numbers in your book. (ignore %)
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BagusJeep lives in Bali with far too many 4x4s:
1981 CJ7 258ci - Bagusjeep
1984 CJ7 258ci - Puthijeep
1981 J20 258ci - Gladys
1951 Willys CJ3A/MB/M38 - Little Willy
1995 Cherokee 4.0 - CHEROKEE
1980 Land Rover Series III 109" troop carrier - ROVER
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post #9 of 12 Old 05-18-2021, 08:11 AM Thread Starter
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Originally Posted by BagusJeep View Post
Looking at the old book and your marked yup alternator, you do not have them on the same bolts/connector.

This look more accurate, using the numbers in your book. (ignore %)
I actually did try both number 1 connections in your picture, and that didnít work either. Also, I was told that a blown amp light could not let it charge, I changed the bulb and the connector in the dash and that didnít work either. I also figured the fuse would be the bulb, but that hasnít stopped me from looking
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post #10 of 12 Old 05-19-2021, 12:25 AM
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The way to check the wire that goes to the charge light is to take it off the alternator, turn the ignition on and check for voltage on the end. It should have 7V or so. Or touch it to a ground and the lamp should light up.

The way the lamp works is that in operation there is voltage at both ends, the lamp goes out. When the alternator is off or low output the difference in voltage is enough to light the lamp.

In many such circuits there is a resistor in parallel with the lamp. When the lamp blows the resistor ensures the same voltage in the wire.

The reason is that it is indeed exciting the alternator. Without this there is no operation.

BagusJeep lives in Bali with far too many 4x4s:
1981 CJ7 258ci - Bagusjeep
1984 CJ7 258ci - Puthijeep
1981 J20 258ci - Gladys
1951 Willys CJ3A/MB/M38 - Little Willy
1995 Cherokee 4.0 - CHEROKEE
1980 Land Rover Series III 109" troop carrier - ROVER
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post #11 of 12 Old 05-20-2021, 03:35 PM Thread Starter
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Originally Posted by BagusJeep View Post
The way to check the wire that goes to the charge light is to take it off the alternator, turn the ignition on and check for voltage on the end. It should have 7V or so. Or touch it to a ground and the lamp should light up.

The way the lamp works is that in operation there is voltage at both ends, the lamp goes out. When the alternator is off or low output the difference in voltage is enough to light the lamp.

In many such circuits there is a resistor in parallel with the lamp. When the lamp blows the resistor ensures the same voltage in the wire.

The reason is that it is indeed exciting the alternator. Without this there is no operation.
I did this and got .280 volts at the wire under the hood. The light stayed off. I remembered it suddenly shut off but the battery still wasnít charging
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post #12 of 12 Old 05-21-2021, 03:59 AM
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Then that is part of your problem. You could use a length of wire and a bulb and wire it to teh battery and see if that changes your luck.

BagusJeep lives in Bali with far too many 4x4s:
1981 CJ7 258ci - Bagusjeep
1984 CJ7 258ci - Puthijeep
1981 J20 258ci - Gladys
1951 Willys CJ3A/MB/M38 - Little Willy
1995 Cherokee 4.0 - CHEROKEE
1980 Land Rover Series III 109" troop carrier - ROVER
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