Alternator conversion Question

gubba

Senior Member

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• Mar 8, 2012

• #1

Hi folks..I just finished installing a new alternator in my 67 TR4A.. as per the VTR.org..and I was just wondering why the red dash light stays on when I turn off the key? The install went smooth enough and she fired up right away..I think she liked the new wires..no corrison..I need a better solution then just taking the bulb out..cheers

 

TR3driver

Great Pumpkin - R.I.P

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• Mar 8, 2012

• #2

Either your alternator doesn't work the same as the one used in the article; or the wiring isn't right. Could even be a failure in the altnerator.

 

TR4nut

Yoda

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• Mar 9, 2012

• #3

Electrical is not my area but I was thinking bad alternator - isn't that a sign of a bad diode possibly?

 

Kleykamp

Jedi Trainee

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• Mar 9, 2012

• #4

If the light stays on with the key off, it sounds like its wired wrong and is grounded out. I'm no expert on electrical, but seem to remember that the field had to be set on replacement alternator to positive or negative. If it's backwards that may account for the grounding out. I would not leave the battery connected until the issue is resolved.

 

martx-5

Yoda

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• Mar 9, 2012

• #5

Here's a typical wiring diagram using a Delco 10SI alternator. Yours may not be exactly the same, but the light part of the circuit should be. The idiot light should go ON when the ignition is turned on, and go OFF after the engine starts and the alternator starts charging. As you can see, the light is between the ignition switch and the alternator, so it should never be on with the ignition off. Re-check the wiring.

 

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hondo402000

Darth Vader

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• Mar 9, 2012

• #6

ditto the wiring check, I think you are still sending power to the lamp circuit when the key is in the off position and that would also mean you are sending voltage to the coil when the switch is off, I would use a multimeter put the red lead on the Plus side of the coil, black to ground and check for voltage when the key is off, based on the diagram above, Does the lamp go off when the car is running?

Hondo

 

CJD

Yoda

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• Mar 9, 2012

• #7

Looks like "1" and "2" wires got reversed at the alternator.

John

 

hondo402000

Darth Vader

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• Mar 9, 2012

• #8

you were lucky you didnt fry a wire!

Hondo

 

OP

gubba

Senior Member

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• Mar 9, 2012

• #9

Hi folks..I just checked all the wiring and its okay..Tested the coil with the key of and the light on and it read .50..turned the key on ( the car was not running ) and the light went out and tested the coil and the reading was 10.25. Its a 2 wire alternator #1 white and #2 Red the bigger wire. Its very plain that the wires are not crossed. The bigger Red wire along with the bigger generator wire go to the isulated post on the alternator and the #1 smaller White wire tyes to the small wire from the generator. That being done..from the control box you hook the 2 small Brown/Yellow..Brown/Green wires together and the large Brown/Yellow Brown/White and the 2 Brown/Blue wires all together. You are supposed to disgard the small black ground wire. Anyway something is not right so anything you folks can sujest I will try or I will have to go to Mr. Sparks YUK(big bucks)

 

TR3driver

Great Pumpkin - R.I.P

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• Mar 9, 2012

• #10

gubba said:

Its a 2 wire alternator

Click to expand...

Do you have a part or model number? Some alternators just don't have the output for the warning light. Or it could be a fault with the alternator (eg bad diode or regulator).

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]The bigger Red wire along with the bigger generator wire go to the isulated post on the alternator and the #1 smaller White wire[/QUOTE]
So you've got two terminals (1 and 2) plus a post, right?

 

OP

gubba

Senior Member

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• Mar 9, 2012

• #11

Yes I do Wilson 90-01-3125 61 amp Its like a Delco 7127
https://ws1.wilsonautoelectric.com/ec03/part.php?part_search=90-01-3125&part=90-01-3125

 

OP

gubba

Senior Member

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• Mar 9, 2012

• #12

If you look at this picture you will see a little silver post above the insulated post..This peice I dont no what its for. The black cap is is the plug for the # 1 and # 2 wires.
https://ws1.wilsonautoelectric.com/...hp?w=190&pic=cGFydGltZy85MC0wMS0zMTI1LmpwZw==

 

martx-5

Yoda

Offline

• Mar 9, 2012

• #13

That's a Delco 10SI as I referenced in the wiring diagram that I posted. The small terminal above the Batt terminal is hooked to the stator, supplying about half charging volts. Disregard it.

 

OP

gubba

Senior Member

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• Mar 9, 2012

• #14

Okay so when I look closley at the picture..It looks like a ground wire..so I grounded it but the lite stayed on. I did a parasitic test with the bulb unscrewed and there was no draw..screwed the bulb back in and of coarse there was a very small draw...???

 

TR3driver

Great Pumpkin - R.I.P

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• Mar 9, 2012

• #15

Remove the plug from the alternator, leaving the hot wire to the post connected. Connect an unpowered test light from terminal 1 in the alternator (being careful not to touch the case) to ground. If the test light comes on, the alternator is bad.

If the test light doesn't come on, next step would be to connect the test light from terminal 1 of the plug to ground. If the dash light now comes on with the key off, your dash light is not wired correctly.

 

OP

gubba

Senior Member

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• Mar 9, 2012

• #16

Remove the plug from the alternator, leaving the hot wire to the post connected. Connect an unpowered test light from terminal 1 in the alternator (being careful not to touch the case) to ground. If the test light comes on, the alternator is bad.

Is this with the car running or Just with the key turned on?

 

TR3driver

Great Pumpkin - R.I.P

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• Mar 9, 2012

• #17

Key off, engine not running.

 

TR3driver

Great Pumpkin - R.I.P

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• Mar 9, 2012

• #18

Maybe an explanation of how terminal 1 & the light work will help.

With the key off and the alternator stopped, terminal 1 and both sides of the light should be at ground (so the light is off). When you turn the key on, it applies 12v to one side of the light, so current flows through the light and into terminal 1, where it provides a small amount of current through the regulator into the rotor of the alternator, to get it started working.

Once the engine is started and the alternator begins to produce some output, the diode trio takes over and supplies 12v (approx) to terminal 1 (and the regulator/rotor). Since the light now has 12v on both sides, it goes out.

 

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OP

gubba

Senior Member

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• Mar 10, 2012

• #19

Randal..Ive got the same setup in my 3B and it works fine. I did take the plug out and test with the light ( as per your instuction)and the light came on. I am going to do the same test on my 3B to see what happens. I'll get back to you.

 

OP

gubba

Senior Member

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• Mar 12, 2012

• #20

Hi folks...Now that I'm a geneious on alternators..Thanks to you guys..I'll tell you what the problem was. ( Basil) FAULTY alternator. Took it in to be bench tested and low and behold NO NADA..So I took it back and got another one which I just inslalled..and wala..the light went out when I turned the key off. Now my question to you all is.. WHY CAN IT NEVER BE DONE ONCE!!!!!