Re: 1972 Eldorado wiring harness

[Stoverlarry]

Need some help here I am working on a 72 cad Eld so many wires have been cut and by passed I put a new alternator on and now I can't get any fire out of the coil.

[The Tassie Devil(le)]

G'day Larry,

I have moved your question to a new heading on its' own as the old thread was simply that, old.

I take it that you don't have a Shop Manual.

Changing the Alternator shouldn't have caused your current problem, o can you describe just what you did?

Any pictures?

Bruce.

[35-709]

You just can't go wrong buying a Cadillac Shop Manual for your car ---

https://www.ebay.com/itm/1972-CADILLAC-SHOP-MANUAL/192587883935?hash=item2cd721e59f:g:CyEAAOSwRqBbO5zZ

https://www.ebay.com/itm/1972-Cadillac-Shop-Manual/302779431961?hash=item467f0f7c19:g:X2wAAOSwCDZa~G5Q

Buy the Fisher Body Manual too ---

https://www.ebay.com/itm/1972-CHEVROLET-PONTIAC-OLDSMOBILE-CADILLAC-BUICK-BODY-SHOP-MANUAL-ORIGINAL-BOOK/132699831597?hash=item1ee586bd2d:g:PEcAAOSwLF1X40gw

[Stoverlarry]

I just replaced alternator and wire that goes to the plug on the top of the alternator the one runs across the top of the engine is a new wire and there was two other wires there that were cut coming from the bulkhead laying on the valve cover and then put a new coil on there  ignition coil on that side of the motor I have the resistor wire and another wire that goes to the  positive it was barely idling until I done that now I have no spark going to distributor checked all fuses are all good I had to order a manual won't be here for a week

[TJ Hopland]

There are 4 different alternators that will more or less bolt in there so lots of chances for someone to have swapped them at some point.   72 I think was the last year for the external regulator so the wiring for those would be a lot different than the 10si or 12si internal regulator or a 'single wire' conversion.    The external regulator alternators had the small 2 wire plug sticking out the back with the pins flat side to flat side.   The internal regulator had them sticking out the side and were narrow side to narrow side.

The reason alternators get tangled up with ignition is they both get a key on circuit.  When people start doing swaps this common connection can end up back feeding the ignition so the engine doesn't turn off with the key.   Instead of admitting they don't know what they are doing and getting help one way or another they come up with more hacks to try and work around the problem.

[Stoverlarry]

Oh boy I don't even know where to start now maybe that explains I bought a new battery 2 days later it was dead when I went to start the car

[Stoverlarry]

I don't know how to send a picture through this site it would probably help two more explain what I got I dunno when I turn the key on my ignition coil has 12 volts when I turn it off it goes to zero

[Stoverlarry]

And I only have one wire that goes across the valve cover to the Bulkhead from the alternator

[The Tassie Devil(le)]

I don't know how to send a picture through this site it would probably help two more explain what I got

When you reply to a post, at the bottom of the typing box is the words "+ Attachments and other options".
Open that, and at the bottom is "Attack" and you can choose the picture you want from your computer file in the "Choose File".

You can add up to 10 pictures by pressing on (more attachments)

Bruce.

[Stoverlarry]

I'm not on a computer I'm on a tablet

[Stoverlarry]

Should there be 12 volts going to the coil and then I was told at the parts store that I need it to put the positive on the negative and negative on the positive haven't done that yet little sketchy about that

[Stoverlarry]

Here

[TJ Hopland]

One small wire to the alternator kinda sounds like the internal regulator setup.   Can anyone confirm was a 72 supposed to be internal or external?     Does the alternator you currently have have the small wire connector out the back or out the side?

Your battery going dead could be for 2 alternator related reasons.    #1 is that its not charging likely because the regulator isn't being turned on.   #2 is the regulator is being left on when the engine isn't running so its draining the battery. 

Do you know if you still have points in the distributor?  Just one wire coming out of the bottom or is there 2? 

No idea what they are getting at about the coil.    The + terminal is a + and basically is live when the key is on.   Turning the key off it goes dead and the engine stops.  There is more to it than that but at this stage that is all that is important.  The - terminal goes to the points in the distributor though that single wire.  The points close and ground to the engine to complete the circuit.         

[Stoverlarry]

I do have one wire coming out of the distributor and the points look good and I change the two wires around on the alternator last night and my battery is still good I'm sure I'm supposed to have 12 volts going to the coal right

[TJ Hopland]

I just missed the photos on the last reply.     

You do have the internal regulator alternator.   It looks to be connected correctly at the alternator.   Jumper wire from the stud to the terminal farther from the stud is correct.    The other wire needs to be +12 when the key is on.   On factory cars with the internal regulator this goes through the GEN light before it goes to a key on fuse.    If you check that wire with the key off it should not show any voltage.   If its showing voltage that means the regulator is on and it will drain the battery.   I don't know if yours had an external regulator or not.   IF it did there are some specific mods needed to go internal.

On the coil I think I see a non factory crimp connector that has 2 wires in it.  This is likely the + terminal on the coil.   It should show +12 with the key on.     - on the coil goes to the single wire out the bottom of the distributor. 

[Stoverlarry]

Okay the wire that runs from the alternator to the bulkhead when keys off no voltage keys on no voltage my wires that run to the positive of the coil no voltage until I turn the key when I put the hot wire on the coil the voltage drops to 5.62

[Stoverlarry]

Do you see anything wrong here

[Stoverlarry]

I'm getting 2.5 volts with the key on for the wireless coming out of the alternator to the Gen light

[Stoverlarry]

I meant wire not wireless sorry

[The Tassie Devil(le)]

I will be checking what mine looks like today, and report back.

But, the normal voltage to the + side of the coil should be something like 8 Volts, and should only be 12 Volts when the Starter Motor is cranking.   This 12 Volts is coming from the R terminal on the Starter Solenoid, and the lesser voltage from the resistance wire to the Ignition Switch.

Bruce.