Electrical challenge

[LMBoise]

So I am converting my ‘48B to a negative ground, alternator system. I am using a previous  members diagram as a guide, see attached photo. My challenge is, when after  turning over the engine for several turns, the ground wire from the alternator to the frame starts to smoke and smolder.

 

Here is what I have:

delco 10si alternator

wire from the negative side of the amp meter to the positive on the alternator 

with a double wire plug on the alternator, see pic, I have the red wire going back to the positive on the alternator and a wire going to the coil that has a one way diode. 
a black wire, not shown, going from the ground bolt on the alternator to the frame (properly sanded to bare metal on frame)

Wire from the positive terminal on the battery to the  starter 

Wire from the starter to the positive on the amp meter

Negative from the battery grounded to the frame, but no grounding wire from the engine to the frame. 

 

Any ideas on what I have done wrong? It is a new alternator with a 30 amp in line fuse on the wire to the alternator from the amp meter. The fuse has not blown. 
 

Thanks!

[maok]

As per wiring diagram, you only need ONE wire from the alternator to the ammeter, nothing else needs to be wired to the alternator, even the ground wire is not needed, already grounded from the bracket.

 

The double plug is not used. And not sure why you would have it wired to the coil.

 

[JBNeal]

Convert a starter mounting bolt to a mounting stud and route a new ground cable from the battery to that starter mounting stud.

[kencombs]

Sounds like that is the only ground the starter current has back to the battery.  Do you have an engine to frame ground?  If not add one.

 

edit:   JBN and I were typing at the same time and he's faster.

 

I've even seen choke cables burn up due to lack of any other engine to frame ground!

Edited October 10, 2022 by kencombs

[LMBoise]

Thanks for the quick feedback. Will give that a go tomorrow. 
 

I was also going on this YouTube video from Vintage Auto. They talked about the plug and the wire to the coil or some other not source. As you can tell, the electrical is not my expertise, but the video talks about that wire as a “sense” wire. If I hear everyone correctly, I can just ditch the two wire plug and stick with just the wire from the amp meter. I will also add an engine to frame ground.  
 

Thanks again! 

[LMBoise]

Forgot to attach the video. 
 

 

[Merle Coggins]

I agree with Ken and Brian. It sounds like you don't have a good ground for the for the engine block and your alternator ground wire is trying to carry all of the cranking current. Where do you have your battery ground cable attached? Originally they went to the transmission case, using one of the top cover bolts. This provided an adequate ground path when everything is new. But if the mount between engine and trans is no longer clean and tight you may be loosing a good ground back to the battery. I have also added a good ground cable between the engine block and the frame to ensure a good ground for the chassis even though it's probably not "factory".  

[LMBoise]

I have the battery ground attached to the frame. During the restoration I had the frame powder coated, but sanded off the area where I attached the ground. It sounds like I need to ground the engine block to the frame and maybe change my battery ground to the transmission or to the starter bolt as JBN recommends. Also, is the consensus I should ditch the two wire plug on the alternator? 
Thanks. 

[Plymouthy Adams]

the two plug wire when wired properly allows immediate charging and not having to rev the engine to energize...second, the sense as close to battery as can be connected senses battery conditions and ensure proper charging rate....many out of simplicity just ignore these wires on retrofit....seldom do any install a charging indicator light so the KISS practice is applied. 

[LMBoise]

Sounds good to me, thanks! 

[lostviking]

I looked the the manual for the Delco 10SI alternator you mentioned. As I see it, the only connections you should be using, per the wiring diagram you attached, are the OUTPUT lead to the Amp meter and the ground leads. Those, as I think others have stated indirectly are only there for a better ground signal to the alternator. They were never intended to carry all the return current. As previously stated, get a heavy duty ground strap from the engine to the frame/battery. I would probably just use the frame myself as you have that done already. BUT you need to connect the engine, which is the ground for heavy currents from the alternator.

[LMBoise]

Thanks for looking that up. I have a ground strap on order and will ground the engine to the frame. I appreciate all of the feedback! 

[greg g]

A ground strap from the body to the frame or engine is probably  good idea too.