Alternator/burned wire

[Todd Wilson]

Had a problem with the old 74 Dodge truck yesterday. Its the same wiring as my 71 Charger so I thought I would ask here and get some ideas on the cause.

Went out to start truck. Battery was very weak but did get the truck to start. Alternator not charging. Assumed bad diodes in alt. as I have had this happen before. Was kinda pissed as this was a store bought alternator and was only about a year and a half old. I dont normally buy alts. and starters from parts stores but it went out during a winter storm and I needed to replace fast.  Anyways I stop by my parts store and bitch about the alt. and they give me a new one to replace it.  I get home and swap the alt. and go to fire up the truck and it wont start. Motor turns over but acting like it has no spark and then suddenly I got smoke.   SO far it appears the red wire on the field by the alternator burned  and then it appears ot have burned again on the bend of the engine hardness as it goes around the back of the motor kinda by the volt reg.   Another wire under the dash coming from the bulkhead that goes up into the steering column really smoked.  It appears a section of this wire has been replaced by the previous owner.  The bulkhead connector is fine and actually appears to be clean and in good shape.


So what has caused this problem?   Did I get a bad alt.  (it will be checked after I pull it off)  or do I have a wiring issue that killed the first alt. and then smoked the wiring with the new alt. since it was fresh and ready to go.

Was wondering if someone has had a similair problem and give some ideas on what to check.

Todd

[The70RT]

Sounds like the wire that was previously replaced by the other owner grounded out 

[Todd Wilson]

Thats possible. So far tracing the schematic  the 16RE leaves the alternator and was burnt some right there and it goes around thru the engine hardness where it splits to either the volt reg. or ballast resister or continues thru the bulkhead up into the column to the ignition switch.This is where the splice is and was the wire that burnt the most compared to the others. Something obviously grounded out preventing juice to get far enough to give me spark yet smoked some wires. As of right now I think I lost one wire in the harness unless it melted others under the tape.

The altenator that was thought to be bad tested good today at the store. The NEW alternator is still unknown as its raining today and didnt want to pull it.

[l8rg8r]

my 73 power wagon smoked a alt wire from the alt to the ign switch and what caused that was the blue field wire was grounding to the alt body at the post on the back of the alt the little ceramic isolator was broken from the post being to tight

[Todd Wilson]

my 73 power wagon smoked a alt wire from the alt to the ign switch and what caused that was the blue field wire was grounding to the alt body at the post on the back of the alt the little ceramic isolator was broken from the post being to tight

Thanks for that info. This is puzzling now. Makes no sense. Only thing new in the mix is the new alt. I will check it tomorrow.


Todd

[Nacho-RT74]

my 73 power wagon smoked a alt wire from the alt to the ign switch and what caused that was the blue field wire was grounding to the alt body at the post on the back of the alt the little ceramic isolator was broken from the post being to tight

that was EXACTLY what I was to say!!!!

just that the brush isolator is not ceramic, is plastic

[Todd Wilson]

OK so is this possble over tightening  on one of the 2 field connectors inside the alt?  Or is it the big wire  that has the nut and plastic cover?  I wonder if this isnt my problem.


Todd

[John_Kunkel]

If the operator doing the test is unfamiliar with the Mopar dual field alternator it can test OK but still be bad. The test machine puts 12V to one field and grounds the other, if the tester hooks the 12V lead to the same field you had the power going to it will show a short but if he reverses the way you had it hooked up and the other field is shorted to ground it will test OK on the machine. 50/50 odds.

A good operator will run the test with the field connectors in both positions.

[Todd Wilson]

If the operator doing the test is unfamiliar with the Mopar dual field alternator it can test OK but still be bad. The test machine puts 12V to one field and grounds the other, if the tester hooks the 12V lead to the same field you had the power going to it will show a short but if he reverses the way you had it hooked up and the other field is shorted to ground it will test OK on the machine. 50/50 odds.

A good operator will run the test with the field connectors in both positions.

I am betting this may be my problem. Put the new alt on and got smoke. Is there a way to test an alt before putting on to avoid this situation? Could one check continuity from the alt. chassis and each field spade connector?  My parts store is telling me theres no way possible for a alt. to smoke my wires that its the old trucks fault.


Todd

[Todd Wilson]

The alt. was indeed bad.   Took it bck to the store for testing and it was FUBAR'd on their tester.  They asked what they needed to do. I said a new alt. and a wire harness for the truck.   I'm getting a new alt.........and I get to fix my truck wiring on my own.   


Todd