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Old 02-27-2011, 06:14 PM
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Alt shorted

Recently I followed Doc's diagram and switched my external regulator over to a new internal reg/alt...... installed it and got 14.6 volts across the batt when running.... all is good. 2 days later the battery is flat, charged it up, charger said batt bad, battery was less than 2 wks old. Replaced battery, noticed cable end was just about busted thru, replaced cable, while replacing cable laid hand on alt......... It was too hot to touch! (no the car wasn't running)

My question: is there any way to short the alt out by hooking the wires up wrong?

10 gage wire from batt lug on alt to the horn relay buss
10 gage wire from the horn relay buss to the batt (as Doc suggested)
New pig tail wire from alt to idiot light and the other to switched 12V

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Old 03-03-2011, 05:45 PM
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Pulled the alt had it tested..... it's charging

Did a cont check on the wires......
white wire from the alt is switched 12v
Red (old color blue) has cont with ground..... this is the wire that's connected to the idiot light

Is this what's causing the alt to short out and get hot?
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Old 03-03-2011, 06:05 PM
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Quote:
Originally Posted by EOD Guy
Pulled the alt had it tested..... it's charging

Did a cont check on the wires......
white wire from the alt is switched 12v
Red (old color blue) has cont with ground..... this is the wire that's connected to the idiot light

Is this what's causing the alt to short out and get hot?
What kind of alternator gm ford chrysler?
could you post a pic of the diagram?
Could be a bad diode in the alternator.
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Old 03-03-2011, 06:27 PM
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Check all your connections and wiring diagram again. The juice is going somewhere and killing the battery and the alternator is getting hot trying to charge it all back up.

bad connection, grounds or wrong connection..
http://www.oldengine.org/unfaq/10si.htm
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Old 03-04-2011, 06:21 PM
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Looks like it's going to be the voltage reg...... purchased a cheapo alternator from Adv Auto....... seems to be fine, not getting hot etc...... who would have thought a brand new hi dollar alt would be bad right out of the box.

Last edited by EOD Guy; 03-04-2011 at 06:33 PM.
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Old 03-04-2011, 06:41 PM
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Thanks for the feedback. At least it didnt cook anything else.
I was just telling someone else who had a question about what a good brand of electronic parts were for his GM. naturally ac delco is what you want, but napa was mentioned...good stuff, borg warner has proved to be sketchy and cardone is pretty much the botoom of the barrel.even bosch has been getting not so much a dependable sure thing.
What brand was the alternator?
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Old 03-04-2011, 07:37 PM
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Quote:
Originally Posted by EOD Guy
Pulled the alt had it tested..... it's charging

Did a cont check on the wires......
white wire from the alt is switched 12v
Red (old color blue) has cont with ground..... this is the wire that's connected to the idiot light

Is this what's causing the alt to short out and get hot?

Here's the diagram.



I don't know what color wires you have, but the wire going to terminal no. 1 on the alternator goes to the idiot light. The wire going to terminal no. 2 goes to the junction block, not switched power. The wire from the threaded BATT stud also goes to the junction block.
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Old 03-05-2011, 03:53 AM
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Joe, as mentioned in #1 post I used Doc's diagram, same as the one you posted, but as Doc and others suggested, if the main batt wire goes to the Radiator support junction instead of the OEM splice or horn relay buss bar, I lose the benefit of the resistance (and buffering effect) of the long wire vs a shorter wire which would heat up etc….

I stated switched 12v .... should have said constant 12v

Last edited by EOD Guy; 03-05-2011 at 04:04 AM.
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Old 03-05-2011, 08:21 AM
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Quote:
Originally Posted by EOD Guy
Joe, as mentioned in #1 post I used Doc's diagram, same as the one you posted, but as Doc and others suggested, if the main batt wire goes to the Radiator support junction instead of the OEM splice or horn relay buss bar, I lose the benefit of the resistance (and buffering effect) of the long wire vs a shorter wire which would heat up etc….
When I said "junction block", I meant the one on the horn relay. In any case, there's no "heating up" issue. On the SI family alternators, it is preferred to run the wire from the #2 terminal all the way to the junction block to properly sense system voltage after accounting for resistance in the wire, but the alternator will work fine even if you simply run a short wire from the #2 terminal to the BATT post on the alternator. This is how I set up the alternator in my 62 Olds and it charges just fine. The stock SI alternators are extremely easy to wire up. If you are using the stock wires in the car and installing jumpers at the old voltage regulator connector, then be sure the stock wires actually go where they are supposed to. People have a way of monkeying with wires over the years and making "destructive improvements". Personally, I'd just run new wires from the alternator.
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Old 03-05-2011, 08:55 AM
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Ok I'm not stupid, There was a heating up issue, it got so hot I couldn't put my hand on it, it wasn't due to the way I wired it up because with a new Alt installed exactly the same way as the old..... no heating up issue and since the old, faulty one was charging, my best guess would point to the voltage regulator.
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Old 03-11-2011, 06:24 PM
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Best guess was wrong! It ended up being the wires from the alt (terminals 1&2) shorting out as they passed thru the radiator support and ran across the support to the horn relay. There was a grommet and tape, which I decided to check, and low and behold the guy before me didn't do such a good splice job! The wires were cut at some point and spliced back together, the tape had worn between them and an intermitent short developed. Got it properly spliced and all seems to be fine now.
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Old 03-11-2011, 06:35 PM
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Thats messed up. I splice by doing a linemans twist and shrink wrap after It is soldered.Usually with good results.
Some of the biggest messes are the stereo guys + alarm system guys.
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Old 03-12-2011, 05:53 PM
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After inspecting several tape balls.....looks like I'm going to end up getting a new wire harness from painless..... did'nt want to untill I got my new motor but......
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